Oh, I've got the old grating from the top of my reptile tank over half the bin, so he's getting plenty of air (never actually had reptiles, used the grating in S.D. in the summer when the heat in the room made it necessary to not have a lid on my tropical fish tank because the water got too warm). He would definitely squeeze between the oven rack rows, easy. They are escape artists. Fortunately, they can't really jump, and the bin lid is well higher than his abilities. And the inside of the bin is straight up/down walls with no lips or ledges, so he's good. As time permits I will go get some window screening, and cut around the interior of the lid, and then duct-tape the screen down so the entire top of the bin is air-permeable. But not to worry, he's in no danger of suffocation as it is. And he has lots of room now and has been entertaining himself with burrowing in the bedding.
I'm afraid I just spent a ridiculous amount of money on hamster supplies, and he's not even mine.

Ok, he's terminally cute and I'm a pushover for little button eyes and twitchy whiskers. And pretty brave for a hamster. Will figure out how to get a photo taken and post it as soon as I can.