A flashback arrestor, also known as a flash arrestor, is a special gas safety device that is used to stop the flame.
Backfire is when the flame goes into the nozzle or torch with a hard popping sound. Once the flame has entered into the nozzle it will keep burning inside causing a hissing or whistling sound. To avoid this regulators should be set at the right pressure and a light has been applied before a fuel flow is made.