Exit the APC and head over to the stairs to the left. Walk up them, then go through the door ahead and follow the corridor round. Make your way through the next set of doors, then go round the room to get to the stairs on your right. Walk up them, follow the walkway round, then proceed through the next door and down the corridor. Walk up the stairs ahead, follow the ledge round, and go through the next door. From here, head right and through the doors at the end. Follow the ledge around to the left and proceed through the doors. Take the right-hand corridor and follow it round until you come to a large room with a fan in it. Walk up the stairs on your left, proceed along the walkway, and enter the control room at the end. Here, collect the Flamethrower in the corner and turn the wheel in the far left corner. Exit the room and fall to the floor (you won't lose any health). Continue down the corridor, going straight on and ignoring the door. When you come to the next room, walk right along the ledge you're currently on and fall down to the next level. Turn around, then turn the wheel in front of you. You need to be quick here - fall down onto the steps on the right, then run around to the top. A bridge is being lowered. When it gets low enough, jump onto it and run across to the other side, before entering the room in the corner. In here there are lots of bonuses. This is an excellent save point. Now exit the room, go across the bridge and keep on following the ledges round until you reach the lift. Ride it down, then enter the area on the right and take out the facehuggers present. Go through into the room at the end containing the pressure cylinders. Walk up the steps just to your right, then press "activate" to the wheel that's releasing steam. Now collect the Smartgun, exit the room and walk up to the bars on your left - they will now open. Go down the corridor, then take the first possible right. Walk onto the lift ahead and ride it up. Turn around and ride up the next lift, then follow the ledge along. In the next bit, follow the stairs up to the right. Go into the next area, then shoot the bar with all the flashing lights mounted on it. A walkway will fall down. Walk across it, then go through the doors at the end. Go down the stairs, then proceed through the room at the end to enter the Ventilation Control Room. Pull the two wheels to deactivate the two fans. Exit the room, go back up the stairs and across the walkway. Go round the corner and into the room on your left. Go down the steps - there's some Armour under the stairs in you need it. Walk round the corner and enter the room on your right - pull the wheel here to deactivate the fan. Collect the bonuses, then collect said room and go back up the stairs and out into the main corridor. Go straight ahead, ignoring all rooms and go right to the end. Here, head right and through the doors, then again keep following the corridor. You'll come to another room with a fan in it. Go up onto the ledge via the stairs and pull the wheel. Now leave the area and follow the corridor back around, through the doors and then left. Head right at the main intersection and go along the walkway, then through the doors with the green light above them. Go down this corridor, then walk along the bar on the right and enter the lift on the other side. Ride it up, then walk out onto the landing platform. The level ends when the dropship arrives