Shadow:
i have a question would it be possible to shut the air off in the bunker?
You could find and plug up the air intakes on the bunker.
To survive a nuke strike the bunker would have to have a life support system of some sort so it could last some time cut off. It would be on the order of days - weeks depending on the system and amount of people.
It is also possible the bunker has wiring going to the base computers or communications gear. Certainly would have some surface condition sensors to tell those inside if it was safe to come out.