His condition is genetic. My father in law was knocked on his butt by an explosion while starting a bon fire... with gasoline. My brother in law lost most of his arm hair and part of an eyebrow burning who knows what in a chimnea. I witnessed that one. The flames shot a few feet out of the top spout.
Because my husband uses our fireplace so often (to feed his habit), it had gotten pretty grungy.
I read the best way to clean the brick around your fireplace was with cola. Seriously? The instructions were to soak the brick with cola and use a stiff brush dipped in hot water to scrub the area. I filled a spray bottle with old Pepsi and had at it.
It worked ridiculously well. I was absolutely shocked. Who knew?