The Definition of Acetylene Safety

Definition of Acetylene Safety

Acetylene safety is the set of practices for storing, moving, connecting and using acetylene, a highly flammable fuel gas burned with oxygen for cutting, welding, brazing and heating. Acetylene ignites easily across a very wide range of concentrations in air and becomes unstable under pressure, which is why it is dissolved in acetone inside cylinders packed with a porous filler and must never be used at pressures above 15 psig. OSHA addresses acetylene in 29 CFR 1910.102 and 1910.253 for general industry and 1926.350 for construction.

Key Facts About Acetylene Safety

• Never use free acetylene at a pressure above 15 psig (103 kPa).
• Store, transport and use acetylene cylinders valve end up so acetone isn't drawn out with the gas.
• Separate stored oxygen cylinders from fuel gas cylinders by at least 20 feet, or by a noncombustible barrier at least 5 feet high with a fire-resistance rating of at least half an hour.
• Install flashback arrestors and reverse-flow check valves on the torch and regulator connections.
• Keep unalloyed copper and high-copper alloys out of acetylene service, since they can form shock-sensitive compounds.

Example of Acetylene Safety

Before a cutting job, a welder secures the oxygen and acetylene cylinders upright on a cart with a chain, checks that flashback arrestors are fitted, sets the acetylene regulator well below 15 psig, leak-tests connections with a compatible solution, and confirms the hot work permit and fire watch are in place.

How to Handle Acetylene Cylinders Safely

1. Inspect cylinders, valves, regulators and hoses for damage or contamination before use.
2. Secure cylinders upright so they can't tip or fall.
3. Crack the cylinder valve only as much as needed, typically no more than about one and a half turns, and leave the valve wrench in place for quick shutoff.
4. Purge lines and light the torch using the manufacturer's procedure.
5. Close cylinder valves and bleed lines when work stops, and always when cylinders are moved.
6. Store cylinders in a ventilated area away from heat, ignition sources and oxygen cylinders.

Related Terms

• Gas Cylinder Safety
• Fire Watch
• Lower Explosive Limit (LEL)
• Ignition Source

Frequently Asked Questions: Acetylene Safety

Why can't acetylene be used above 15 psig?

Above about 15 psig, acetylene can decompose violently on its own, even without air, so regulators and work practices keep it below that pressure in hoses and torches.

What is flashback and how is it prevented?

Flashback is a flame that travels back through the torch into the hoses or regulator, which can cause a hose fire or cylinder explosion. Flashback arrestors, check valves, correct purging and lighting procedures, and proper pressure settings prevent it.

What should I do if an acetylene cylinder leaks or catches fire?

If it is safe to do so, close the cylinder valve. Otherwise evacuate the area, keep people away, and call emergency responders. A heated acetylene cylinder can fail violently, so responders treat it as an explosion hazard.