Part 14

Crouch-walk back into the shaft after climbing up the unbreakable grating.

Approach the next opening on the right slowly with your pistol and flashlight to sneak-shoot the headcrab.

Go down the shaft and observe the two marines below through the unbreakable grating. You can likely ignore them and gather ammo from the room past the end of the shaft.

If you need to engage the marines, shoot the red-beret marine with a double-barrel shotgun blast through the nearest floor grate, then shoot the other marine with the assault rifle through the same grate when he is in sight.

Return to the main vent shaft, turn right, and find a left branch leading to a room with a first aid station, two armor batteries, and assault rifle clips.

Jump onto the green crates under the unbreakable vent grating and use it to climb back into the shaft.

Go back to the fan room, move along the narrow ledge to drop to another narrow ledge, and enter its adjoining vent shaft to briefly return to section c1a3d.

Proceed to the end of the shaft to find a ledge with shotgun ammo, then climb back into the shaft and return to the fan room.

Drop to the floor and enter the shaft opening below.

At the end of the long shaft, climb the ladder and get off on the lower of two small platforms.

Use its vent shaft to reach the silo door control room.

Press the big red button to open the silo door, pick up the shotgun ammo, and exit the control room.

Use the nearby first aid and HEV (Hazardous Environment suit) stations if needed, then go through the silo door to begin the "Blast Pit" chapter.

Go to the left end of the big barricade and shoot the bullsquid in the distance with your pistol.

Use your crowbar to bash away the barricade material.

Shoot the two headcrabs among the boxes past the barricade.

Move through the big doorway, watching for another headcrab to your right.

Go up the ramp to the small control booth and move slowly toward the metal door.

Back off quickly when you hear the zombie hitting the door to avoid being seen.

Toss a grenade through the doorway unseen and back up before it detonates the explosives, killing the zombie.

Check the room for grenades and a health pack.

Use the lever on the control booth's panel to bring up a big lift.

Use the ladder to climb down to the lower-floor area and get on the lift.

Use the lift's button panel to start it, then turn around to face the opposite way.

As soon as the lift stops, move onto the walkway with health packs, turn right, and drop to the tracks next to the rail car.

Whack the houndeyes that approach with your crowbar or shoot them with the shotgun.

Jump onto the rail car and press against its control panel.

Press the "Use item" key to bring up the speed display, then press the "Move forward" key several times to reach top speed.

Crouch down next to the control panel to avoid bullsquid spit.

When the speed display disappears, stand up and look ahead.

As the car starts crashing through wooden warning markers, quickly back off to avoid being thrown off.

As soon as you hit the ground, run toward the car.

Jump-crouch back onto the car when it has stopped, then get on the two small side beams on its right and jump-crouch onto the ledge.

Crouch-walk along the narrow part of the ledge to reach a wider part that allows you to cross the room without touching the toxic water.

Find a spot partway across where you can shoot the bullsquid on the other side, but it cannot spit at you due to a large pipe.

Go to the end of the ledge and drop down to the floor.

Crouch-walk under a huge pipe, then climb the ladder on its other side.

Get onto the top of the pipe and carefully make your way along to a smaller side pipe with an open hatch.

Drop down into that pipe and move along it until section c1a4k loads.