All one needs to breach an underground bunker is to find the fresh air source, and park a vehicle with hose attached to the exhaust over it.
I never understood the underground bunker thing. I guess if you want to get really sophisticated, you could build an re-breather, and shut off all outside air.
I never understood the underground bunker thing. I guess if you want to get really sophisticated, you could build an re-breather, and shut off all outside air.