[Thor]

You guys have to check this link out, especially the very bottom plans for the 80-90 man underground structure.

http://www.atlassurvivalshelters.com...bc/corrugated/

The mud room is a piece of 7' diameter pipe 10' long that attaches to the main living quarters. It serves several purposes.
1. It gives you an air-lock between the surface hatch and the interior door
2. If you have to spend a long time underground, it can serve as a trash room.
3. It serves as a shower room
4. It can serve as a temporary morgue if somebody dies
5. You can run a generator in there
6. You can store more materials in there
7. It allows you to walk into your shelter instead of crawling into your shelter.
8. It gives you a place for your dog to do their business if you can't go to the surface.