I think if there is severe fire damage done by an explosive or long-standing fire, it should create an environment that causes passive damage when moving through it until it repaired/cleared/etc.
I'm thinking similar to the cut you get when you jump off a roof or something.
This would give a little extra weight to explosives, and more of a reason to get them cleared out by the powers that be, which would result in more work for the 3LP level folks.