The overpressure exhaust valve is installed on the upper right side of the backpack; The purpose is twofold: (1) Exhaust the heat and sweat from the human body in the protective clothing out of the clothing through the vent valve, and keep the body of the staff dry and comfortable as much as possible; (2) Positive pressure gas can squeeze out the toxic, harmful and strongly corrosive gas outside of the protective clothing when the protective clothing is accidentally punctured or punctured, so as to ensure the safety of personnel in unexpected situations. Important safety precautions.