What Temperatures Kill In An Incubator? http://metzerfarms.blogspot.com/2011/08/what-temperatures-kill-in-incubator.html
High temperatures in an incubator are an entirely different matter. Injury or death depends on how hot it gets and how long it is hot. Hot temperatures for brief periods usually cause no problem. But sustained higher temperatures allow the entire interior of the egg to become hot and that is when injury and death occurs. And if it is an older embryo, it is generating heat and this makes overheating even quicker.
There are no black and white limits with overheating. Years ago I lost all the eggs in an incubator when it was 105 degrees for six hours. But on another occasion, I had no losses when the incubator was 102 for four hours. An interior temperature of 103 almost guarantees death.
What To Do When You Discover Your Hot Incubator
Immediately cool the eggs with water. If you have lots of eggs, spray with a garden sprayer or hose. If you have just a few eggs, dunk each egg in cool, not cold, water. Blow air over the eggs to more quickly cool them. Each time the egg dries, wet it again. Remember that as you cool the eggs, the shell will cool faster than the interior - but it is the embryo in the interior that must be cooled. Therefore, you want to cool the shell lower than the ideal temperature. And as I described above, don't be afraid of cooling them too much as temperatures below ideal will not be a problem.
If you have an infrared thermometer, I would cool the shell to 80-85 degrees. If you do not have a thermometer, hold it against your eye lid. Once it feels slightly cool, put it back in the incubator and turn it on (assuming you have fixed the problem in your incubator!).