See I think this was a combination of airborne dust and a really hot firebox from having the ash door open and poking up through the grate to dislodge clinkers and the related ash. The coal bed had been nice and red for awhile, I loaded it up about an hour before. This wasn't a blue flame rush, I do get those sometimes when I open the door to check on a new load. This was a dust laden yellow flame explosion with very little compression so other than the woosh there wasn't any sound. Came out much faster than the blue flame rush that I get sometimes right after I fill the stove and I always leave a some hot coals uncovered when I load. I normally sprinkle the back half, get them going, add some more and then wait awhile before filling the front half.