What happened?

A group of students were welding using a set of oxy-acetylene torches supplied by a manifold system. A welding spark started a small fire near the top of the acetylene gas cylinder at the gas regulator connection.  A course assistant saw the fire and responded quickly, evacuating the students from the building and immediately extinguishing the fire using an ABC fire extinguisher. They then closed the acetylene gas valve and manifold system.

Fortunately, no injury resulted. Direct fire damage was limited to the pressure gauge on the acetylene regulator.

What was the cause of the incident?

The immediate cause of the incident was a leak at the threading of the gas regulator and the cylinder’s valve outlet. A spark generated during welding activities landed near the top of the cylinder and ignited the fire. Post-incident, a small gouge in the female valve seat of the acetylene gas cylinder was found, which could have contributed to the initial leak.

What went right?

When the fire was spotted, the course assistant promptly evacuated students from the shop and properly used the fire extinguisher to put out the fire.  As soon as they were able, they closed off the gas cylinder valve.

What should have been done differently?

Before using a fire extinguisher, always pull the closest fire alarm. The activated fire alarm system will immediately alert others to evacuate the building and notify the fire department to respond.

How can incidents like this be prevented?

Such a leak could have been caught by a bubble leak test.  Whenever setting up a compressed gas cylinder/ system, always conduct leak testing before initial use. For this and other safe practices with gas cylinder use, refer to the General Use SOP for Compressed Gases.