Much of the area is comprised of tile floors and concrete walls. The doors and trim are made of red metal. Offices have carpeted floors and brush desks with wood tops. Several parts of the chapter require the player to climb through air ducts to get around obstacles, such as the beginning where the player has to climb into a duct to get around a locked door. You can use these ducts to lead players to hidden objects of interest, like ammunition or suit batteries.
Several offices are trashed much like the earlier parts of the game, such as the flooded one near the beginning. To add variety, leave some mostly intact. Vending machines and trash cans are also found occasionally, namely in communal areas around offices. Consider placing diplomas and whiteboards on office walls and couches and bookshelves in resting areas to increase visual interest.
As seen in
c1a2c the sector does have some more industrial areas, such as the freezer area. You should put down a few icy patches where the player could unwittingly stumble into enemies.
Scientists and security guards should be common. Placing security around areas with multiple enemies should be done to give players some extra firepower. Scientists can sometimes be seen being dragged into air ducts and ceiling tiles by unseen aliens. Dead scientists are also a good idea when done conservatively.
Aliens should include headcrabs (usually falling out of the ceiling), zombies (often seen eating dead scientists), bullsquids (primarily in the more industrial areas), and Vortigaunts. Vortigaunts are usually seen in groups of three, whereas headcrabs are usually in groups of two or three, though possibly more.