Automatic pressure relief device is installed on the walls within the range of gas automatic fire extinguishing system protection, is an integral part of gas fire extinguishing system, usually in closed position.When fire occurs, the gas fire extinguishing agent is discharge to keep the area, causing reserve instant internal pressure increase, reach a set pressure, automatic pressure release mouth open, ensure building palisade structure does not execcd the permitted pressure, when pressure is reduced, the pressure mouth closed, and guarantee the sealing of the reserve, meet the needs of the design fire extinguishing fire extinguishing concentration.