Oxy-Acetylene Cutting Safety

Oxy-acetylene cutting uses a mixture of oxygen and acetylene gas to produce a flame hot enough to cut through steel.
Acetylene is extremely flammable and can decompose explosively if stored, handled, or used incorrectly.
Oxygen, while not flammable itself, supports combustion aggressively — oil or grease on oxygen equipment causes ignition.
Flash-back arrestors must be fitted to both the oxygen and acetylene regulators to prevent flame travelling back into cylinders.
Cylinders must be secured upright, separated by type, and stored in a ventilated area away from ignition sources.
A hot works permit is required before any oxy-acetylene cutting operation begins on a construction site.
Hoses and connections must be inspected before use — perished, damaged, or leaking hoses cause fires and explosions.
The correct lighting procedure is: open acetylene first, light the flame, then open oxygen to adjust the cutting jet.
The correct shutdown procedure is: close oxygen first, then acetylene — this prevents flashback and sooting of the tip.
Cylinder valves must be closed and caps replaced when equipment is not in active use, even during short breaks.

Explosive decomposition	Acetylene becomes unstable above 1.5 bar gauge pressure — incorrect handling or storage causes spontaneous decomposition and explosion.
Flashback	Flame travelling back through the hoses into the cylinder causes a catastrophic explosion — flash-back arrestors prevent this.
Oxygen enrichment	Oil or grease in contact with high-pressure oxygen ignites spontaneously — all oxygen equipment must be scrupulously clean and grease-free.

Do

Don't

Fit flash-back arrestors to both oxygen and acetylene regulators before use.
Secure cylinders upright and separate oxygen from acetylene by at least three metres.
Obtain a hot works permit before starting any oxy-acetylene cutting operation.
Inspect all hoses, connections, and regulators for damage and leaks before use.
Follow the correct lighting sequence: acetylene first, then oxygen for adjustment.
Follow the correct shutdown sequence: oxygen first, then close the acetylene valve.
Close cylinder valves and replace caps when equipment is not in active use.
Keep oil, grease, and petroleum products away from all oxygen equipment.
Clear combustible materials from the area and maintain a fire watch during cutting.
Ensure the operator is trained in oxy-acetylene cutting procedures and hazards.

DON'T use oxy-acetylene equipment without flash-back arrestors fitted on both lines.
DON'T store oxygen and acetylene cylinders together — maintain the three-metre separation.
DON'T cut with oxy-acetylene without a valid hot works permit in place.
DON'T use equipment with perished, cracked, or leaking hoses and connections.
DON'T reverse the lighting or shutdown sequence — it causes flashback and tip damage.
DON'T leave cylinder valves open during breaks — close them and relieve hose pressure.
DON'T use oily gloves or rags near oxygen regulators, valves, or fittings.
DON'T cut near flammable materials without clearing the area and posting a fire watch.
DON'T exceed 1.5 bar working pressure on acetylene — it becomes dangerously unstable.
DON'T attempt oxy-acetylene cutting without proper training in the equipment and process.

See also: Welding Safety | LPG and Gas Cylinder Storage

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