• The investigation revealed the possible cause of the explosion was related to the fitting of non-tested flashback arrestors. Subsequent testing on similar flashback arrestors revealed that they had failed a flow test and reverse flow test. 
• The gas cylinders in the rear of the vehicle may have been set up in such a way that when the ignited gas vented from the acetylene cylinder, it melted a hole into the oxygen cylinder, causing an explosion.

1. A person who designs, manufactures, imports or supplies plant (flashback arrestors) for use at a workplace shall, so far as practicable, ensure that they have undergone the relevant testing and examination so persons are not exposed to a hazard.
2. Gas cylinders intended to be used at a workplace where welding and allied processes are done need to be stored and maintained appropriately.  Where oxygen and acetylene cylinders are used adjacent to each other, consideration should be given to protecting the oxygen cylinder by placing a non-flammable shield between the cylinders.
3. Flashback arrestors should comply with Australian Standard AS4603-1999: Flashback arrester - safety devices for use with fuel gases and oxygen or compressed air.
4. Each flashback arrestor should be marked with the following information:
   1. the number of the relevant standard (ie AS 4603);
   2. the name or trademark of the manufacturer and/or distributor;
   3. the model or code number relating to the manufacturer’s installation instructions;
   4. the direction of the gas flow (normally an arrow);
   5. name of gas;
   6. the maximum working pressure expressed in bars or kilopascals;
   7. the date of manufacture and batch number, by coding, if necessary;
   8. proper colour coding of safety devices – blue for oxygen and red for fuel gas service (the markings should comply with the British Standard BS EN 730); and
   9. the country of manufacture.

• The Welding Technology Institute of Australia Technical Note No. 7 – Health and Safety in Welding.
• AS4603-1999: Flashback arrester - safety devices for use with fuel gases and oxygen or compressed air.
• BS EN 730 – Gas welding equipment – Safety devices – Part 1: Devices incorporating a flame (flashback) arrestor.
• Commission for Occupational Safety and Health Guidance note – Gas welding safety flash back arresters

Further information can be obtained from WorkSafe’s website or by contacting customer service on 1300 307 877 or email safety@demirs.wa.gov.au