It reminds me of the hydrogen lab I saw at a university once (my alma mater did not have one): it was a single-room structure made of reinforced concrete, about three stories tall, adjacent to the main chemistry building. The roof consisted of very lightweight panels (not sure how they kept it leak-proof from rain and snow). The idea was that if you were in there conducting experiments with hydrogen and blew yourself up, you wouldn't take the rest of the chemistry department with you: the explosion would go straight up, blow out the ceiling, and create a huge roman candle. There were also serious ventilation systems to help prevent an explosion in the first place, but just in case the whole thing was a giant chimney.