So I'm picturing moments like the LAPD Commission meeting today, the people so determined to riot that the commission left the room until they calmed down. (That's the way to do it; no peace, no 'Justice.') It that didn't work, if the mob decides to rush the the podium, etc., (And they did after the decision was announced) someone pulls out their quite impressive looking Tom Swift Electric Assault Weapon and takes a warning shot at some preinstalled, oh, balloon filled with hydrogen. Quite a bang to go with the flame. If that doesn't work, the whatever methanol solution he mentioned could be spread on the wall in advance. Maybe a second with some of that gunpowder in it will work if the first doesn't.
Think of it all as demotivational training for bad guys. And that's what out of control heroes like Tom Swift are all about.