So it is not normal during hatch. But what about after hatch?
Just got done with my first hatch and after a few of my chicks hatched I noticed it was getting a little stinky inside the incubator, but being a newbie I thought that it must be normal. By the time my chicks were dry the incubator stunk the whole room up. I had 4 eggs that didn't hatch, but I never opened them up to see what happened inside.
It doesn't smell like rot. It smells kinda like warm chicken poop. I think it must be normal but strong because I'm having a three day hatch. Woke up this am to three more out and two more zipped.