Flashback Arrestors FAQs
Straight answers to the questions people ask most when choosing, fitting and looking after flashback arrestors.
Should I fit flashback arrestors at the regulator, at the torch, or both?
Regulator-mounted arrestors screw on between the regulator and the hose and protect the regulator and the cylinder. Torch-mounted arrestors fit at the torch end of the hose and protect the hose and the equipment behind it as well.
Fitting them at both ends gives the most complete protection and is widely regarded as good practice, because a flashback can travel back along the hose and damage it before it reaches the regulator. Your risk assessment and the equipment maker's instructions will say what is required for your work.
What is the difference between resettable and non-resettable arrestors?
After a flashback, a resettable arrestor can be put back into service by following the maker's reset procedure, usually once the cause has been found and the unit has been checked. A non-resettable arrestor has done its job once and must be replaced.
Resettable types are convenient and are common on modern equipment, but they still need to be tested and inspected as the maker directs. If an arrestor has stopped a flashback, treat the rest of the hose and equipment with suspicion and have it all checked before using it again.
Can I use an oxygen arrestor on a fuel gas line, or the other way round?
No. Arrestors are made for a specific gas and are marked accordingly. Fuel gas arrestors normally have left-hand threaded connections, usually shown by a notch cut in the nut, while oxygen ones have right-hand threads. This is deliberate, to stop gases being connected the wrong way round.
Fuel gas types also differ from one another in their design, so use one that is marked as suitable for the gas you are running, whether acetylene or propane. Never force a connection that does not fit, and never use adaptors to get round the thread difference.
How often should flashback arrestors be tested and replaced?
There is no single interval that suits every arrestor. The maker's instructions for your own unit give the test method, how often to check it, and any maximum service life, so read them and check the markings or date on the body.
In general, arrestors should be inspected regularly, with a check of the non-return valve and a leak check on the connections. Check more often if the equipment is used hard, in dirty conditions or has been involved in a flashback. Many workshops include them in a routine inspection of all gas equipment and keep a record.
If an arrestor fails a check, is damaged, or has passed its service life, take it out of use and replace it. Your risk assessment will say what is required for your work.