Acetylene Safety

Acetylene burns hotter than any other common fuel gas, which makes it great for cutting and welding. It’s also unstable. Under too much pressure it can break down and explode on its own, even without air. Acetylene cylinders are built differently from other gas cylinders, and they need different handling.

• Construction
• General Industry
• Welding

Never above 15 psig

Free acetylene gas must not be used at pressures above 15 psig (pounds per square inch gauge). Above that, it can decompose violently. Most regulator gauges have a red zone above 15 psig. Never set the working pressure into the red. OSHA’s welding rules (29 CFR 1910.253 and 1926.350) include this limit.

What’s inside the cylinder

An acetylene cylinder is packed with a porous material soaked in a liquid solvent (usually acetone). The acetylene dissolves into the solvent so it can be stored safely. That design explains several rules:

• Store and use cylinders upright. If a cylinder has been lying down, stand it up and wait before using it, at least as long as it was on its side or as the supplier directs. Otherwise liquid acetone can flow into the regulator and hose.
• Don’t draw gas too fast. High flow pulls acetone out with the gas. Follow the supplier’s withdrawal limit, often about one-seventh of the cylinder’s contents per hour. Use larger cylinders or a manifold for big tips and heating torches.

Valves and fittings

• Open the cylinder valve slowly, no more than about 1½ turns, so it can be shut quickly in an emergency.
• If the cylinder uses a valve wrench, leave the wrench on the valve while the cylinder is in use.
• Stand to the side of the regulator, not in front, when opening the valve.
• Check connections with leak-test solution, never with a flame.
• Use flashback arrestors and check valves. See Flashback Arrestors.

• Don’t use copper fittings or tubing with high copper content (over about 65% copper) with acetylene. It can form acetylides that explode on impact. Use fittings made for acetylene.
• Don’t try to repair cylinder valves or fusible plugs, or mix gases in a cylinder.

Storage and transport

• Store upright, secured with chains or straps, with valve caps on when not in use.
• Keep acetylene and other fuel gases at least 20 feet from oxygen cylinders in storage, or separated by a 5-foot-high noncombustible barrier with a half-hour fire rating. See Compressed Gas Cylinders.
• Keep cylinders away from heat, sparks and electrical circuits.
• Transport upright and secured, in a ventilated vehicle, never in a closed trunk or van cab.

If a cylinder overheats or catches fire

Acetylene cylinders have fusible plugs that melt at around 212°F to release gas before the cylinder ruptures. If a cylinder is hot, burning at the valve, or was in a fire, evacuate the area and call 911. Acetylene can keep decomposing inside a cylinder after the fire is out. Let the fire department handle it, and tell the gas supplier.

Before you light up

• Cylinder upright, secured and not recently laid down
• Regulator set at or below 15 psig
• Valve opened 1½ turns or less, wrench in place
• Flashback arrestors and check valves installed
• Hoses and connections leak-tested
• Hot work permit and fire watch in place. See Hot Work Permits

Last updated: October 2, 2026