How explosive is hydrogen on its own? Eg if I light a match to a hydrogen leak in air, how bad would it be? I thought it would just burn, without a pure oxygen counterpart. So comparable to petrol.
So at least 15 10-year-old-bathroom-minutes explosive. In short, very loud. But if they do it repeatedly in front of a hundred children, probably not too much. I don't remember feeling any pressure wave.
But I'm guessing that a hydrogen leak in an enclosed space could easily result in a dangerous H2/O2 mixture.
I guess the "enclosed spaces" case matters for eg underground parking, maybe less in roads.
[1] Health and safety wasn't much of a concern back then. I also remember another lesson where we lined up and plunged our fingers into a beaker of mercury. Quite a weird feeling.