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Subchapter 7. General Industry Safety Orders
Group 10. Gas Systems for Welding and Cutting
Article 87. Operating Procedure

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§4845. General Precautions.

(a) Mixtures of fuel gases and air or oxygen may be explosive and shall be guarded against. No device or attachment facilitating or permitting mixture of air or oxygen with combustible gases prior to consumption, except at the burner or in a standard torch or blowpipe, shall be allowed unless approved for the purpose.

(b) 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. The backflow protection device shall be installed on either the torch or at each station outlet (i.e., the point at which gas is withdrawn from the permanent piping) either upstream or downstream of the shutoff valve for the oxygen or fuel gas station outlet valve(s).

(c) Acetylene shall not be generated, piped (except in approved cylinder manifolds) or utilized at a pressure in excess of 15 pounds per square inch gauge pressure.

(d) The use of liquid acetylene shall be prohibited.

(e) Oil or grease shall not be permitted to come in contact with oxygen cylinders, valves, regulators or other fittings. Oxygen cylinders and apparatus shall not be handled with oily hands or gloves, or greasy materials. A jet of oxygen shall not be permitted to strike an oily surface, greasy clothes or enter a fuel oil or other storage tank.

(f) Oxygen shall not be used from a cylinder or cylinder manifold unless a pressure-reducing device intended for use with oxygen, and so marked, is provided.

(g) Fuel-gas shall not 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.

NOTE: Low pressure air-gas torches may be used on small cylinders provided there is no shutoff valve on the torch.

(h) Welding 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. 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.

(i) Cylinders shall be handled carefully.

NOTE: Rough handling, knocks, and falls are liable to damage the cylinder, valve or safety devices and result in leakage.

(j) Before connecting a regulator to a cylinder valve, the valve shall be opened slightly and closed immediately. (This action is generally termed "cracking" and is intended to clear the valve of dust or dirt that might otherwise enter the regulator.) The valve shall be opened while standing to one side of the outlet; never in front of it. A fuel-gas cylinder valve shall never be opened up, cracked near other welding work or near sparks, flame, or other possible sources of ignition.

EXCEPTION: Hydrogen cylinders. See suppliers instructions before connecting the regulator.

(k) Before a regulator is removed from a cylinder valve, the cylinder valve shall be closed and the gas released from the regulator.

(l) 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.

(m) Cylinders having leaking fuse plugs or other leaking safety devices shall be plainly tagged, and the supplier shall be promptly notified of the condition and his instructions followed. A warning shall be placed near the cylinders prohibiting any approach to them with a lighted cigarette or other source of ignition.

(n) Safety devices shall not be tampered with.

(o) The cylinder valve shall always be opened slowly.

(p) An acetylene cylinder valve shall not be opened more than one and one-half turns of the spindle, and preferably no more than three-fourths of a turn.

(q) Torches in use shall be inspected at the beginning of each working shift for leaking shutoff valves, hose couplings, and tip connections. Defective torches shall not be used. Clogged torch tip openings shall be cleaned with suitable cleaning wires, drills, or other devices designed for such purpose.

(r) Torches shall be lighted by friction lighters or other approved devices, and not by matches or from hot work.

(s) Unalloyed copper shall not be used for acetylene or acetylenic compounds except in listed equipment.

(t) 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.

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.

(u) If pipeline protective equipment incorporates a liquid, the liquid level shall be maintained, and a suitable antifreeze may be used to prevent freezing.

(v) 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 fire-resistant shields shall be provided.

(w) 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.

(x) Cylinders containing oxygen or acetylene or other fuel or gas shall not be taken into confined spaces.

(y) When operations are suspended for any substantial period of time, such as during lunch or overnight, gas cylinders shall be shut off. Where practicable the torch and hose shall be removed from the confined space. Upon completion or discontinuance of welding operations, the welder shall provide some means of warning other workers of the location of hot metal.

NOTE: See Section 5150 for ventilation requirements for welding, brazing and cutting.

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Amendment filed 5-16-75; effective thirtieth day thereafter (Register 75, No. 20).

2. Amendment filed 7-13-78; effective thirtieth day thereafter (Register 78, No. 28).

3. Amendment of subsection (r) filed 12-12-84; effective thirtieth day thereafter (Register 84, No. 50).

4. Amendment filed 6-12-87; operative 7-12-87 (Register 87, No. 26).

5. Amendment of subsection (b) filed 3-23-98; operative 4-22-98 (Register 98, No. 13).

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