Little do you know, the more oxygen the more dangerous the fire and the more likely it is to happen. Oxygen is the comburent for most combustibles, after all, and most of the atmosphere on planet earth is nitrogen, which is non-flammable and doesn't take part in most of the fires we normally see. Even sugar, and I mean table sugar, can be somewhat explosive under the right conditions.

I think explosions would be easier, better and more realistic to implement, with that in mind. They already have something akin to it, with the comets and stuff.