Sometimes there will be gas in the pipeline, or there will be gas overflow in the system, especially at the beginning of operation, which is air. After the water comes, the gas will be squeezed out, and the gas will climb up the pipeline and eventually gather at the highest point of the system. While the exhaust valve is generally installed at the highest point of the system, when the gas enters the exhaust valve chamber, it gathers at the upper part of the exhaust valve. When the pressure rises, when the gas pressure is greater than the system pressure, the gas will make the water surface in the chamber drop, the buoy will drop with the water level, and the exhaust port will be opened; After the gas is exhausted, the water level rises, the buoy rises with it, and the exhaust port is closed. In the same way, when negative pressure is generated in the system, the water surface in the valve chamber drops, and the exhaust port opens, because the external atmospheric pressure is larger than the system pressure at this time, the atmosphere will enter the system through the exhaust port to prevent the harm of negative pressure. If the valve cap on the exhaust valve body is tightened, the exhaust valve stops venting. Normally, the valve cap should be in the open state. The exhaust valve can also be used with the block valve to facilitate the maintenance of the exhaust valve.