29 CFR part 1910, subpart Q

Occupational Safety and Health Admin., Labor

§ 1910.251

(iii) There shall be one of the following at all openings in the blade enclosure intended for the discharge of
grass:
(a) A minimum unobstructed horizontal distance of 6 inches from the end
of the discharge chute to the blade tip
circle.
(b) A rigid bar fastened across the
discharge opening, secured to prevent
removal without the use of tools. The
bottom of the bar shall be no higher
than the bottom edge of the blade enclosure.
(iv) Mowers shall be provided with
stops to prevent jackknifing or locking
of the steering mechanism.
(v) Vehicle stopping means shall be
provided.
(vi) Hand-operated wheel drive disengaging controls shall move opposite
to the direction of vehicle motion in
order to disengage the drive. Foot-operated wheel drive disengaging controls
shall be depressed to disengage the
drive. Deadman controls, both hand
and foot operated, shall automatically
interrupt power to a drive when the operator’s actuating force is removed,
and may operate in any direction to
disengage the drive.

(iii) After the load has been raised, it
shall be cribbed, blocked, or otherwise
secured at once.
(iv) Hydraulic jacks exposed to freezing temperatures shall be supplied with
an adequate antifreeze liquid.
(v) All jacks shall be properly lubricated at regular intervals.
(vi) Each jack shall be thoroughly inspected at times which depend upon
the service conditions. Inspections
shall be not less frequent than the following:
(a) For constant or intermittent use
at one locality, once every 6 months,
(b) For jacks sent out of shop for special work, when sent out and when returned,
(c) For a jack subjected to abnormal
load or shock, immediately before and
immediately thereafter.
(vii) Repair or replacement parts
shall be examined for possible defects.
(viii) Jacks which are out of order
shall be tagged accordingly, and shall
not be used until repairs are made.
(b) Abrasive blast cleaning nozzles. The
blast cleaning nozzles shall be equipped
with an operating valve which must be
held open manually. A support shall be
provided on which the nozzle may be
mounted when it is not in use.

[39 FR 23502, June 27, 1974, as amended at 43
FR 49750, Oct. 24, 1978; 49 FR 5323, Feb. 10,
1984; 50 FR 4649, Feb. 1, 1985; 61 FR 9240, Mar.
7, 1996]

[39 FR 23502, June 27, 1974, as amended at 49
FR 5323, Feb. 10, 1984]

§ 1910.244 Other
equipment.

portable

tools

Subpart Q—Welding, Cutting and
Brazing

and

(a) Jacks—(1) Loading and marking. (i)
The operator shall make sure that the
jack used has a rating sufficient to lift
and sustain the load.
(ii) The rated load shall be legibly
and permanently marked in a prominent location on the jack by casting,
stamping, or other suitable means.
(2) Operation and maintenance. (i) In
the absence of a firm foundation, the
base of the jack shall be blocked. If
there is a possibility of slippage of the
cap, a block shall be placed in between
the cap and the load.
(ii) The operator shall watch the stop
indicator, which shall be kept clean, in
order to determine the limit of travel.
The indicated limit shall not be overrun.

AUTHORITY: Secs. 4, 6, and 8 of the Occupational Safety and Health Act of 1970 (29
U.S.C. 653, 655, 657); Secretary of Labor’s Orders 12–71 (36 FR 8754), 8–76 (41 FR 25059), 9–
83 (48 FR 35736), 1–90 (55 FR 9033), or 6–96 (62
FR 111), as applicable; and 29 CFR part 1911.
SOURCE: 55 FR 13696, Apr. 11, 1990, unless
otherwise noted.

§ 1910.251

Definitions.

As used in this subpart:
(a) Welder and welding operator mean
any operator of electric or gas welding
and cutting equipment.
(b) Approved means listed or approved
by a nationally recognized testing laboratory. Refer to § 1910.155(c)(3) for definitions of listed and approved, and
§ 1910.7 for nationally recognized testing laboratory.

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§ 1910.252

29 CFR Ch. XVII (7–1–05 Edition)

(c) All other welding terms are used
in accordance with American Welding
Society—Terms
and
Definitions—
A3.0—1969, which is incorporated by
reference as specified in § 1910.6.
[55 FR 13696, Apr. 11, 1990, as amended at 61
FR 9240, Mar. 7, 1996]

§ 1910.252 General requirements.
(a) Fire prevention and protection—(1)
Basic precautions. For elaboration of
these basic precautions and of the special precautions of paragraph (a)(2) of
this section as well as a delineation of
the fire protection and prevention responsibilities of welders and cutters,
their supervisors (including outside
contractors) and those in management
on whose property cutting and welding
is to be performed, see Standard for
Fire Prevention in Use of Cutting and
Welding Processes, NFPA Standard
51B, 1962, which is incorporated by reference as specified in § 1910.6. The basic
precautions for fire prevention in welding or cutting work are:
(i) Fire hazards. If the object to be
welded or cut cannot readily be moved,
all movable fire hazards in the vicinity
shall be taken to a safe place.
(ii) Guards. If the object to be welded
or cut cannot be moved and if all the
fire hazards cannot be removed, then
guards shall be used to confine the
heat, sparks, and slag, and to protect
the immovable fire hazards.
(iii) Restrictions. If the requirements
stated in paragraphs (a)(1)(i) and
(a)(1)(ii) of this section cannot be followed then welding and cutting shall
not be performed.
(2) Special precautions. When the nature of the work to be performed falls
within the scope of paragraph (a)(1)(ii)
of this section certain additional precautions may be necessary:
(i) Combustible material. Wherever
there are floor openings or cracks in
the flooring that cannot be closed, precautions shall be taken so that no
readily combustible materials on the
floor below will be exposed to sparks
which might drop through the floor.
The same precautions shall be observed
with regard to cracks or holes in walls,
open doorways and open or broken windows.
(ii) Fire extinquishers. Suitable fire
extinguishing equipment shall be

maintained in a state of readiness for
instant use. Such equipment may consist of pails of water, buckets of sand,
hose or portable extinguishers depending upon the nature and quantity of
the combustible material exposed.
(iii) Fire watch. (A) Fire watchers
shall be required whenever welding or
cutting is performed in locations where
other than a minor fire might develop,
or any of the following conditions
exist:
(1) Appreciable combustible material,
in building construction or contents,
closer than 35 feet (10.7 m) to the point
of operation.
(2) Appreciable combustibles are
more than 35 feet (10.7 m) away but are
easily ignited by sparks.
(3) Wall or floor openings within a 35foot (10.7 m) radius expose combustible
material in adjacent areas including
concealed spaces in walls or floors.
(4) Combustible materials are adjacent to the opposite side of metal partitions, walls, ceilings, or roofs and are
likely to be ignited by conduction or
radiation.
(B) Fire watchers shall have fire extinguishing equipment readily available and be trained in its use. They
shall be familiar with facilities for
sounding an alarm in the event of a
fire. They shall watch for fires in all
exposed areas, try to extinguish them
only when obviously within the capacity of the equipment available, or otherwise sound the alarm. A fire watch
shall be maintained for at least a half
hour after completion of welding or
cutting operations to detect and extinguish possible smoldering fires.
(iv) Authorization. Before cutting or
welding is permitted, the area shall be
inspected by the individual responsible
for authorizing cutting and welding operations. He shall designate precautions to be followed in granting authorization to proceed preferably in the
form of a written permit.
(v) Floors. Where combustible materials such as paper clippings, wood
shavings, or textile fibers are on the
floor, the floor shall be swept clean for
a radius of 35 feet (10.7 m). Combustible
floors shall be kept wet, covered with
damp sand, or protected by fire-resistant shields. Where floors have been wet
down, personnel operating arc welding

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Occupational Safety and Health Admin., Labor
or cutting equipment shall be protected from possible shock.
(vi) Prohibited areas. Cutting or welding shall not be permitted in the following situations:
(A) In areas not authorized by management.
(B) In sprinklered buildings while
such protection is impaired.
(C) In the presence of explosive
atmospheres (mixtures of flammable
gases, vapors, liquids, or dusts with
air), or explosive atmospheres that
may develop inside uncleaned or improperly prepared tanks or equipment
which have previously contained such
materials, or that may develop in areas
with an accumulation of combustible
dusts.
(D) In areas near the storage of large
quantities of exposed, readily ignitible
materials such as bulk sulfur, baled
paper, or cotton.
(vii) Relocation of combustibles. Where
practicable, all combustibles shall be
relocated at least 35 feet (10.7 m) from
the work site. Where relocation is impracticable, combustibles shall be protected with flameproofed covers or otherwise shielded with metal or asbestos
guards or curtains.
(viii) Ducts. Ducts and conveyor systems that might carry sparks to distant combustibles shall be suitably
protected or shut down.
(ix) Combustible walls. Where cutting
or welding is done near walls, partitions, ceiling or roof of combustible
construction, fire-resistant shields or
guards shall be provided to prevent ignition.
(x) Noncombustible walls. If welding is
to be done on a metal wall, partition,
ceiling or roof, precautions shall be
taken to prevent ignition of combustibles on the other side, due to conduction or radiation, preferably by relocating combustibles. Where combustibles are not relocated, a fire watch on
the opposite side from the work shall
be provided.
(xi) Combustible cover. Welding shall
not be attempted on a metal partition,
wall, ceiling or roof having a combustible covering nor on walls or partitions of combustible sandwich-type
panel construction.
(xii) Pipes. Cutting or welding on
pipes or other metal in contact with

§ 1910.252

combustible walls, partitions, ceilings
or roofs shall not be undertaken if the
work is close enough to cause ignition
by conduction.
(xiii) Management. Management shall
recognize its responsibility for the safe
usage of cutting and welding equipment on its property and:
(A) Based on fire potentials of plant
facilities, establish areas for cutting
and welding, and establish procedures
for cutting and welding, in other areas.
(B) Designate an individual responsible for authorizing cutting and welding operations in areas not specifically
designed for such processes.
(C) Insist that cutters or welders and
their supervisors are suitably trained
in the safe operation of their equipment and the safe use of the process.
(D) Advise all contractors about
flammable materials or hazardous conditions of which they may not be
aware.
(xiv) Supervisor. The Supervisor:
(A) Shall be responsible for the safe
handling of the cutting or welding
equipment and the safe use of the cutting or welding process.
(B) Shall determine the combustible
materials and hazardous areas present
or likely to be present in the work location.
(C) Shall protect combustibles from
ignition by the following:
(1) Have the work moved to a location free from dangerous combustibles.
(2) If the work cannot be moved, have
the combustibles moved to a safe distance from the work or have the combustibles properly shielded against ignition.
(3) See that cutting and welding are
so scheduled that plant operations that
might expose combustibles to ignition
are not started during cutting or welding.
(D) Shall secure authorization for the
cutting or welding operations from the
designated management representative.
(E) Shall determine that the cutter
or welder secures his approval that
conditions are safe before going ahead.
(F) Shall determine that fire protection and extinguishing equipment are
properly located at the site.

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§ 1910.252

29 CFR Ch. XVII (7–1–05 Edition)

(G) Where fire watches are required,
he shall see that they are available at
the site.
(xv) Fire prevention precautions. Cutting or welding shall be permitted only
in areas that are or have been made
fire safe. When work cannot be moved
practically, as in most construction
work, the area shall be made safe by
removing combustibles or protecting
combustibles from ignition sources.
(3) Welding or cutting containers—(i)
Used containers. No welding, cutting, or
other hot work shall be performed on
used drums, barrels, tanks or other
containers until they have been
cleaned so thoroughly as to make absolutely certain that there are no flammable materials present or any substances such as greases, tars, acids, or
other materials which when subjected
to heat, might produce flammable or
toxic vapors. Any pipe lines or connections to the drum or vessel shall be disconnected or blanked.
(ii) Venting and purging. All hollow
spaces, cavities or containers shall be
vented to permit the escape of air or
gases before preheating, cutting or
welding. Purging with inert gas is recommended.
(4) Confined spaces—(i) Accidental contact. When arc welding is to be suspended for any substantial period of
time, such as during lunch or overnight, all electrodes shall be removed
from the holders and the holders carefully located so that accidental contact
cannot occur and the machine be disconnected from the power source.
(ii) Torch valve. In order to eliminate
the possibility of gas escaping through
leaks or improperly closed valves,
when gas welding or cutting, the torch
valves shall be closed and the gas supply to the torch positively shut off at
some point outside the confined area
whenever the torch is not to be used
for a substantial period of time, such
as during lunch hour or overnight.
Where practicable, the torch and hose
shall also be removed from the confined space.
(b) Protection of personnel—(1) General—(i) Railing. A welder or helper
working on platforms, scaffolds, or
runways shall be protected against falling. This may be accomplished by the
use of railings, safety belts, life lines,

or some other equally effective safeguards.
(ii) Welding cable. Welders shall place
welding cable and other equipment so
that it is clear of passageways, ladders,
and stairways.
(2) Eye protection—(i) Selection. (A)
Helmets or hand shields shall be used
during all arc welding or arc cutting
operations, excluding submerged arc
welding. Helpers or attendants shall be
provided with proper eye protection.
(B) Goggles or other suitable eye protection shall be used during all gas
welding or oxygen cutting operations.
Spectacles without side shields, with
suitable filter lenses are permitted for
use during gas welding operations on
light work, for torch brazing or for inspection.
(C) All operators and attendants of
resistance welding or resistance brazing equipment shall use transparent
face shields or goggles, depending on
the particular job, to protect their
faces or eyes, as required.
(D) Eye protection in the form of
suitable goggles shall be provided
where needed for brazing operations
not covered in paragraphs (b)(2)(i)(A)
through (b)(2)(i)(C) of this section.
(ii) Specifications for protectors. (A)
Helmets and hand shields shall be made
of a material which is an insulator for
heat and electricity. Helmets, shields
and goggles shall be not readily flammable and shall be capable of withstanding sterilization.
(B) Helmets and hand shields shall be
arranged to protect the face, neck and
ears from direct radiant energy from
the arc.
(C) Helmets shall be provided with
filter plates and cover plates designed
for easy removal.
(D) All parts shall be constructed of a
material which will not readily corrode
or discolor the skin.
(E) Goggles shall be ventilated to
prevent fogging of the lenses as much
as practicable.
(F) All glass for lenses shall be tempered, substantially free from striae,
air bubbles, waves and other flaws. Except when a lens is ground to provide
proper optical correction for defective
vision, the front and rear surfaces of
lenses and windows shall be smooth
and parallel.

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Occupational Safety and Health Admin., Labor
(G) Lenses shall bear some permanent distinctive marking by which the
source and shade may be readily identified.
(H) The following is a guide for the
selection of the proper shade numbers.
These recommendations may be varied
to suit the individual’s needs.
Shade
No.

Welding operation
Shielded metal-arc welding—1⁄16-, 3⁄32-, 1⁄8-, 5⁄32inch electrodes .......................................................
Gas-shielded arc welding (nonferrous)—1⁄16-, 3⁄32-,
1⁄8-, 5⁄32-inch electrodes .........................................
Gas-shielded arc welding (ferrous)—1⁄16-, 3⁄32-, 1⁄8-,
5⁄32-inch electrodes ................................................
Shielded metal-arc welding:
3⁄16-, 7⁄32-, 1⁄4-inch electrodes ......................
5⁄16-, 3⁄8-inch electrodes ..............................
Atomic hydrogen welding ..........................................
Carbon arc welding ...................................................
Soldering ....................................................................
Torch brazing .............................................................
Light cutting, up to 1 inch ..........................................
Medium cutting, 1 inch to 6 inches ...........................
Heavy cutting, 6 inches and over ..............................
Gas welding (light) up to 1⁄8 inch ..............................
Gas welding (medium) 1⁄8 inch to 1⁄2 inch .................
Gas welding (heavy) 1⁄2 inch and over .....................

10
11
12
12
14
10–14
14
2
3 or 4
3 or 4
4 or 5
5 or 6
4 or 5
5 or 6
6 or 8

Note: In gas welding or oxygen cutting where the torch produces a high yellow light, it is desirable to use a filter or lens
that absorbs the yellow or sodium line in the visible light of
the operation.

(I) All filter lenses and plates shall
meet the test for transmission of radiant energy prescribed in ANSI Z87.1—
1968—American
National
Standard
Practice for Occupational and Educational Eye and Face Protection,
which is incorporated by reference as
specified in § 1910.6.
(iii) Protection from arc welding rays.
Where the work permits, the welder
should be enclosed in an individual
booth painted with a finish of low reflectivity such as zinc oxide (an important factor for absorbing ultraviolet
radiations) and lamp black, or shall be
enclosed with noncombustible screens
similarly painted. Booths and screens
shall permit circulation of air at floor
level. Workers or other persons adjacent to the welding areas shall be protected from the rays by noncombustible or flameproof screens or shields
or shall be required to wear appropriate goggles.
(3) Protective clothing—General requirements. Employees exposed to the hazards created by welding, cutting, or
brazing operations shall be protected
by personal protective equipment in
accordance with the requirements of

§ 1910.252

§ 1910.132 of this part. Appropriate protective clothing required for any welding operation will vary with the size,
nature and location of the work to be
performed.
(4) Work in confined spaces—(i) General. As used herein confined space is
intended to mean a relatively small or
restricted space such as a tank, boiler,
pressure vessel, or small compartment
of a ship.
(ii) Ventilation. Ventilation is a prerequisite to work in confined spaces.
For ventilation requirements see paragraph (c) of this section.
(iii) Securing cylinders and machinery.
When welding or cutting is being performed in any confined spaces the gas
cylinders and welding machines shall
be left on the outside. Before operations are started, heavy portable
equipment mounted on wheels shall be
securely blocked to prevent accidental
movement.
(iv) Lifelines. Where a welder must
enter a confined space through a manhole or other small opening, means
shall be provided for quickly removing
him in case of emergency. When safety
belts and lifelines are used for this purpose they shall be so attached to the
welder’s body that his body cannot be
jammed in a small exit opening. An attendant with a preplanned rescue procedure shall be stationed outside to observe the welder at all times and be capable of putting rescue operations into
effect.
(v) Electrode removal. When arc welding is to be suspended for any substantial period of time, such as during
lunch or overnight, all electrodes shall
be removed from the holders and the
holders carefully located so that accidental contact cannot occur and the
machine disconnected from the power
source.
(vi) Gas cylinder shutoff. In order to
eliminate the possibility of gas escaping through leaks of improperly closed
valves, when gas welding or cutting,
the torch valves shall be closed and the
fuel-gas and oxygen supply to the torch
positively shut off at some point outside the confined area whenever the
torch is not to be used for a substantial
period of time, such as during lunch
hour or overnight. Where practicable

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§ 1910.252

29 CFR Ch. XVII (7–1–05 Edition)

the torch and hose shall also be removed from the confined space.
(vii) Warning sign. After welding operations are completed, the welder
shall mark the hot metal or provide
some other means of warning other
workers.
(c) Health protection and ventilation—
(1) General—(i) Contamination. The requirements in this paragraph have been
established on the basis of the following three factors in arc and gas
welding which govern the amount of
contamination to which welders may
be exposed:
(A) Dimensions of space in which
welding is to be done (with special regard to height of ceiling).
(B) Number of welders.
(C) Possible evolution of hazardous
fumes, gases, or dust according to the
metals involved.
(ii) Screens. When welding must be
performed in a space entirely screened
on all sides, the screens shall be so arranged that no serious restriction of
ventilation exists. It is desirable to
have the screens so mounted that they
are about 2 feet (0.61 m) above the floor
unless the work is performed at so low
a level that the screen must be extended nearer to the floor to protect
nearby workers from the glare of welding.
(iii) Maximum allowable concentration.
Local exhaust or general ventilating
systems shall be provided and arranged
to keep the amount of toxic fumes,
gases, or dusts below the maximum allowable concentration as specified in
§ 1910.1000 of this part.
(iv) Precautionary labels. A number of
potentially hazardous materials are
employed in fluxes, coatings, coverings, and filler metals used in welding and cutting or are released to the
atmosphere during welding and cutting. These include but are not limited
to the materials itemized in paragraphs (c)(5) through (c)(12) of this section. The suppliers of welding materials shall determine the hazard, if any,
associated with the use of their materials in welding, cutting, etc.
(A) All filler metals and fusible
granular materials shall carry the following notice, as a minimum, on tags,
boxes, or other containers:

CAUTION
Welding may produce fumes and gases hazardous to health. Avoid breathing these
fumes and gases. Use adequate ventilation.
See ANSI Z49.1 – 1967 Safety in Welding and
Cutting published by the American Welding
Society.

(B) Brazing (welding) filler metals
containing cadmium in significant
amounts shall carry the following notice on tags, boxes, or other containers:
WARNING
CONTAINS CADMIUM—POISONOUS
FUMES MAY BE FORMED ON HEATING
Do not breathe fumes. Use only with adequate ventilation such as fume collectors,
exhaust ventilators, or air-supplied respirators. See ANSI Z49.1 – 1967. If chest pain,
cough, or fever develops after use call physician immediately.

(C) Brazing and gas welding fluxes
containing fluorine compounds shall
have a cautionary wording to indicate
that they contain fluorine compounds.
One such cautionary wording recommended by the American Welding
Society for brazing and gas welding
fluxes reads as follows:
CAUTION
CONTAINS FLUORIDES
This flux when heated gives off fumes that
may irritate eyes, nose and throat.
1. Avoid fumes—use only in well-ventilated
spaces.
2. Avoid contact of flux with eyes or skin.
3. Do not take internally.

(2) Ventilation for general welding and
cutting—(i) General. Mechanical ventilation shall be provided when welding
or cutting is done on metals not covered in paragraphs (c)(5) through (c)(12)
of this section. (For specific materials,
see the ventilation requirements of
paragraphs (c)(5) through (c)(12) of this
section.)
(A) In a space of less than 10,000 cubic
feet (284 m 3) per welder.
(B) In a room having a ceiling height
of less than 16 feet (5 m).
(C) In confined spaces or where the
welding space contains partitions, balconies, or other structural barriers to
the extent that they significantly obstruct cross ventilation.
(ii) Minimum rate. Such ventilation
shall be at the minimum rate of 2,000

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Occupational Safety and Health Admin., Labor
cubic feet (57 m3) per minute per welder, except where local exhaust hoods
and booths as per paragraph (c)(3) of
this section, or airline respirators approved by the Mine Safety and Health
Administration and the National Institute for Occupational Safety and
Health, pursuant to the provisions of 30
CFR part 11, are provided. Natural ventilation is considered sufficient for
welding or cutting operations where
the restrictions in paragraph (c)(2)(i) of
this section are not present.
(3) Local exhaust hoods and booths.
Mechanical local exhaust ventilation
may be by means of either of the following:
(i) Hoods. Freely movable hoods intended to be placed by the welder as
near as practicable to the work being
welded and provided with a rate of airflow sufficient to maintain a velocity
in the direction of the hood of 100 linear feet (30 m) per minute in the zone
of welding when the hood is at its most
remote distance from the point of
welding. The rates of ventilation required to accomplish this control velocity using a 3-inch (7.6 cm) wide
flanged suction opening are shown in
the following table:
Welding zone

Minimum air
flow 1 cubic
feet/minute

Duct diameter, inches 2

150
275
425

3
31⁄2
41⁄2

600

51⁄2

4 to 6 inches from arc or torch
6 to 8 inches from arc or torch
8 to 10 inches from arc or torch
10 to 12 inches from arc or
torch .......................................
1 When

brazing with cadmium bearing materials or when
cutting on such materials increased rates of ventilation may
be required.
2 Nearest half-inch duct diameter based on 4,000 feet per
minute velocity in pipe.

(ii) Fixed enclosure. A fixed enclosure
with a top and not less than two sides
which surround the welding or cutting
operations and with a rate of airflow
sufficient to maintain a velocity away
from the welder of not less than 100 linear feet (30 m) per minute.
(4) Ventilation in confined spaces—(i)
Air replacement. All welding and cutting
operations carried on in confined
spaces shall be adequately ventilated
to prevent the accumulation of toxic
materials or possible oxygen deficiency. This applies not only to the
welder but also to helpers and other
personnel in the immediate vicinity.

§ 1910.252

All air replacing that withdrawn shall
be clean and respirable.
(ii)
Airline
respirators.
In
circumstances for which it is impossible
to provide such ventilation, airline respirators or hose masks approved for
this purpose by the National Institute
for Occupational Safety and Health
(NIOSH) under 42 CFR part 84 must be
used.
(iii) Self-contained units. In areas immediately hazardous to life, a full-facepiece, pressure-demand, self-contained
breathing apparatus or a combination
full-facepiece, pressure-demand supplied-air respirator with an auxiliary,
self-contained air supply approved by
NIOSH under 42 CFR part 84 must be
used.
(iv) Outside helper. Where welding operations are carried on in confined
spaces and where welders and helpers
are provided with hose masks, hose
masks with blowers or self-contained
breathing equipment approved by the
Mine Safety and Health Administration and the National Institute for Occupational Safety and Health, a worker
shall be stationed on the outside of
such confined spaces to insure the safety of those working within.
(v) Oxygen for ventilation. Oxygen
shall never be used for ventilation.
(5) Fluorine compounds—(i) General. In
confined spaces, welding or cutting involving fluxes, coverings, or other materials which contain fluorine compounds shall be done in accordance
with paragraph (c)(4) of this section. A
fluorine compound is one that contains
fluorine, as an element in chemical
combination, not as a free gas.
(ii) Maximum allowable concentration.
The need for local exhaust ventilation
or airline respirators for welding or
cutting in other than confined spaces
will depend upon the individual circumstances. However, experience has
shown such protection to be desirable
for fixed-location production welding
and for all production welding on stainless steels. Where air samples taken at
the welding location indicate that the
fluorides liberated are below the maximum allowable concentration, such
protection is not necessary.
(6) Zinc—(i) Confined spaces. In confined spaces welding or cutting involving zinc-bearing base or filler metals or

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§ 1910.252

29 CFR Ch. XVII (7–1–05 Edition)

metals coated with zinc-bearing materials shall be done in accordance with
paragraph (c)(4) of this section.
(ii) Indoors. Indoors, welding or cutting involving zinc-bearing base or
filler metals coated with zinc-bearing
materials shall be done in accordance
with paragraph (c)(3) of this section.
(7) Lead—(i) Confined spaces. In confined spaces, welding involving leadbase metals (erroneously called leadburning) shall be done in accordance
with paragraph (c)(4) of this section.
(ii) Indoors. Indoors, welding involving lead-base metals shall be done in
accordance with paragraph (c)(3) of this
section.
(iii) Local ventilation. In confined
spaces or indoors, welding or cutting
operations involving metals containing
lead, other than as an impurity, or
metals coated with lead-bearing materials, including paint, must be done
using local exhaust ventilation or airline respirators. Such operations, when
done outdoors, must be done using respirators approved for this purpose by
NIOSH under 42 CFR part 84. In all
cases, workers in the immediate vicinity of the cutting operation must be
protected by local exhaust ventilation
or airline respirators.
(8) Beryllium. Welding or cutting indoors, outdoors, or in confined spaces
involving beryllium-containing base or
filler metals shall be done using local
exhaust ventilation and airline respirators unless atmospheric tests under
the most adverse conditions have established that the workers’ exposure is
within the acceptable concentrations
defined by § 1910.1000 of this part. In all
cases, workers in the immediate vicinity of the welding or cutting operations
shall be protected as necessary by local
exhaust ventilation or airline respirators.
(9) Cadmium—(i) General. In confined
spaces or indoors, welding or cutting
operations involving cadmium-bearing
or cadmium-coated base metals must
be done using local exhaust ventilation
or airline respirators unless atmospheric tests under the most adverse
conditions show that employee exposure is within the acceptable concentrations specified by 29 CFR
1910.1000. Such operations, when done
outdoors, must be done using res-

pirators, such as fume respirators, approved for this purpose by NIOSH
under 42 CFR part 84.
(ii) Confined space. Welding (brazing)
involving cadmium-bearing filler metals shall be done using ventilation as
prescribed in paragraph (c)(3) or (c)(4)
of this section if the work is to be done
in a confined space.
(10) Mercury. In confined spaces or indoors, welding or cutting operations involving metals coated with mercurybearing materials, including paint,
must be done using local exhaust ventilation or airline respirators unless atmospheric tests under the most adverse
conditions show that employee exposure is within the acceptable concentrations specified by 29 CFR
1910.1000. Such operations, when done
outdoors, must be done using respirators approved for this purpose by
NIOSH under 42 CFR part 84.
(11) Cleaning compounds—(i) Manufacturer’s instructions. In the use of cleaning materials, because of their possible
toxicity or flammability, appropriate
precautions such as manufacturers instructions shall be followed.
(ii) Degreasing. Degreasing and other
cleaning
operations
involving
chlorinated hydrocarbons shall be so
located that no vapors from these operations will reach or be drawn into the
atmosphere surrounding any welding
operation.
In
addition,
trichloroethylene and perchlorethylene should
be kept out of atmospheres penetrated
by the ultraviolet radiation of gasshielded welding operations.
(12) Cutting of stainless steels. Oxygen
cutting, using either a chemical flux or
iron powder or gas-shielded arc cutting
of stainless steel, shall be done using
mechanical ventilation adequate to remove the fumes generated.
(13) First-aid equipment. First-aid
equipment shall be available at all
times. All injuries shall be reported as
soon as possible for medical attention.
First aid shall be rendered until medical attention can be provided.
(d) Industrial applications—(1) Transmission pipeline—(i) General. The requirements of paragraphs (b) and (c) of
this section and § 1910.254 of this part
shall be observed.

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Occupational Safety and Health Admin., Labor
(ii) Field shop operations. Where field
shop operations are involved for fabrication of fittings, river crossings,
road crossings, and pumping and compressor stations the requirements of
paragraphs (a), (b), and (c) of this section and §§ 1910.253 and 1910.254 of this
part shall be observed.
(iii) Electric shock. When arc welding
is performed in wet conditions, or
under conditions of high humidity, special protection against electric shock
shall be supplied.
(iv) Pressure testing. In pressure testing of pipelines, the workers and the
public shall be protected against injury
by the blowing out of closures or other
pressure restraining devices. Also, protection shall be provided against expulsion of loose dirt that may have become trapped in the pipe.
(v) Construction standards. The welded
construction of transmission pipelines
shall be conducted in accordance with
the Standard for Welding Pipe Lines
and Related Facilities, API Std. 1104—
1968, which is incorporated by reference
as specified in § 1910.6.
(vi) Flammable substance lines. The
connection, by welding, of branches to
pipelines carrying flammable substances shall be performed in accordance with Welding or Hot Tapping on
Equipment Containing Flammables,
API Std. PSD No. 2201—1963, which is
incorporated by reference as specified
in § 1910.6.
(vii) X-ray inspection. The use of Xrays and radioactive isotopes for the
inspection of welded pipeline joints
shall be carried out in conformance
with the American National Standard
Safety Standard for Non-Medical X-ray
and Sealed Gamma-Ray Sources, ANSI
Z54.1—1963, which is incorporated by
reference as specified in § 1910.6.
(2) Mechanical piping systems—(i) General. The requirements of paragraphs
(a), (b), and (c) of this section and
§§ 1910.253 and 1910.254 of this part shall
be observed.
(ii) X-ray inspection. The use of Xrays and radioactive isotopes for the
inspection of welded piping joints shall
be in conformance with the American
National Standard Safety Standard for

§ 1910.253

Non-Medical X-ray and Sealed GammaRay Sources, ANSI Z54.1—1963.
[55 FR 13696, Apr. 11, 1990, as amended at 61
FR 9240, Mar. 7, 1996; 63 FR 1284, Jan. 8, 1998]

§ 1910.253 Oxygen-fuel gas welding
and cutting.
(a) General requirements—(1) Flammable mixture. Mixtures of fuel gases
and air or oxygen may be explosive and
shall be guarded against. No device or
attachment facilitating or permitting
mixtures of air or oxygen with flammable gases prior to consumption, except at the burner or in a standard
torch, shall be allowed unless approved
for the purpose.
(2) Maximum pressure. Under no condition shall acetylene be generated,
piped (except in approved cylinder
manifolds) or utilized at a pressure in
excess of 15 psig (103 kPa gauge pressure) or 30 psia (206 kPa absolute). The
30 psia (206 kPa absolute) limit is intended to prevent unsafe use of
acetylene in pressurized chambers such
as caissons, underground excavations
or tunnel construction.) This requirement is not intended to apply to storage of acetylene dissolved in a suitable
solvent in cylinders manufactured and
maintained according to U.S. Department of Transportation requirements,
or to acetylene for chemical use. The
use of liquid acetylene shall be prohibited.
(3) Apparatus. Only approved apparatus such as torches, regulators or
pressure-reducing valves, acetylene
generators, and manifolds shall be
used.
(4) Personnel. Workmen in charge of
the oxygen or fuel-gas supply equipment, including generators, and oxygen
or fuel-gas distribution piping systems
shall be instructed and judged competent by their employers for this important work before being left in
charge. Rules and instructions covering the operation and maintenance of
oxygen or fuel-gas supply equipment
including generators, and oxygen or
fuel-gas distribution piping systems
shall be readily available.
(b) Cylinders and containers—(1) Approval and marking. (i) All portable cylinders used for the storage and shipment of compressed gases shall be constructed and maintained in accordance

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§ 1910.253

29 CFR Ch. XVII (7–1–05 Edition)

with the regulations of the U.S. Department of Transportation, 49 CFR
parts 171–179.
(ii) Compressed gas cylinders shall be
legibly marked, for the purpose of identifying the gas content, with either the
chemical or the trade name of the gas.
Such marking shall be by means of
stenciling, stamping, or labeling, and
shall not be readily removable. Whenever practical, the marking shall be located on the shoulder of the cylinder.
This method conforms to the American
National Standard Method for Marking
Portable Compressed Gas Containers to
Identify the Material Contained, ANSI
Z48.1—1954, which is incorporated by
reference as specified in § 1910.6.
(iii) Compressed gas cylinders shall
be equipped with connections complying with the American National
Standard Compressed Gas Cylinder
Valve Outlet and Inlet Connections,
ANSI B57.1—1965, which is incorporated
by reference as specified in § 1910.6.
(iv) All cylinders with a water weight
capacity of over 30 pounds (13.6 kg)
shall be equipped with means of connecting a valve protection cap or with
a collar or recess to protect the valve.
(2) Storage of cylinders—general. (i)
Cylinders shall be kept away from radiators and other sources of heat.
(ii) Inside of buildings, cylinders
shall be stored in a well-protected,
well-ventilated, dry location, at least
20 feet (6.1 m) from highly combustible
materials such as oil or excelsior. Cylinders should be stored in definitely assigned places away from elevators,
stairs, or gangways. Assigned storage
spaces shall be located where cylinders
will not be knocked over or damaged
by passing or falling objects, or subject
to tampering by unauthorized persons.
Cylinders shall not be kept in
unventilated enclosures such as lockers
and cupboards.
(iii) Empty cylinders shall have their
valves closed.
(iv) Valve protection caps, where cylinder is designed to accept a cap, shall
always be in place, hand-tight, except
when cylinders are in use or connected
for use.
(3) Fuel-gas cylinder storage. Inside a
building, cylinders, except those in actual use or attached ready for use,
shall be limited to a total gas capacity

of 2,000 cubic feet (56 m3) or 300 pounds
(135.9 kg) of liquefied petroleum gas.
(i) For storage in excess of 2,000 cubic
feet (56 m3) total gas capacity of cylinders or 300 (135.9 kg) pounds of liquefied petroleum gas, a separate room or
compartment conforming to the requirements specified in paragraphs
(f)(6)(i)(H) and (f)(6)(i)(I) of this section
shall be provided, or cylinders shall be
kept outside or in a special building.
Special buildings, rooms or compartments shall have no open flame for
heating or lighting and shall be well
ventilated. They may also be used for
storage of calcium carbide in quantities not to exceed 600 (271.8 kg)
pounds, when contained in metal containers complying with paragraphs
(g)(1)(i) and (g)(1)(ii) of this section.
(ii) Acetylene cylinders shall be
stored valve end up.
(4) Oxygen storage. (i) Oxygen cylinders shall not be stored near highly
combustible material, especially oil
and grease; or near reserve stocks of
carbide and acetylene or other fuel-gas
cylinders, or near any other substance
likely to cause or accelerate fire; or in
an acetylene generator compartment.
(ii) Oxygen cylinders stored in outside generator houses shall be separated from the generator or carbide
storage rooms by a noncombustible
partition having a fire-resistance rating of at least 1 hour. This partition
shall be without openings and shall be
gastight.
(iii) Oxygen cylinders in storage shall
be separated from fuel-gas cylinders or
combustible materials (especially oil
or grease), a minimum distance of 20
feet (6.1 m) or by a noncombustible barrier at least 5 feet (1.5 m) high having
a fire-resistance rating of at least onehalf hour.
(iv) Where a liquid oxygen system is
to be used to supply gaseous oxygen for
welding or cutting and the system has
a storage capacity of more than 13,000
cubic feet (364 m3) of oxygen (measured
at 14.7 psia (101 kPa) and 70 °F (21.1
°C)), connected in service or ready for
service, or more than 25,000 cubic feet
(700 m3) of oxygen (measured at 14.7
psia (101 kPa) and 70 °F (21.1 °C)), including unconnected reserves on hand
at the site, it shall comply with the

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Occupational Safety and Health Admin., Labor
provisions of the Standard for Bulk Oxygen Systems at Consumer Sites,
NFPA No. 566—1965, which is incorporated by reference as specified in
§ 1910.6.
(5) Operating procedures. (i) Cylinders,
cylinder valves, couplings, regulators,
hose, and apparatus shall be kept free
from oily or greasy substances. Oxygen
cylinders or apparatus shall not be
handled with oily hands or gloves. A
jet of oxygen must never be permitted
to strike an oily surface, greasy
clothes, or enter a fuel oil or other
storage tank.
(ii)(A) When transporting cylinders
by a crane or derrick, a cradle, boat, or
suitable platform shall be used. Slings
or electric magnets shall not be used
for this purpose. Valve-protection caps,
where cylinder is designed to accept a
cap, shall always be in place.
(B) Cylinders shall not be dropped or
struck or permitted to strike each
other violently.
(C) Valve-protection caps shall not be
used for lifting cylinders from one
vertical position to another. Bars shall
not be used under valves or valve-protection caps to pry cylinders loose
when frozen to the ground or otherwise
fixed; the use of warm (not boiling)
water is recommended. Valve-protection caps are designed to protect cylinder valves from damage.
(D) Unless cylinders are secured on a
special truck, regulators shall be removed and valve-protection caps, when
provided for, shall be put in place before cylinders are moved.
(E) Cylinders not having fixed hand
wheels shall have keys, handles, or
nonadjustable wrenches on valve stems
while these cylinders are in service. In
multiple cylinder installations only
one key or handle is required for each
manifold.
(F) Cylinder valves shall be closed before moving cylinders.
(G) Cylinder valves shall be closed
when work is finished.
(H) Valves of empty cylinders shall
be closed.
(I) Cylinders shall be kept far enough
away from the actual welding or cutting operation so that sparks, hot slag,
or flame will not reach them, or fireresistant shields shall be provided.

§ 1910.253

(J) Cylinders shall not be placed
where they might become part of an
electric circuit. Contacts with third
rails, trolley wires, etc., shall be avoided. Cylinders shall be kept away from
radiators, piping systems, layout tables, etc., that may be used for grounding electric circuits such as for arc
welding machines. Any practice such
as the tapping of an electrode against a
cylinder to strike an arc shall be prohibited.
(K) Cylinders shall never be used as
rollers or supports, whether full or
empty.
(L) The numbers and markings
stamped into cylinders shall not be
tampered with.
(M) No person, other than the gas
supplier, shall attempt to mix gases in
a cylinder. No one, except the owner of
the cylinder or person authorized by
him, shall refill a cylinder.
(N) No one shall tamper with safety
devices in cylinders or valves.
(O) Cylinders shall not be dropped or
otherwise roughly handled.
(P) Unless connected to a manifold,
oxygen from a cylinder shall not be
used without first attaching an oxygen
regulator to the cylinder valve. Before
connecting the regulator to the cylinder valve, the valve shall be opened
slightly for an instant and then closed.
Always stand to one side of the outlet
when opening the cylinder valve.
(Q) A hammer or wrench shall not be
used to open cylinder valves. If valves
cannot be opened by hand, the supplier
shall be notified.
(R)(1) Cylinder valves shall not be
tampered with nor should any attempt
be made to repair them. If trouble is
experienced, the supplier should be
sent a report promptly indicating the
character of the trouble and the cylinder’s serial number. Supplier’s instructions as to its disposition shall be
followed.
(2) Complete removal of the stem
from a diaphragm-type cylinder valve
shall be avoided.
(iii)(A) Fuel-gas cylinders shall be
placed with valve end up whenever
they are in use. Liquefied gases shall
be stored and shipped with the valve
end up.
(B) Cylinders shall be handled carefully. Rough handling, knocks, or falls

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§ 1910.253

29 CFR Ch. XVII (7–1–05 Edition)

are liable to damage the cylinder,
valve or safety devices and cause leakage.
(C) Before connecting a regulator to
a cylinder valve, the valve shall be
opened slightly and closed immediately. The valve shall be opened
while standing to one side of the outlet; never in front of it. Never crack a
fuel-gas cylinder valve near other welding work or near sparks, flame, or
other possible sources of ignition.
(D) Before a regulator is removed
from a cylinder valve, the cylinder
valve shall be closed and the gas released from the regulator.
(E) Nothing shall be placed on top of
an acetylene cylinder when in use
which may damage the safety device or
interfere with the quick closing of the
valve.
(F) If cylinders are found to have
leaky valves or fittings which cannot
be stopped by closing of the valve, the
cylinders shall be taken outdoors away
from sources of ignition and slowly
emptied.
(G) A warning should be placed near
cylinders having leaking fuse plugs or
other leaking safety devices not to approach them with a lighted cigarette or
other source of ignition. Such cylinders
should be plainly tagged; the supplier
should be promptly notified and his instructions followed as to their return.
(H) Safety devices shall not be tampered with.
(I) Fuel-gas shall never be used from
cylinders through torches or other devices equipped with shutoff valves
without reducing the pressure through
a suitable regulator attached to the
cylinder valve or manifold.
(J) The cylinder valve shall always be
opened slowly.
(K) An acetylene cylinder valve shall
not be opened more than one and onehalf turns of the spindle, and preferably no more than three-fourths of a
turn.
(L) Where a special wrench is required it shall be left in position on the
stem of the valve while the cylinder is
in use so that the fuel-gas flow can be
quickly turned off in case of emergency. In the case of manifolded or
coupled cylinders at least one such
wrench shall always be available for
immediate use.

(c) Manifolding of cylinders—(1) Fuelgas manifolds. (i) Manifolds shall be approved either separately for each component part or as an assembled unit.
(ii) Except as provided in paragraph
(c)(1)(iii) of this section fuel-gas cylinders connected to one manifold inside a building shall be limited to a
total capacity not exceeding 300 pounds
(135.9 kg) of liquefied petroleum gas or
3,000 cubic feet (84 m 3) of other fuelgas. More than one such manifold with
connected cylinders may be located in
the same room provided the manifolds
are at least 50 feet (15 m) apart or separated by a noncombustible barrier at
least 5 feet (1.5 m) high having a fireresistance rating of at least one-half
hour.
(iii) Fuel-gas cylinders connected to
one manifold having an aggregate capacity exceeding 300 pounds (135.9 kg)
of liquefied petroleum gas or 3,000
cubic feet (84 m 3) of other fuel-gas
shall be located outdoors, or in a separate building or room constructed in
accordance with paragraphs (f)(6)(i)(H)
and (f)(6)(i)(I) of this section.
(iv) Separate manifold buildings or
rooms may also be used for the storage
of drums of calcium carbide and cylinders containing fuel gases as provided in paragraph (b)(3) of this section. Such buildings or rooms shall
have no open flames for heating or
lighting and shall be well-ventilated.
(v) High-pressure fuel-gas manifolds
shall be provided with approved pressure regulating devices.
(2) High-pressure oxygen manifolds (for
use with cylinders having a Department
of Transportation service pressure above
200 psig (1.36 MPa)). (i) Manifolds shall
be approved either separately for each
component part or as an assembled
unit.
(ii) Oxygen manifolds shall not be located in an acetylene generator room.
Oxygen manifolds shall be separated
from fuel-gas cylinders or combustible
materials (especially oil or grease), a
minimum distance of 20 feet (6.1 m) or
by a noncombustible barrier at least 5
feet (1.5 m) high having a fire-resistance rating of at least one-half hour.
(iii) Except as provided in paragraph
(c)(2)(iv) of this section, oxygen cylinders connected to one manifold shall
be limited to a total gas capacity of

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Occupational Safety and Health Admin., Labor
6,000 cubic feet (168 m 3). More than one
such manifold with connected cylinders
may be located in the same room provided the manifolds are at least 50 feet
(15 m) apart or separated by a noncombustible barrier at least 5 feet (1.5
m) high having a fire-resistance rating
of at least one-half hour.
(iv) An oxygen manifold, to which
cylinders having an aggregate capacity
of more than 6,000 cubic feet (168 m 3) of
oxygen are connected, should be located outdoors or in a separate noncombustible building. Such a manifold,
if located inside a building having
other occupancy, shall be located in a
separate room of noncombustible construction having a fire-resistance rating of at least one-half hour or in an
area with no combustible material
within 20 feet (6.1 m) of the manifold.
(v) An oxygen manifold or oxygen
bulk supply system which has storage
capacity of more than 13,000 cubic feet
(364 m 3) of oxygen (measured at 14.7
psia (101 kPa) and 70 °F (21.1 °C)), connected in service or ready for service,
or more than 25,000 cubic feet (700 m 3)
of oxygen (measured at 14.7 psia (101
kPa) and 70 °F (21.1 °C)), including
unconnected reserves on hand at the
site, shall comply with the provisions
of the Standard for Bulk Oxygen Systems at Consumer Sites, NFPA No. 566–
1965.
(vi) High-pressure oxygen manifolds
shall be provided with approved pressure-regulating devices.
(3) Low-pressure oxygen manifolds (for
use with cylinders having a Department
of Transportation service pressure not exceeding 200 psig (1.36 MPa)). (i) Manifolds shall be of substantial construction suitable for use with oxygen at a
pressure of 250 psig (1.7 MPa). They
shall have a minimum bursting pressure of 1,000 psig (6.8 MPa) and shall be
protected by a safety relief device
which will relieve at a maximum pressure of 500 psig (3.4 MPa). DOT–4L200
cylinders have safety devices which relieve at a maximum pressure of 250 psig
(1.7 MPa) (or 235 psig (1.6 MPa) if vacuum insulation is used).
(ii) Hose and hose connections subject to cylinder pressure shall comply
with paragraph (e)(5) of this section.
Hose shall have a minimum bursting
pressure of 1,000 psig (6.8 MPa).

§ 1910.253

(iii) The assembled manifold including leads shall be tested and proven
gas-tight at a pressure of 300 psig (2.04
MPa). The fluid used for testing oxygen
manifolds shall be oil-free and not
combustible.
(iv) The location of manifolds shall
comply with paragraphs (c)(2)(ii),
(c)(2)(iii), (c)(2)(iv), and (c)(2)(v) of this
section.
(v) The following sign shall be conspicuously posted at each manifold:
Low-Pressure Manifold
Do Not Connect High-Pressure Cylinders
Maximum Pressure—250 psig (1.7 MPa)

(4) Portable outlet headers. (i) Portable
outlet headers shall not be used indoors except for temporary service
where the conditions preclude a direct
supply from outlets located on the
service piping system.
(ii) Each outlet on the service piping
from which oxygen or fuel-gas is withdrawn to supply a portable outlet header shall be equipped with a readily accessible shutoff valve.
(iii) Hose and hose connections used
for connecting the portable outlet
header to the service piping shall comply with paragraph (e)(5) of this section.
(iv) Master shutoff valves for both
oxygen and fuel-gas shall be provided
at the entry end of the portable outlet
header.
(v) Portable outlet headers for fuelgas service shall be provided with an
approved hydraulic back-pressure valve
installed at the inlet and preceding the
service outlets, unless an approved
pressure-reducing regulator, an approved back-flow check valve, or an approved hydraulic back-pressure valve is
installed at each outlet. Outlets provided on headers for oxygen service
may be fitted for use with pressure-reducing regulators or for direct hose
connection.
(vi) Each service outlet on portable
outlet headers shall be provided with a
valve assembly that includes a detachable outlet seal cap, chained or otherwise attached to the body of the valve.
(vii) Materials and fabrication procedures for portable outlet headers shall
comply with paragraphs (d)(1), (d)(2),
and (d)(5) of this section.

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§ 1910.253

29 CFR Ch. XVII (7–1–05 Edition)

(viii) Portable outlet headers shall be
provided with frames which will support the equipment securely in the correct operating position and protect
them from damage during handling and
operation.
(5) Manifold operation procedures. (i)
Cylinder manifolds shall be installed
under the supervision of someone familiar with the proper practices with
reference to their construction and use.
(ii) All manifolds and parts used in
methods of manifolding shall be used
only for the gas or gases for which they
are approved.
(iii) When acetylene cylinders are
coupled, approved flash arresters shall
be installed between each cylinder and
the coupler block. For outdoor use
only, and when the number of cylinders
coupled does not exceed three, one
flash arrester installed between the
coupler block and regulator is acceptable.
(iv) The aggregate capacity of fuelgas cylinders connected to a portable
manifold inside a building shall not exceed 3,000 cubic feet (84 m 3) of gas.
(v) Acetylene and liquefied fuel-gas
cylinders shall be manifolded in a
vertical position.
(vi) The pressure in the gas cylinders
connected to and discharged simultaneously through a common manifold
shall be approximately equal.
(d) Service piping systems—(1) Materials
and design. (i)(A) Piping and fittings
shall comply with section 2, Industrial
Gas and Air Piping Systems, of the
American National Standard Code for
Pressure Piping ANSI B31.1, 1967, which
is incorporated by reference as specified in § 1910.6, insofar as it does not
conflict with paragraphs (d)(1)(i)(A)(1)
and (d)(1)(i)(A)(2) of this section:
(1) Pipe shall be at least Schedule 40
and fittings shall be at least standard
weight in sizes up to and including 6inch nominal.
(2) Copper tubing shall be Types K or
L in accordance with the Standard
Specification for Seamless Copper
Water Tube, ASTM B88–66a, which is
incorporated by reference as specified
in § 1910.6.
(B) Piping shall be steel, wrought
iron, brass or copper pipe, or seamless
copper, brass or stainless steel tubing,

except as provided in paragraphs
(d)(1)(ii) and (d)(1)(iii) of this section.
(ii)(A) Oxygen piping and fittings at
pressures in excess of 700 psi (4.8 MPa),
shall be stainless steel or copper alloys.
(B) Hose connections and hose complying with paragraph (e)(5) of this section may be used to connect the outlet
of a manifold pressure regulator to piping providing the working pressure of
the piping is 250 psi (1.7 MPa) or less
and the length of the hose does not exceed 5 feet (1.5 m). Hose shall have a
minimum bursting pressure of 1,000
psig (6.8 MPa).
(C) When oxygen is supplied to a
service piping system from a low-pressure oxygen manifold without an intervening pressure regulating device, the
piping system shall have a minimum
design pressure of 250 psig (1.7 MPa). A
pressure regulating device shall be used
at each station outlet when the connected equipment is for use at pressures less than 250 psig (1.7 MPa).
(iii)(A) Piping for acetylene or
acetylenic compounds shall be steel or
wrought iron.
(B) Unalloyed copper shall not be
used for acetylene or acetylenic compounds except in listed equipment.
(2) Piping joints. (i) Joints in steel or
wrought iron piping shall be welded,
threaded or flanged. Fittings, such as
ells, tees, couplings, and unions, may
be rolled, forged or cast steel, malleable iron or nodular iron. Gray or
white cast iron fittings are prohibited.
(ii) Joints in brass or copper pipe
shall be welded, brazed, threaded, or
flanged. If of the socket type, they
shall be brazed with silver-brazing
alloy or similar high melting point
(not less than 800 °F (427 °C)) filler
metal.
(iii) Joints in seamless copper, brass,
or stainless steel tubing shall be approved gas tubing fittings or the joints
shall be brazed. If of the socket type,
they shall be brazed with silver-brazing
alloy or similar high melting point
(not less than 800 °F (427 °C)) filler
metal.
(3) Installation. (i) Distribution lines
shall be installed and maintained in a
safe operating condition.
(ii) All piping shall be run as directly
as practicable, protected against physical damage, proper allowance being

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Occupational Safety and Health Admin., Labor
made for expansion and contraction,
jarring and vibration. Pipe laid underground in earth shall be located below
the frost line and protected against
corrosion. After assembly, piping shall
be thoroughly blown out with air, nitrogen, or carbon dioxide to remove
foreign materials. For oxygen piping,
only oil-free air, oil-free nitrogen, or
oil-free carbon dioxide shall be used.
(iii) Only piping which has been welded or brazed shall be installed in tunnels, trenches or ducts. Shutoff valves
shall be located outside such conduits.
Oxygen piping may be placed in the
same tunnel, trench or duct with fuelgas pipelines, provided there is good
natural or forced ventilation.
(iv) Low points in piping carrying
moist gas shall be drained into drip
pots constructed so as to permit pumping or draining out the condensate at
necessary intervals. Drain valves shall
be installed for this purpose having
outlets normally closed with screw
caps or plugs. No open end valves or
petcocks shall be used, except that in
drips located out of doors, underground, and not readily accessible,
valves may be used at such points if
they are equipped with means to secure
them in the closed position. Pipes leading to the surface of the ground shall
be cased or jacketed where necessary
to prevent loosening or breaking.
(v) Gas cocks or valves shall be provided for all buildings at points where
they will be readily accessible for shutting off the gas supply to these buildings in any emergency. There shall also
be provided a shutoff valve in the discharge line from the generator, gas
holder, manifold or other source of supply.
(vi) Shutoff valves shall not be installed in safety relief lines in such a
manner that the safety relief device
can be rendered ineffective.
(vii) Fittings and lengths of pipe
shall be examined internally before assembly and, if necessary freed from
scale or dirt. Oxygen piping and fittings shall be washed out with a suitable solution which will effectively remove grease and dirt but will not react
with oxygen. Hot water solutions of
caustic soda or trisodium phosphate
are effective cleaning agents for this
purpose.

§ 1910.253

(viii) Piping shall be thoroughly
blown out after assembly to remove
foreign materials. For oxygen piping,
oil-free air, oil-free nitrogen, or oil-free
carbon dioxide shall be used. For other
piping, air or inert gas may be used.
(ix) When flammable gas lines or
other parts of equipment are being
purged of air or gas, open lights or
other sources of ignition shall not be
permitted near uncapped openings.
(x) No welding or cutting shall be
performed on an acetylene or oxygen
pipeline, including the attachment of
hangers or supports, until the line has
been purged. Only oil-free air, oil-free
nitrogen, or oil-free carbon dioxide
shall be used to purge oxygen lines.
(4) Painting and signs. (i) Underground
pipe and tubing and outdoor ferrous
pipe and tubing shall be covered or
painted with a suitable material for
protection against corrosion.
(ii) Aboveground piping systems shall
be marked in accordance with the
American National Standard Scheme
for the Identification of Piping Systems, ANSI A13.1¥1956, which is incorporated by reference as specified in
§ 1910.6.
(iii) Station outlets shall be marked
to indicate the name of the gas.
(5) Testing. (i) Piping systems shall be
tested and proved gastight at 11⁄2 times
the maximum operating pressure, and
shall be thoroughly purged of air before
being placed in service. The material
used for testing oxygen lines shall be
oil free and noncombustible. Flames
shall not be used to detect leaks.
(ii) When flammable gas lines or
other parts of equipment are being
purged of air or gas, sources of ignition
shall not be permitted near uncapped
openings.
(e) Protective equipment, hose, and regulators—(1) General. Equipment shall be
installed and used only in the service
for which it is approved and as recommended by the manufacturer.
(2) Pressure relief devices. Service piping systems shall be protected by pressure relief devices set to function at
not more than the design pressure of
the systems and discharging upwards
to a safe location.
(3) Piping protective equipment. (i) The
fuel-gas and oxygen piping systems, including portable outlet headers shall

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§ 1910.253

29 CFR Ch. XVII (7–1–05 Edition)

incorporate the protective equipment
shown in Figures Q–1, Q–2, and Q–3.
When only a portion of a fuel-gas sys-

tem is to be used with oxygen, only
that portion need comply with this
paragraph (e)(3)(i).

(ii) Approved protective equipment
(designated PF in Figures Q–1, Q–2, and
Q–3) shall be installed in fuel-gas piping to prevent:
(A) Backflow of oxygen into the fuelgas supply system;
(B) Passage of a flash back into the
fuel-gas supply system; and
(C) Excessive back pressure of oxygen
in the fuel-gas supply system. The
three functions of the protective equipment may be combined in one device or
may be provided by separate devices.
(1) The protective equipment shall be
located in the main supply line, as in
Figure Q–1 or at the head of each
branch line, as in Figure Q–2 or at each
location where fuel-gas is withdrawn,

as in Figure Q–3. Where branch lines
are of 2-inch pipe size or larger or of
substantial length, protective equipment (designated as PF) shall be located as shown in either Q–2 and Q–3.
(2) Backflow protection shall be provided by an approved device that will
prevent oxygen from flowing into the
fuel-gas system or fuel from flowing
into the oxygen system (see SF, Figures
Q–1 and Q–2).
(3) Flash-back protection shall be
provided by an approved device that
will prevent flame from passing into
the fuel-gas system.
(4) Back-pressure protection shall be
provided by an approved pressure-relief
device set at a pressure not greater

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Occupational Safety and Health Admin., Labor
than the pressure rating of the backflow or the flashback protection device, whichever is lower. The pressurerelief device shall be located on the
downstream side of the backflow and
flashback protection devices. The vent
from the pressure-relief device shall be
at least as large as the relief device
inlet and shall be installed without low
points that may collect moisture. If
low points are unavoidable, drip pots
with drains closed with screw plugs or
caps shall be installed at the low
points. The vent terminus shall not endanger personnel or property through
gas discharge; shall be located away
from ignition sources; and shall terminate in a hood or bend.
(iii) If pipeline protective equipment
incorporates a liquid, the liquid level
shall be maintained, and a suitable
antifreeze may be used to prevent
freezing.
(iv) Fuel gas for use with equipment
not requiring oxygen shall be withdrawn upstream of the piping protective devices.
(4) Station outlet protective equipment.
(i) A check valve, pressure regulator,
hydraulic seal, or combination of these
devices shall be provided at each station outlet, including those on portable
headers, to prevent backflow, as shown
in Figures Q–1, Q–2, and Q–3 and designated as SF and SO.
(ii) When approved pipeline protective equipment (designated PF) is located at the station outlet as in Figure
Q–3, no additional check valve, pressure regulator, or hydraulic seal is required.
(iii) A shutoff valve (designated VF
and VO) shall be installed at each station outlet and shall be located on the
upstream side of other station outlet
equipment.
(iv) If the station outlet is equipped
with a detachable regulator, the outlet
shall terminate in a union connection
that complies with the Regulator Connection Standards, 1958, Compressed
Gas Association, which is incorporated
by reference as specified in § 1910.6.
(v) If the station outlet is connected
directly to a hose, the outlet shall terminate in a union connection complying with the Standard Hose Connection Specifications, 1957, Compressed

§ 1910.253

Gas Association, which is incorporated
by reference as specified in § 1910.6.
(vi) Station outlets may terminate in
pipe threads to which permanent connections are to be made, such as to a
machine.
(vii)
Station
outlets
shall
be
equipped with a detachable outlet seal
cap secured in place. This cap shall be
used to seal the outlet except when a
hose, a regulator, or piping is attached.
(viii) Where station outlets are
equipped with approved backflow and
flashback protective devices, as many
as four torches may be supplied from
one station outlet through rigid piping,
provided each outlet from such piping
is equipped with a shutoff valve and
provided the fuel-gas capacity of any
one torch does not exceed 15 cubic feet
(0.42 m3) per hour. This paragraph
(e)(4)(viii) does not apply to machines.
(5) Hose and hose connections. (i) Hose
for oxy-fuel gas service shall comply
with the Specification for Rubber
Welding Hose, 1958, Compressed Gas Association and Rubber Manufacturers
Association, which is incorporated by
reference as specified in § 1910.6.
(ii) When parallel lengths of oxygen
and acetylene hose are taped together
for convenience and to prevent tangling, not more than 4 inches (10.2 cm)
out of 12 inches (30.5 cm) shall be covered by tape.
(iii) Hose connections shall comply
with the Standard Hose Connection
Specifications, 1957, Compressed Gas
Association.
(iv) Hose connections shall be
clamped or otherwise securely fastened
in a manner that will withstand, without leakage, twice the pressure to
which they are normally subjected in
service, but in no case less than a pressure of 300 psi (2.04 MPa). Oil-free air or
an oil-free inert gas shall be used for
the test.
(v) Hose showing leaks, burns, worn
places, or other defects rendering it
unfit for service shall be repaired or replaced.
(6) Pressure-reducing regulators. (i)
Pressure-reducing regulators shall be
used only for the gas and pressures for
which they are intended. The regulator
inlet connections shall comply with
Regulator Connection Standards, 1958,
Compressed Gas Association.

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§ 1910.253

29 CFR Ch. XVII (7–1–05 Edition)

(ii) When regulators or parts of regulators, including gages, need repair, the
work shall be performed by skilled mechanics who have been properly instructed.
(iii) Gages on oxygen regulators shall
be marked ‘‘USE NO OIL.’’
(iv) Union nuts and connections on
regulators shall be inspected before use
to detect faulty seats which may cause
leakage of gas when the regulators are
attached to the cylinder valves.
(f) Acetylene generators—(1) Approval
and marking. (i) Generators shall be of
approved construction and shall be
plainly marked with the maximum
rate of acetylene in cubic feet per hour
for which they are designed; the weight
and size of carbide necessary for a single charge; the manufacturer’s name
and address; and the name or number
of the type of generator.
(ii) Carbide shall be of the size
marked on the generator nameplate.
(2) Rating and pressure limitations. (i)
The total hourly output of a generator
shall not exceed the rate for which it is
approved and marked. Unless specifically approved for higher ratings, carbide-feed generators shall be rated at 1
cubic foot (0.028 m3) per hour per pound
of carbide required for a single complete charge.
(ii) Relief valves shall be regularly
operated to insure proper functioning.
Relief valves for generating chambers
shall be set to open at a pressure not in
excess of 15 psig (103 kPa gauge pressure). Relief valves for hydraulic back
pressure valves shall be set to open at
a pressure not in excess of 20 psig (137
kPa gauge pressure).
(iii) Nonautomatic generators shall
not be used for generating acetylene at
pressures exceeding l psig (7 kPa gauge
pressure), and all water overflows shall
be visible.
(3) Location. The space around the
generator shall be ample for free, unobstructed operation and maintenance
and shall permit ready adjustment and
charging.
(4) Stationary acetylene generators
(automatic and nonautomatic). (i)(A) The
foundation shall be so arranged that
the generator will be level and so that
no excessive strain will be placed on
the generator or its connections.

Acetylene generators shall be grounded.
(B) Generators shall be placed where
water will not freeze. The use of common salt (sodium chloride) or other
corrosive chemicals for protection
against freezing is not permitted. (For
heating
systems
see
paragraph
(f)(6)(iii) of this section.)
(C) Except when generators are prepared in accordance with paragraph
(f)(7)(v) of this section, sources of ignition shall be prohibited in outside generator houses or inside generator
rooms.
(D) Water shall not be supplied
through a continuous connection to
the generator except when the generator is provided with an adequate open
overflow or automatic water shutoff
which will effectively prevent overfilling of the generator. Where a noncontinuous connection is used, the supply line shall terminate at a point not
less than 2 inches (5 cm) above the regularly provided opening for filling so
that the water can be observed as it enters the generator.
(E) Unless otherwise specifically approved, generators shall not be fitted
with continuous drain connections
leading to sewers, but shall discharge
through an open connection into a
suitably vented outdoor receptacle or
residue pit which may have such connections. An open connection for the
sludge drawoff is desirable to enable
the generator operator to observe leakage of generating water from the drain
valve or sludge cock.
(ii)(A) Each generator shall be provided with a vent pipe.
(B) The escape or relief pipe shall be
rigidly installed without traps and so
that any condensation will drain back
to the generator.
(C) The escape or relief pipe shall be
carried full size to a suitable point outside the building. It shall terminate in
a hood or bend located at least 12 feet
(3.7 m) above the ground, preferably
above the roof, and as far away as practicable from windows or other openings
into buildings and as far away as practicable from sources of ignition such as
flues or chimneys and tracks used by
locomotives. Generating chamber relief
pipes shall not be inter-connected but
shall be separately led to the outside

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Occupational Safety and Health Admin., Labor
air. The hood or bend shall be so constructed that it will not be obstructed
by rain, snow, ice, insects, or birds.
The outlet shall be at least 3 feet (0.9
m) from combustible construction.
(iii)(A) Gas holders shall be constructed on the gasometer principle,
the bell being suitably guided. The gas
bell shall move freely without tendency to bind and shall have a clearance
of at least 2 inches (5 cm) from the
shell.
(B) The gas holder may be located in
the generator room, in a separate room
or out of doors. In order to prevent collapse of the gas bell or infiltration of
air due to a vacuum caused by the compressor or booster pump or cooling of
the gas, a compressor or booster cutoff
shall be provided at a point 12 inches
(0.3 m) or more above the landing point
of the bell. When the gas holder is located indoors, the room shall be ventilated in accordance with paragraph
(f)(6)(ii) of this section and heated and
lighted in accordance with paragraphs
(f)(6)(iii) and (f)(6)(iv) of this section.
(C) When the gas holder is not located within a heated building, gas
holder seals shall be protected against
freezing.

§ 1910.253

(D) Means shall be provided to stop
the generator-feeding mechanism before the gas holder reaches the upper
limit of its travel.
(E) When the gas holder is connected
to only one generator, the gas capacity
of the holder shall be not less than onethird of the hourly rating of the generator.
(F) If acetylene is used from the gas
holder without increase in pressure at
some points but with increase in pressure by a compressor or booster pump
at other points, approved piping protective devices shall be installed in
each supply line. The low-pressure protective device shall be located between
the gas holder and the shop piping, and
the medium-pressure protective device
shall be located between the compressor or booster pump and the shop
piping (see Figure
Q–4). Approved
protective equipment (designated PF) is
used to prevent: Backflow of oxygen
into the fuel-gas supply system; passage of a flashback into the fuel-gas
supply system; and excessive back
pressure of oxygen in the fuel-gas supply system. The three functions of the
protective equipment may be combined
in one device or may be provided by
separate devices.

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§ 1910.253

29 CFR Ch. XVII (7–1–05 Edition)

(iv)(A) The compressor or booster
system shall be of an approved type.
(B) Wiring and electric equipment in
compressor or booster pump rooms or
enclosures shall conform to the provisions of subpart S of this part for Class
I, Division 2 locations.
(C) Compressors and booster pump
equipment shall be located in well-ventilated areas away from open flames,
electrical or mechanical sparks, or
other ignition sources.
(D) Compressor or booster pumps
shall be provided with pressure relief
valves which will relieve pressure exceeding 15 psig (103 kPa gauge pressure)
to a safe outdoor location as provided
in paragraph (f)(4)(ii) of this section, or
by returning the gas to the inlet side
or to the gas supply source.
(E) Compressor or booster pump discharge outlets shall be provided with
approved protective equipment. (See
paragraph (e) of this section.)
(5) Portable acetylene generators. (i)(A)
All portable generators shall be of a
type approved for portable use.
(B) Portable generators shall not be
used within 10 feet (3 m) of combustible
material other than the floor.

(C) Portable generators shall not be
used in rooms of total volume less than
35 times the total gas-generating capacity per charge of all generators in
the room. Generators shall not be used
in rooms having a ceiling height of less
than 10 feet (3 m). (To obtain the gasgenerating capacity in cubic feet per
charge, multiply the pounds of carbide
per charge by 4.5.)
(D) Portable generators shall be protected against freezing. The use of salt
or other corrosive chemical to prevent
freezing is prohibited.
(ii)(A) Portable generators shall be
cleaned and recharged and the air mixture blown off outside buildings.
(B) When charged with carbide, portable generators shall not be moved by
crane or derrick.
(C) When not in use, portable generators shall not be stored in rooms in
which open flames are used unless the
generators contain no carbide and have
been thoroughly purged of acetylene.
Storage rooms shall be well ventilated.
(D) When portable acetylene generators are to be transported and operated
on vehicles, they shall be securely anchored to the vehicles. If transported

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Occupational Safety and Health Admin., Labor
by truck, the motor shall be turned off
during charging, cleaning, and generating periods.
(E) Portable generators shall be located at a safe distance from the welding position so that they will not be exposed to sparks, slag, or misdirection
of the torch flame or overheating from
hot materials or processes.
(6) Outside generator houses and inside
generator rooms for stationary acetylene
generators. (i)(A) No opening in any
outside generator house shall be located within 5 feet (1.5 m) of any opening in another building.
(B) Walls, floors, and roofs of outside
generator houses shall be of noncombustible construction.
(C) When a part of the generator
house is to be used for the storage or
manifolding of oxygen cylinders, the
space to be so occupied shall be separated from the generator or carbide
storage section by partition walls continuous from floor to roof or ceiling, of
the type of construction stated in paragraph (f)(6)(i)(H) of this section. Such
separation walls shall be without openings and shall be joined to the floor,
other walls and ceiling or roof in a
manner to effect a permanent gas-tight
joint.
(D) Exit doors shall be located so as
to be readily accessible in case of emergency.
(E) Explosion venting for outside
generator houses and inside generator
rooms shall be provided in exterior
walls or roofs. The venting areas shall
be equal to not less than 1 square foot
(0.09 m2) per 50 cubic feet (1.4 m3) of
room volume and may consist of any
one or any combination of the following: Walls of light, noncombustible
material preferably single-thickness,
single-strength glass; lightly fastened
hatch covers; lightly fastened swinging
doors in exterior walls opening outward; lightly fastened walls or roof designed to relieve at a maximum pressure of 25 pounds per square foot (0.001
MPa).
(F) The installation of acetylene generators within buildings shall be restricted to buildings not exceeding one
story in height; provided, however, that
this will not be construed as prohibiting such installations on the roof or

§ 1910.253

top floor of a building exceeding such
height.
(G) Generators installed inside buildings shall be enclosed in a separate
room.
(H) The walls, partitions, floors, and
ceilings of inside generator rooms shall
be of noncombustible construction having a fire-resistance rating of at least 1
hour. The walls or partitions shall be
continuous from floor to ceiling and
shall be securely anchored. At least
one wall of the room shall be an exterior wall.
(I) Openings from an inside generator
room to other parts of the building
shall be protected by a swinging type,
self-closing fire door for a Class B
opening and having a rating of at least
1 hour. Windows in partitions shall be
wired glass and approved metal frames
with fixed sash. Installation shall be in
accordance with the Standard for the
Installation of Fire Doors and Windows, NFPA 80–1970, which is incorporated by reference as specified in
§ 1910.6.
(ii) Inside generator rooms or outside
generator houses shall be well ventilated with vents located at floor and
ceiling levels.
(iii) Heating shall be by steam, hot
water, enclosed electrically heated elements or other indirect means. Heating
by flames or fires shall be prohibited in
outside generator houses or inside generator rooms, or in any enclosure communicating with them.
(iv)(A) Generator houses or rooms
shall have natural light during daylight hours. Where artificial lighting is
necessary it shall be restricted to electric lamps installed in a fixed position.
Unless specifically approved for use in
atmospheres
containing
acetylene,
such lamps shall be provided with enclosures of glass or other noncombustible material so designed and constructed as to prevent gas vapors from
reaching the lamp or socket and to resist breakage. Rigid conduit with
threaded connections shall be used.
(B) Lamps installed outside of wiredglass panels set in gas-tight frames in
the exterior walls or roof of the generator house or room are acceptable.
(v) Electric switches, telephones, and
all other electrical apparatus which
may cause a spark, unless specifically

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§ 1910.253

29 CFR Ch. XVII (7–1–05 Edition)

approved for use inside acetylene generator rooms, shall be located outside
the generator house or in a room or
space separated from the generator
room by a gas-tight partition, except
that where the generator system is designed so that no carbide fill opening
or other part of the generator is open
to the generator house or room during
the operation of the generator, and so
that residue is carried in closed piping
from the residue discharge valve to a
point outside the generator house or
room, electrical equipment in the generator house or room shall conform to
the provisions of subpart S of this part
for Class I, Division 2 locations.
(7) Maintenance and operation. (i) Unauthorized persons shall not be permitted in outside generator houses or
inside generator rooms.
(A) Operating instructions shall be
posted in a conspicuous place near the
generator or kept in a suitable place
available for ready reference.
(B) When recharging generators the
order of operations specified in the instructions supplied by the manufacturer shall be followed.
(C) In the case of batch-type generators, when the charge of carbide is exhausted and before additional carbide
is added, the generating chamber shall
always be flushed out with water, renewing the water supply in accordance
with the instruction card furnished by
the manufacturer.
(D) The water-carbide residue mixture drained from the generator shall
not be discharged into sewer pipes or
stored in areas near open flames. Clear
water from residue settling pits may be
discharged into sewer pipes.
(ii) The carbide added each time the
generator is recharged shall be sufficient to refill the space provided for
carbide without ramming the charge.
Steel or other ferrous tools shall not be
used in distributing the charge.
(iii) Generator water chambers shall
be kept filled to proper level at all
times except while draining during the
recharging operation.
(iv) Whenever repairs are to be made
or the generator is to be charged or
carbide is to be removed, the water
chamber shall be filled to the proper
level.

(v) Previous to making repairs involving welding, soldering, or other hot
work or other operations which
produce a source of ignition, the carbide charge and feed mechanism shall
be completely removed. All acetylene
shall be expelled by completely flooding the generator shell with water and
the generator shall be disconnected
from the piping system. The generator
shall be kept filled with water, if possible, or positioned to hold as much
water as possible.
(vi) Hot repairs shall not be made in
a room where there are other generators unless all the generators and piping have been purged of acetylene.
(g) Calcium carbide storage—(1) Packaging. (i) Calcium carbide shall be contained in metal packages of sufficient
strength to prevent rupture. The packages shall be provided with a screw top
or equivalent. These packages shall be
constructed water- and air-tight. Solder shall not be used in such a manner
that the package would fail if exposed
to fire.
(ii) Packages containing calcium carbide shall be conspicuously marked
‘‘Calcium Carbide—Dangerous If Not
Kept Dry’’ or with equivalent warning.
(iii) Caution: Metal tools, even the
so-called spark resistant type may
cause ignition of an acetylene and air
mixture when opening carbide containers.
(iv) Sprinkler systems shall not be
installed in carbide storage rooms.
(2) Storage indoors. (i) Calcium carbide in quantities not to exceed 600
pounds (272.2 kg) may be stored indoors
in dry, waterproof, and well-ventilated
locations.
(A) Calcium carbide not exceeding 600
pounds (272.2 kg) may be stored indoors
in the same room with fuel-gas cylinders.
(B) Packages of calcium carbide, except for one of each size, shall be kept
sealed. The seals shall not be broken
when there is carbide in excess of 1
pound (0.5 kg) in any other unsealed
package of the same size of carbide in
the room.
(ii) Calcium carbide exceeding 600
pounds (272.2 kg) but not exceeding
5,000 pounds (2,268 kg) shall be stored:
(A) In accordance with paragraph
(g)(2)(iii) of this section;

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Occupational Safety and Health Admin., Labor
(B) In an inside generator room or
outside generator house; or
(C) In a separate room in a one-story
building which may contain other occupancies, but without cellar or basement beneath the carbide storage section. Such rooms shall be constructed
in
accordance
with
paragraphs
(f)(6)(i)(H) and (f)(6)(i)(I) of this section
and ventilated in accordance with
paragraph (f)(6)(ii) of this section.
These rooms shall be used for no other
purpose.
(iii) Calcium carbide in excess of 5,000
pounds (2,268 kg) shall be stored in onestory buildings without cellar or basement and used for no other purpose, or
in outside generator houses. If the storage building is of noncombustible construction, it may adjoin other onestory buildings if separated therefrom
by unpierced firewalls; if it is detached
less than 10 feet (3 m) from such building or buildings, there shall be no opening in any of the mutually exposing
sides of such buildings within 10 feet (3
m). If the storage building is of combustible construction, it shall be at
least 20 feet (6.1 m) from any other oneor two-story building, and at least 30
feet (9.1 m) from any other building exceeding two stories.
(3) Storage outdoors. (i) Calcium carbide in unopened metal containers may
be stored outdoors.
(ii) Carbide containers to be stored
outdoors shall be examined to make
sure that they are in good condition.
Periodic reexaminations shall be made
for rusting or other damage to a container that might affect its water or
air tightness.
(iii) The bottom tier of each row
shall be placed on wooden planking or
equivalent, so that the containers will
not come in contact with the ground or
ground water.
(iv) Containers of carbide which have
been in storage the longest shall be
used first.
[55 FR 13696, Apr. 11, 1990, as amended at 55
FR 32015, Aug 6, 1990; 55 FR 46053, Nov. 1, 1990;
61 FR 9241, Mar. 7, 1996]

§ 1910.254

Arc welding and cutting.

(a) General—(1) Equipment selection.
Welding equipment shall be chosen for
safe application to the work to be done

§ 1910.254

as specified in paragraph (b) of this section.
(2) Installation. Welding equipment
shall be installed safely as specified by
paragraph (c) of this section.
(3) Instruction. Workmen designated
to operate arc welding equipment shall
have been properly instructed and
qualified to operate such equipment as
specified in paragraph (d) of this section.
(b) Application of arc welding equipment—(1) General. Assurance of consideration of safety in design is obtainable
by choosing apparatus complying with
the Requirements for Electric ArcWelding Apparatus, NEMA EW–1–1962,
National Electrical Manufacturers Association or the Safety Standard for
Transformer-Type Arc-Welding Machines, ANSI C33.2—1956, Underwriters’
Laboratories, both of which are incorporated by reference as specified in
§ 1910.6.
(2)
Environmental
conditions.
(i)
Standard machines for arc welding
service shall be designed and constructed to carry their rated load with
rated temperature rises where the temperature of the cooling air does not exceed 40 °C (104 °F) and where the altitude does not exceed 3,300 feet (1,005.8
m), and shall be suitable for operation
in atmospheres containing gases, dust,
and light rays produced by the welding
arc.
(ii) Unusual service conditions may
exist, and in such circumstances machines shall be especially designed to
safely meet the requirements of the
service. Chief among these conditions
are:
(A) Exposure to unusually corrosive
fumes.
(B) Exposure to steam or excessive
humidity.
(C) Exposure to excessive oil vapor.
(D) Exposure to flammable gases.
(E) Exposure to abnormal vibration
or shock.
(F) Exposure to excessive dust.
(G) Exposure to weather.
(H) Exposure to unusual seacoast or
shipboard conditions.
(3) Voltage. The following limits shall
not be exceeded:
(i) Alternating-current machines
(A) Manual arc welding and cutting—
80 volts.

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§ 1910.254

29 CFR Ch. XVII (7–1–05 Edition)

(B) Automatic (machine or mechanized) arc welding and cutting—100
volts.
(ii) Direct-current machines
(A) Manual arc welding and cutting—
100 volts.
(B) Automatic (machine or mechanized) arc welding and cutting-100
volts.
(iii) When special welding and cutting processes require values of open
circuit voltages higher than the above,
means shall be provided to prevent the
operator from making accidental contact with the high voltage by adequate
insulation or other means.
(iv) For a.c. welding under wet conditions or warm surroundings where perspiration is a factor, the use of reliable
automatic controls for reducing no
load voltage is recommended to reduce
the shock hazard.
(4) Design. (i) A controller integrally
mounted in an electric motor driven
welder shall have capacity for carrying
rated motor current, shall be capable
of making and interrupting stalled
rotor current of the motor, and may
serve as the running overcurrent device
if provided with the number of overcurrent units as specified by subpart S of
this part.
(ii) On all types of arc welding machines, control apparatus shall be enclosed except for the operating wheels,
levers, or handles.
(iii) Input power terminals, tap
change devices and live metal parts
connected to input circuits shall be
completely enclosed and accessible
only by means of tools.
(iv) Terminals for welding leads
should be protected from accidental
electrical contact by personnel or by
metal objects, i.e., vehicles, crane
hooks, etc. Protection may be obtained
by use of: Dead-front receptacles for
plug connections; recessed openings
with nonremovable hinged covers;
heavy insulating sleeving or taping or
other equivalent electrical and mechanical protection. If a welding lead
terminal which is intended to be used
exclusively for connection to the work
is connected to the grounded enclosure,
it must be done by a conductor at least
two AWG sizes smaller than the
grounding conductor and the terminal

shall be marked to indicate that it is
grounded.
(v) No connections for portable control devices such as push buttons to be
carried by the operator shall be connected to an a.c. circuit of higher than
120 volts. Exposed metal parts of portable control devices operating on circuits above 50 volts shall be grounded
by a grounding conductor in the control cable.
(vi) Auto transformers or a.c. reactors shall not be used to draw welding
current directly from any a.c. power
source having a voltage exceeding 80
volts.
(c) Installation of arc weldinq equipment—(1) General. Installation including power supply shall be in accordance
with the requirements of subpart S of
this part.
(2) Grounding. (i) The frame or case of
the welding machine (except enginedriven machines) shall be grounded
under the conditions and according to
the methods prescribed in subpart S of
this part.
(ii) Conduits containing electrical
conductors shall not be used for completing a work-lead circuit. Pipelines
shall not be used as a permanent part
of a work-lead circuit, but may be used
during construction, extension or repair providing current is not carried
through threaded joints, flanged bolted
joints, or caulked joints and that special precautions are used to avoid
sparking at connection of the worklead cable.
(iii) Chains, wire ropes, cranes,
hoists, and elevators shall not be used
to carry welding current.
(iv) Where a structure, conveyor, or
fixture is regularly employed as a
welding current return circuit, joints
shall be bonded or provided with adequate current collecting devices.
(v) All ground connections shall be
checked to determine that they are
mechanically strong and electrically
adequate for the required current.
(3) Supply connections and conductors.
(i) A disconnecting switch or controller
shall be provided at or near each welding machine which is not equipped with
such a switch or controller mounted as
an integral part of the machine. The

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Occupational Safety and Health Admin., Labor
switch shall be in accordance with subpart S of this part. Overcurrent protection shall be provided as specified in
subpart S of this part. A disconnect
switch with overload protection or
equivalent disconnect and protection
means, permitted by subpart S of this
part, shall be provided for each outlet
intended for connection to a portable
welding machine.
(ii) For individual welding machines,
the rated current-carrying capacity of
the supply conductors shall be not less
than the rated primary current of the
welding machines.
(iii) For groups of welding machines,
the rated current-carrying capacity of
conductors may be less than the sum of
the rated primary currents of the welding machines supplied. The conductor
rating shall be determined in each case
according to the machine loading based
on the use to be made of each welding
machine and the allowance permissible
in the event that all the welding machines supplied by the conductors will
not be in use at the same time.
(iv) In operations involving several
welders on one structure, d.c. welding
process requirements may require the
use of both polarities; or supply circuit
limitations for a.c. welding may require distribution of machines among
the phases of the supply circuit. In
such cases no load voltages between
electrode holders will be 2 times normal in d.c. or 1, 1.41, 1.73, or 2 times
normal on a.c. machines. Similar voltage differences will exist if both a.c.
and d.c. welding are done on the same
structure.
(A) All d.c. machines shall be connected with the same polarity.
(B) All a.c. machines shall be connected to the same phase of the supply
circuit and with the same instantaneous polarity.
(d) Operation and maintenance—(1)
General. Workmen assigned to operate
or maintain arc welding equipment
shall be acquainted with the requirements of this section and with § 1910.252
(a), (b) and (c) of this part; if doing gasshielded
arc
welding,
also
Recommended Safe Practices for GasShielded Arc Welding, A6.1–1966, American Welding Society, which is incorporated by reference as specified in
§ 1910.6.

§ 1910.254

(2) Machine hook up. Before starting
operations all connections to the machine shall be checked to make certain
they are properly made. The work lead
shall be firmly attached to the work;
magnetic work clamps shall be freed
from adherent metal particles of spatter on contact surfaces. Coiled welding
cable shall be spread out before use to
avoid serious overheating and damage
to insulation.
(3) Grounding. Grounding of the welding machine frame shall be checked.
Special attention shall be given to
safety ground connections of portable
machines.
(4) Leaks. There shall be no leaks of
cooling water, shielding gas or engine
fuel.
(5) Switches. It shall be determined
that proper switching equipment for
shutting down the machine is provided.
(6) Manufacturers’ instructions. Printed rules and instructions covering operation of equipment supplied by the
manufacturers shall be strictly followed.
(7) Electrode holders. Electrode holders when not in use shall be so placed
that they cannot make electrical contact with persons, conducting objects,
fuel or compressed gas tanks.
(8) Electric shock. Cables with splices
within 10 feet (3 m) of the holder shall
not be used. The welder should not coil
or loop welding electrode cable around
parts of his body.
(9) Maintenance. (i) The operator
should report any equipment defect or
safety hazard to his supervisor and the
use of the equipment shall be discontinued until its safety has been assured. Repairs shall be made only by
qualified personnel.
(ii) Machines which have become wet
shall be thoroughly dried and tested
before being used.
(iii) Cables with damaged insulation
or exposed bare conductors shall be replaced. Joining lengths of work and
electrode cables shall be done by the
use of connecting means specifically
intended for the purpose. The connecting means shall have insulation
adequate for the service conditions.
[55 FR 13696, Apr. 11, 1990, as amended at 61
FR 9241, Mar. 7, 1996]

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§ 1910.255

29 CFR Ch. XVII (7–1–05 Edition)

§ 1910.255 Resistance welding.
(a) General—(1) Installation. All equipment shall be installed by a qualified
electrician in conformance with subpart S of this part. There shall be a
safety-type disconnecting switch or a
circuit breaker or circuit interrupter
to open each power circuit to the machine, conveniently located at or near
the machine, so that the power can be
shut off when the machine or its controls are to be serviced.
(2) Thermal protection. Ignitron tubes
used in resistance welding equipment
shall be equipped with a thermal protection switch.
(3) Personnel. Workmen designated to
operate resistance welding equipment
shall have been properly instructed and
judged competent to operate such
equipment.
(4) Guarding. Controls of all automatic or air and hydraulic clamps shall
be arranged or guarded to prevent the
operator from accidentally activating
them.
(b) Spot and seam welding machines
(nonportable)—(1) Voltage. All external
weld initiating control circuits shall
operate on low voltage, not over 120
volts, for the safety of the operators.
(2) Capacitor welding. Stored energy
or capacitor discharge type of resistance welding equipment and control
panels involving high voltage (over 550
volts) shall be suitably insulated and
protected by complete enclosures, all
doors of which shall be provided with
suitable interlocks and contacts wired
into the control circuit (similar to elevator interlocks). Such interlocks or
contacts shall be so designed as to effectively interrupt power and short circuit all capacitors when the door or
panel is open. A manually operated
switch or suitable positive device shall
be installed, in addition to the mechanical interlocks or contacts, as an added
safety measure assuring absolute discharge of all capacitors.
(3) Interlocks. All doors and access
panels of all resistance welding machines and control panels shall be kept
locked and interlocked to prevent access, by unauthorized persons, to live
portions of the equipment.
(4) Guarding. All press welding machine operations, where there is a possibility of the operator’s fingers being

under the point of operation, shall be
effectively guarded by the use of a device such as an electronic eye safety
circuit, two hand controls or protection similar to that prescribed for
punch press operation, § 1910.217 of this
part. All chains, gears, operating bus
linkage, and belts shall be protected by
adequate guards, in accordance with
§ 1910.219 of this part.
(5) Shields. The hazard of flying
sparks shall be, wherever practical,
eliminated by installing a shield guard
of safety glass or suitable fire-resistant
plastic at the point of operation. Additional shields or curtains shall be installed as necessary to protect passing
persons from flying sparks. (See
§ 1910.252(b)(2)(i)(C) of this part.)
(6) Foot switches. All foot switches
shall be guarded to prevent accidental
operation of the machine.
(7) Stop buttons. Two or more safety
emergency stop buttons shall be provided on all special multispot welding
machines, including 2-post and 4-post
weld presses.
(8) Safety pins. On large machines,
four safety pins with plugs and receptacles (one in each corner) shall be provided so that when safety pins are removed and inserted in the ram or platen, the press becomes inoperative.
(9) Grounding. Where technically
practical, the secondary of all welding
transformers used in multispot, projection and seam welding machines shall
be grounded. This may be done by permanently grounding one side of the
welding secondary current circuit.
Where not technically practical, a center tapped grounding reactor connected
across the secondary or the use of a
safety disconnect switch in conjunction with the welding control are acceptable alternates. Safety disconnect
shall be arranged to open both sides of
the line when welding current is not
present.
(c) Portable welding machines—(1)
Counterbalance. All portable welding
guns
shall
have
suitable
counterbalanced devices for supporting
the guns, including cables, unless the
design of the gun or fixture makes
counterbalancing impractical or unnecessary.

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Occupational Safety and Health Admin., Labor
(2) Safety chains. All portable welding
guns, transformers and related equipment that is suspended from overhead
structures, eye beams, trolleys, etc.,
shall be equipped with safety chains or
cables. Safety chains or cables shall be
capable of supporting the total shock
load in the event of failure of any component of the supporting system.
(3) Clevis. Each clevis shall be capable
of supporting the total shock load of
the suspended equipment in the event
of trolley failure.
(4) Switch guards. All initiating
switches, including retraction and dual
schedule switches, located on the portable welding gun shall be equipped with
suitable guards capable of preventing
accidental initiation through contact
with fixturing, operator’s clothing, etc.
Initiating switch voltage shall not exceed 24 volts.
(5) Moving holder. The movable holder, where it enters the gun frame, shall
have sufficient clearance to prevent
the shearing of fingers carelessly
placed on the operating movable holder.
(6) Grounding. The secondary and
case of all portable welding transformers shall be grounded. Secondary
grounding may be by center tapped secondary or by a center tapped grounding
reactor connected across the secondary.
(d) Flash welding equipment—(1) Ventilation and flash guard. Flash welding
machines shall be equipped with a hood
to control flying flash. In cases of high
production, where materials may contain a film of oil and where toxic elements and metal fumes are given off,
ventilation shall be provided in accordance with § 1910.252(c) of this part.
(2) Fire curtains. For the protection of
the operators of nearby equipment,
fire-resistant curtains or suitable
shields shall be set up around the machine and in such a manner that the
operators movements are not hampered.
(e) Maintenance. Periodic inspection
shall be made by qualified maintenance
personnel, and a certification record
maintained. The certification record
shall include the date of inspection, the
signature of the person who performed
the inspection and the serial number,
or other identifier, for the equipment

§ 1910.261

inspected. The operator shall be instructed to report any equipment defects to his supervisor and the use of
the equipment shall be discontinued
until safety repairs have been completed.

Subpart R—Special Industries
AUTHORITY: Sections 4, 6, and 8 of the Occupational Safety and Health Act of 1970, 29
U.S.C. 653, 655, and 657; Secretary of Labor’s
Order No. 12–71 (36 FR 8754), 8–76 (41 FR
25059), 9–83 (48 FR 35736), 1–90 (55 FR 9033), 6–
96 (62 FR 111), or 3–2000 (65 FR 50017), as applicable, and 29 CFR part 1911.

§ 1910.261 Pulp,
board mills.

paper,

and

(a) General requirements—(1) Application. This section applies to establishments where pulp, paper, and paperboard are manufactured and converted.
This section does not apply to logging
and the transportation of logs to pulp,
paper, and paperboard mills.
(2) Standards incorporated by reference.
Standards covering issues of occupational safety and health which have
general application without regard to
any specific industry are incorporated
by reference in paragraphs (b) through
(m) of this section and in subparagraphs (3) and (4) of this paragraph and
made applicable under this section.
Such standards shall be construed according to the rules set forth in § 1910.5.
(3) General incorporation of standards.
Establishments subject to this section
shall comply with the following standards of the American National Standards Institute, which are incorporated
by reference as specified in § 1910.6:
(i) Practice for Industrial Lighting,
A11.1—1965 (R–1970).
(ii) Scheme for the Identification of
Piping Systems, A13.1—1956.
(iii) Safety Code for Elevators,
Dumbwaiters, and Moving Walks,
A17.1—1965,
including
Supplements
A17.1a—1967, A17.1b—1968, A17.1c—1969,
and A17.1d—1970.
(iv) Practice for the Inspection of
Elevators (Inspector’s Manual), A17.2—
1960, including Suppelements A17.2a—
1965 and A17.2b—1967.
(v) Safety Code for Conveyors,
Cableways, and Related Equipment,
B20.1—1957.

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