..self-igniting grease fire. Sort of the same idea - grease for, say, French fries is heated to the point of ignition. You blow it out with a few puffs but it continues to smoke sightly - then you pick up the frying pan to dump the grease down the drain and WHOOSH! - the smoke itself ignites in a flash fire. You can see smoke ignition in action with a candle - blow the candle out and while the gases above are still hot, put a flame in the smoke trail - candle magically re-ignites.
If you ever have a grease fire, blow it out and then LEAVE IT BE for 10 minutes.