Is there such a thing as overloading an incubator?

[ktblue3]

Have a Hovabator Genesis 1588 with the egg turner. It can hold around 40 eggs but I've never put that many in. I looked on the site for information about how many eggs are best to be in an incubator that size. Wouldn't there be an issue with not enough oxygen (even with the plug open?)
K........