Safety alert 02/2014 - Flashback arrestors

This publication is for: 
Employee / workerEmployer

A plumber was in the process of heating up some copper piping to ready it for brazing. They had run the hoses from the oxy-acetylene cylinders, which were stored in an aluminium frame in the rear of the worker’s utility to his work area, which was approximately 30 metres away. A short time after the worker ignited the gas at the blowpipe end, he heard an explosion outside.  He went outside and saw his work vehicle engulfed in flames. No-one was injured in this incident, but there was significant potential for serious injury or death. 

Flashback arrestors were fitted to both the operator’s side of the cylinders and to the blowpipe.

Contributing factors

  • 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.

Action required

  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.

Further information

  • 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

This Alert contains safety information following inquiries made by WorkSafe about an incident or unsafe practice. The information contained in this Alert does not necessarily include the outcome of WorkSafe’s action with respect to an incident. WorkSafe does not warrant the information in this Alert is complete or up to date and does not accept any liability to any person for the information in this report or as to its use.

Last updated 29 Jun 2017

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