It's very small and is focused on two things (explained in description). Map consists of 4 rooms and corridors between them (excluding 8 ways for zeds to come, 4 of which are behind the doors). Thanks DoctorEvil for testing.
1) The smoke.
At any moment there is only one room that is not filled with smoke. Every few minutes it switches to one of the 2 closest rooms. 10 seconds before smoke will start appearing, yellow strobe lights turn on.
Red lamp above one of the exits will turn green, that's a sign that corresponding room is clear now.
The smoke is very thick, and if you will not move, you will be at a huge disadvantage.
When boss spawns, all smoke is removed.
2) Welding is... Well, from what I've seen, it is extremely useful. Each room has 3 ways for zeds to approach, and if you will weld the door, it will turn into only 2.
First, the doors have around 2 billions health. I'm not sure if it's possible to exhaust all that health in a single game without intention.
Second, its maximum "weld" hp is 2500 instead of regular 1500.
There are only 4 doors, and if zeds (or players) will break one, it's gone forever, so try to unweld them before you move to the other room.
I've added air shafts above all doors so you can nade things on the other side, just destroy its cover with your gun. On BOTH sides, preferably.
Using air shafts you can kill almost all trash behind the door before unwelding it, it's pretty consistent. Scrakes and fleshpounds do not spawn there.