A gas valve is a component of a compressor that controls the flow of gas into and out of a cylinder. Mainly composed of valve seat, valve plate, spring and lift limiter. The lift height or closure between the valve plate and the valve seat determines the size and sealing of the gas passage. The spring is mainly used to push the valve to close, and it can also reduce the impact of the valve on the lift limiter when it is opened. The lift limiter can limit the lift of the valve plate and can bear the spring; the opening and closing of the valve plate is controlled by the gas pressure difference between the cylinder and the outside and the spring force, so no other drive mechanism is required, so it is called an automatic valve.