This is the area used by the player to get to the upper section of the spacecraft, following the destruction of the three generators. The entrance to it is next to the work bench of the engineering core and will be locked until all three generators have been blown up. There is a large button in the middle of the room that starts decompression. Note that the astronaut's spacesuit must be worn before depressurization to avoid explosive-decompression and the death of the player. Dead alien bodies may be found scattered around after leaving the first chamber (presumably killed by the depressurisation process). The decompression chamber acts as an airlock between the spaceship and the space environment to lessen the strong vacuum effects when the air pressure disperses into space, and is a relatively small area compared to some of the other areas on the spaceship.
Note that the decompression chamber (and by extension, the space walk) is a one-way trip. The player cannot return to the airlock after leaving it and must use the transporter to reach the upper level of the ship, completing the Among the Stars quest.
Failing to put on the spacesuit, or removing it after decompression, will cause the player's head to explode.
Note that although the air in the decompression chamber should be gone, the flamer still works. The flamer fuel may contain oxygen, however, accounting for the science-defying flame.