According to both the text file and the Requiem info pack:
Just one of the many bases that has [sic] fallen to the demonic attack, this was once a research and development centre for the UAC, investigating the uses and processing of various non-toxic chemicals recovered from Mars and her moons. Many areas of the base are cluttered with the shielded piping used for the chemicals : this may make progress treacherous, so watch your step. Be on the look out for signs of concealed equipment bays, there are sure to be several scattered across the base.
The teleport pad that you start on is animated, unlike the others in the same room. Push on the wall behind it to find security armor. (sector 201)
In the green hallway immediately after the first room, the pipe running along the south side has sprung a leak at the southeast. The wall behind it can be opened, leading to a stimpack and a box of shells. (sector 156)
In the brown room southeast of the green hall, a portion of the east wall has ridges on its bottom end instead of the top. This can also be opened to reveal two stimpacks, two sets of shells, and two rockets. (sector 173) Opening the wall will also open a doorway from this secret into the green hall.
In the passageway around the yellow key, two of the tiles at the south end are brown instead of gray. Press on the wall behind them to find a backpack. (sector 178)
Once you get to the northeast of the room after the yellow key-locked door, look southeast to find grating in the floor. Push on the wall behind it, and a passage will lower, allowing access to a medikit and a box of ammo on the other side of the railing. (sector 223)
In the exit room, the lamp housing in the northeast is missing a lamp. Push on it, and the east wall will open to reveal a medikit and a box of shells. (sector 326)
In multiplayer, all players will be restricted to the first area of the level, with the yellow key door blocked off by a wall that is raised when you leave the start room. However, this area does not contain an exit, preventing you from leaving the level in multiplayer gameplay unless a timer has been set through the -timer switch. The Deathmatch Repair File created by Steve Terry adds an exit to this area located in the central pipe in the east of the level. In single-player gameplay, this switch will be closed off when you leave the start room, allowing the level to be completed in the intended fashion.