The gas chamber is usually a small chamber, which is made air-tight with a door (typically with rubber strips around) into which the prisoner is escorted and either placed or fastened to a chair with straps, and left inside. After this, the gas is inserted either through a hose or a pellet is dropped into a solution which combined produces deadly gas, and the person(s) is asphyxiated within minutes. In the United States, one or two people maximum were executed at a time, although recently it has become extremely uncommon. After California stopped using it in favour of lethal injection, it became nearly redundant. But it is still possible in several states, typically as a second method, in case there would not be drugs for an injection to be performed, or if the prisoner prefers to be executed by gas for any reason.