Getting to the Yellow Key Slot (2)

Go through the forcefield in the hallway that you opened. You will encounter some resistance from newly spawned enemies.

In this room, you will be attacked by an Enforcer and a Trooper. To your left and right are Slimer Eggs; you should dispose of them. Take caution to the right, as there is a babe there.

In the armory, you can find an RPG, Chaingun Cannon Ammo, and a box of Shotgun Shells. To the left, there are more Slimer Eggs and a Small Medikit, and Pistol Ammo.

To the right, there is Pistol Ammo and a Sentry Drone near the end, as well as a Yellow Key door.

Go to the left and into the door. There is a small path that ends with an impenetrable door and the Yellow Key.

Go into the Yellow Key door. In this door, there are two Enforcers and a Mounted Gun, so use a Pipebomb.

Inside, you will find more Pipebombs and a Pistol.

You will notice a switch; shoot it with your pistol.