I went to a training class this morning called Fire and Smoke. The instructor was with the Illinois Fire Service Institute. He was great. It is amazing how some times the smoke will tell you whats going on, but other times it does not. You may have heard of the terms backdraft and flashover, but what about smoke explosion? A smoke explosion is when there are super heated gases at their ignition temperature, just waiting for an ignition source. These explosions are strong enough to blow firefighters off their feet. To see an example, check out this video clip. http://www.youtube.com/watch?v=aTQWNCeCBvQ
There was really no advance warning for this except for a couple of seconds before the explosion. It is very important to take time to assess the situation.