Daffy,

Read your whole quote again. They were "taking" bets not "making" bets. That means they were sure they weren't going to ignite the whole atmosphere. They alll had enough background in pryotechnics to know that the amount of atmosphere was too great to be ignited by those firecrackers. The atmosphere is not as volatile as the natural gas in a residence that, once left leaking with the windows closed will ignite with one flip of a light switch.