A news item from the recent tornado devastation in Moore, Oklahoma:
http://situationroom.blogs.cnn.com/2013/05/22/22-people-survived-in-bank-vault/?hpt=hp_t2
22 people survived by sheltering inside a bank vault. I don’t know much about modern vaults. Is it even possible to throw the bolts from the inside? If not, it seems possible the winds could pull the door open. Obviously (I think) you would not want or need to lock it, just keep it closed.
Assuming a loss of power, the ventilator fan would become ineffective (and the lights would fail). But there’s really more air available than commonly thought, more than enough for the few minutes the tornado stays in the general vicinity. A potential pitfall is that debris could have blocked the door from opening.
Below are images of the Moore credit union:
Below is a striking image from the Joplin tornado of 2011:
