Air lock

Air lock, mechanism that allows people to pass between areas of different atmospheric pressures. The air lock chamber has 2 airtight doors sandwiched between the 2 pressure regions. The atmosphere in the air lock is gradually adjusted to match the pressure of the next space to be entered. Air locks are used when transferring people between the outside air and compressed air spaces such as underground tunnels and pneumatic caissons (watertight chambers) and between space vehicles in outer space.

See also: Bends.