Over my years here I've commented in response to others my thoughts on controlling flashbacks with the Egg and I've never experienced any, at any temperature, since I've used this simple visual clue, so I thought I'd use a new subject line to run it by you all. If someone else has offered this up already, I apologize for repeating it......
Basically, the fire is like a human in that it survives on the air it gets. Give it air by opening vents, it gets larger and healthier, reduce or remove and it starves and dies. Easy enough to understand. With the flashback it occurs when the fire 'breathes in' a big gulp of air as you open the upper lid, which causes quick combustion and results in a big 'belch' of fire back at you.
My 'theory' is that you should open the dome lid an inch, look down and see if any smoke or steam vapor is coming out. If it is, you are good to go on continuing to open the lid flashback-free. If it isn't, lower lid/open vent etc (the usual 'burp' method) and try again. Basically, to carry the human breathing analogy back to the Egg, if you see smoke curling out it means the Egg is currently in exhale mode. If it's breathing 'out' to emit that smoke, it's incapable of breathing in (the big air gulp) at same time, therefore no belching flashback.
There are a whack of guys on this forum with more technical knowledge of combustion etc, but this visual clue of exhaled smoke has never failed me yet. Have I just been lucky these last few years or can we safely say that:
"If smoke's coming out, no flashback's about"??