When finished cooking with the BBQ and cleaning the grill, I leave it running for a bit then shut off the intake and cap the exhaust (it's a Big Green Egg).

At this point the BBQ is essentially sealed and with temperature being above 300F everywhere inside, presumably sterile. It cools down naturally over time with practically air-tight conditions.

However, in a couple of weeks there is visible mold on the grill. The question is:

  • How can this happen?
  • Are others experiencing this, is it 'normal'?
  • How do you prevent it?

3 Answers 3


Mold is growing because there's something for it to consume, the only way to prevent it from happening is to clean your grill more effectively, or carbonize it before the fire goes out. No grill is air-tight, so even though it gets a good heat blast (not enough to sterilize it as you may think), spores will get in from outside. Remember, hot air is less dense, so as the BBQ cools it will draw air in, hence the spores. Once there they thrive in the sheltered and often damp conditions in a closed-up barbecue.

I think where you may be going wrong is that you close the valves after cooking. That cuts off the air and kills the fire. I leave all my valves open to keep it as hot as possible after I'm done cooking, and it does a better job of charring all the leftovers.


After the Big Green Egg is COMPLETELY cooled down, put a container of DampRid on the grate. We kept our BGE outside all winter and spring with the cover on it (and a 10 oz. container of DampRid sitting on the grate) and did not have any mold inside it when we opened it last week (June) for the first time since last summer. Last year we had a lot of mold inside it every time we used it.


It wasn't a cleaning issue the grill is spotless.

It takes a very long time to cool so it stays in the danger zone nearly forever and a little air coming in through the gates (Per GdD) will condensate on the grill making it ideal conditions for the mould.

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