All ships should have a large, dangerous airlock. Good for a variety of uses from loading and unloading cargo to cleaning out dust bunnies from those hard to reach areas.
A closed airlock counts as empty space for all purposes. An open airlock is, well, an open airlock. Ending movement on an open airlock square turns the character into an instant space walker.
Each phase an airlock is open forces characters in LOS to the fan to make an Athletics check vs 8 to avoid being sucked towards the airlock. The presence of each fan module on board will increase this check by one up to a maximum check of 11. The amount by of success determines how far the character can move. Failure indicates how many squares the character moves towards the airlock.
Open AirLock (Engineering skill vs 8) Opens the airlock. If this is done locally, the character taking this action avoids all penalties as long as they stay at the station (they strap in to avoid the suction.) The airlock does not actually open until the Grenade Detonation phase.
Close AirLock (Engineering skill vs 8) Closes the airlock, canceling all effects from it being open. Unlike opening, closing happens immediately.