The Airlock Module (AM) connects the Orbital Workshop to the Multiple Docking Adapter. It had hatches at both ends to allow crew to move between docked craft and the Workshop in a pressurised environment. With the hatches closed the airlock can be de-pressurised to allow EVA's through a side hatch. The EVA hatch on the Airlock Module was based on the hatches used on Gemini spacecraft; including a window.

The Airlock Module weighs 22,050 Kg (Loaded), a 3m diameter, is 5.1m long and has a habitable volume of 17.4 m³.

The Airlock Module has three main components:-
1. Aft connector - A flexible tube connecting the module to the Orbital Workshop,
2. Central Tunnel - Has three compartments with hatches between them. Only the central (Lock Compartment) can be de-pressurised.
3. Forward Structural Transition Section (STS) - Connects the Central Tunnel to the Multiple Docking Adapter. It has a larger diameter than the Airlock to transition to the Docking Adapter. The STS contains four optical windows, storage compartments and various control panels.

Fixed Airlock Shroud (FAS)

A Fixed Airlock Shroud (FAS) surrounds the Airlock Module forward of the Saturn Instrument Unit with the same outer diameter. The Airlock Module Central tube has a smaller diameter, leaving a space between the FAS outer shell and the Airlock Module. This space contains six large high pressure oxygen tanks, six nitrogen tanks, battery banks, and other station equipment. It also contains a lattice of structural elements to support the Apollo Telescope Mount.