Examples from the Web for air valve
If now the air-valve be opened very slightly, an internal cone of the same blue colour makes its appearance.
He stopped the engines, opened the air-valve, and the great ship instantly began to settle quietly down.With Airship and Submarine|Harry Collingwood
The professor opened the air-valve and the ship at once began to settle down.The Log of the Flying Fish|Harry Collingwood
It was the kind of door that shuts with an air-valve, and it closed gradually, tranquilly, like velvet; a perfect lady of a door.Life's Minor Collisions|Frances Warner