Flashback arrestors prevents the back fire from the cutting torch coming back up the hoses (possibly rupturing it) and entering the cylinder (creating a blast). The flashback arrestor will prevent the flame from entering the cylinder. Separate flashback arrestors are used at the torch end and at the regulator end. The flashback arrestor at the cylinder end has a thermal cut-off valve that closes the gas flow through a melting process before the flame passes through the gate. Only FBA's conforming to EN 730 and ISO 5175 standard, which are BAM approved and carry a product liability insurance serve the purpose for which they are intended. FBA should also be tested and calibrated every year.