i usualy give them 5 minutes. last feed i had 2 rat pups and one small rat. i had very thick fog in there for at least 5-7 minutes. i let it air out another 5 minutes. all the rats were way dead, but 10 minutes later whil roo was eating one of the rat pups started breathing again, and i could see it's little heart beating again. i quikly fed this little one to roo before it actualy woke up. make sure you feed them to your snake as soon as the fog clears. this is the only time i had trouble with a rat waking up so far though. using 2 cups of fog instead of one next time.