Don't keep onions in enclosed spaces?

[phan1]

I was wondering if anyone has heard of this, because I end up getting an awkward, sour smell when I do. I believe it's from the onions, but I'm not sure. The first time was when I was sous vide-ing meat with some whole green onions in. I open the bag, and I get a sour, unpleasant smell that's not meaty, so I guess it had to be from the green onions. The second time was when I was making fish stock with my pressure cooker, in which I included a big chunk of raw leek in there. When it hit full pressure, I smelled the same sour smell coming out of the steam. The vegetables were not spoiled or anything. Maybe the sulfur doesn't have a chance to cook away, and that's where the smell/taste comes from?

So I was just wondering if anyone has ever heard of this happening. Not often are we cooking things in tightly enclosed spaces anyway, so many people probably haven't gotten in a situation where this has happened. I'll be sure to cook out my onions before putting them in a pressure cooker...