Stone walls and metal fixtures are common here. The facility is meant for low-level industrial use, and is therefore spartan. Pipelines aren't hidden in the walls; they're located in plain sight. Hallways tend not to be tall, whereas rooms are very tall and open. Bridges and catwalks are generally placed high up.
The facility should be in disuse but not disrepair. Machinery should still mostly work, despite its age. Some of the larger rooms are flooded with toxic waste. Explosives are also occasionally stored in the complex, which can be placed around bullsquid to aid the player in dispatching them.
The original function of the labs was as a rocket engine testing site. The main goal of Blast Pit is to activate the fuel, oxygen and power lines in order to fire the engine and burn up the tentacles. If making a custom map in these labs, consider having some lines on and others off.
While other aliens can be spread around for variety, Blast Pit centers around one major alien, monster_tentacle. There are three in the chapter placed in the same lab, and they attack by smashing the player. While scientists and security guards can be found deeper in the facility, it's best not to place them in groups since the silo complex has long been deserted. HECU squads should not be found here.