This is an air vent for steam. As a valve that removes the air that remains within the steam system or the non-condensable gas, it prevents the heat conduction from becoming uneven due to disruption in the air flow, as well as slowing down the corrosion of the pipes. The valve closes with a temperature change in the steam. Once air or non-condensable gas flows in, the temperature falls, triggering the valve to open to let the air or non-condensable gas out. The degree to which the metal bends and the force applied varies according to the pressure in the steam line used. This helps with the sealing effect and an extended useful life of the product.