I did once do a project in an aircraft maintenance hanger. We were told it would fill with 6 feet of foam in 10 seconds if the system triggered. Felt it best not to investigate the accuracy of the statement.
OTOH those CGI'ed endless corridors of servers you see in teevee commercials, you gotta be a real fast runner. On the gripping hand, the only way to power a place like that is to put it right on top of a nuclear power plant, so if there's a fire there... hypoxia might the better alternative.