There shouldn't be any smell from a broody unless she's accidentally pooped on the nest or an egg is rotten. Or there's something wrong with the poor hen.
Trust me when I say, plenty of folks on here have full-time jobs and eggs get left in the nest box all day! Most of the time there's very little chance an egg-eater will develop because an egg was left in the box. They probably won't go broody because of it, and the egg won't spoil in the heat...