The present invention offers a solution to the potential hazards associated with an accidental overheating of a full compressed gas cartridge, by offering an automatic heat-actuable pressure discharge system. The compressed gas cartridge is protected from dangerous explosions caused by excessive heat by the use of a lance that pierces the compressed gas cartridge safely when a spring loaded hammer is released from its constraints when a length of heat sensitive material fails in the presence of excessive heat, thereby avoiding a very serious fire hazard.