Here we go, then.

Search around the level you start on - and the level above - for health, flares and translator messages (on the lower level, there's a switch in the black alcove that activates a lift down...).

Find the opening by the door on the upper level and follow the green-lit vent until you come to the wrecked control room. Drop to the lower level, turn around and go through the door - the kevlar armour in here can be released by nutting the switch on the ceiling.

Head back to the control room and drop to the lowest level, and go through the door. Carry on to the medlab, enter the door, go through the fan room and proceed until you find the half open door... hear the screams, see the blood hit the floor and catch your first glimpse of a Skaarj.

Enter the room, grab the dispersion pistol, and carry on to the room with the two huge wall-mounted fans. Walk through the disused one and, in the room beyond, press the handle in the wall and wait for the lift.