The ignition of an explosive gas in a tank or pipe will trigger a deflagration (explosion). If a flame front propagates through a pipe, its speed will increase proportionally to the length of the pipe. If a pipe is shorter than 50 times it internal pipe diameter, the flame will propagate at subsonic speed. In this case, securing the protected side with a deflagration flame arrester will be sufficient. In general, a deflagration flame arrester operates at a lower pressure drop than a detonation flame arrester.
