Wouldn't it take a lot Lot more exposure to be dangerous? It's an irritant at a low level, maybe more so for asthmatics. But I would think dangerous levels would be hard to reach.
It depends. Niosh and OSHA set different limits - as low as 10 PPM for a ceiling limit. Hydrogen sulfide is also called sewer gas and happens from bacterial breakdown of waste. If the stuff sat for a month then I can only guess of the amount in PPM once released. I don't know that answer. It acts kind of like carbon monoxide in that it affects the ability to exchange O2 at the cellular level - "displaces the oxygen". That can happen in as little as 20-50PPM per million, especially in someone with health problems or children. At high enough level it will paralyze the olfactory nerves so you won't smell but a little bit right off the bat and then nothing, but it won't matter because you would soon be unconscious and/or dead.
I can only guess at the amount that is produced in the regular size of a bio-pellet reactor. It is feasible that sticking your head in the opening and inhaling isn't the brightest thing to do and cold be enough to produce a short term amount that will cause irreversible damage. It's kind of like sticking your fingers in something you don't know what it is and then licking them. We use our senses too much.
John
"Critics are men who watch a battle from a high place and then come down and shoot the survivors." Ernest Hemingway