Known as a Backdraft to fire fighters, It is caused by the rapid burning of Volatile Organic Compounds (VOC). It will most likely occur when you have that thick white smoke bellowing from your egg after you light it and you dampen down your egg. You could experience puffs of smoke and flame out the bottom vent Be real careful when you open your egg during these conditions. If you open the egg too fast that VOCs built up in the dome will ignite and roll out at you in a very pretty blue flame. You will be missing a LOT of hair (arms, eyebrows, head) in a really short time. I recommend you take the Metal top off and open the egg no more than an inch with some sort of heat resistant gloves on. This will contain the flashback sending it out the top and away from you. Now if this is happening with the food on it usually means you did not give the egg enough time to burn all this off ahead of time. Allow the smoke to clear before cooking. The Naked Whiz has a very nice flashback video demo of this effect. You should watch it. Now go forth grasshopper and cook good food safely. good eats. ...have fun. ..