This is probably a dumb question, but I have a Day 9 egg that I'm sure has nothing growing. I'd like to break it to see what's going on inside but I'm wondering if it will stink. (I'll probably still break it--but I'll do it outside.)
If it looks clear when you candle it, meaning no dark blob at all, as the embryo would be about the size of a quarter on day 9, you can crack it outside. (I would leave it till day 14 if this is your fist time) As long as there are no fractures in the shell to allow bacteria inside, it shouldn't smell much more than a warm egg. However, any bacteria inside that egg and it will smell to high heaven.
It also depends on how long it's been dead. I had a couple dead-in-shell ducklings after my last hatch. Two were well developed and had probably been dead less than five days. They smelled like nothing much. The other was only about half developed, and it stunk to high heaven. Still, once I disposed of it (in the woods!!) and rinsed out the sink, the smell went away pretty quick. Oh, also, if it's *really* bad, it will stink even before you open it. So, stick your nose right up on it and sniff--if you smell nothing or just a clean smell, you're probably not too bad off. Good luck--opening them is always very interesting. It freaked me out the first time, but once I'd done it once it was no big deal to open the rest.
If it really is clear, it will not smell any different than a fresh egg. I have left peafowl eggs in the incubator for 30 days before breaking them open. They were clear (infertile, actually) and even after a month, they didn't smell. ETA: if it's a real "stinker," you'll see grey blobs floating around when you candle.
