Hydrogen Disulfide is deadly, one or two wiffs and its game over
I discovered that also after doing some Googling. The good news it that it VERY RARELY occurs in sufficient quantities to be lethal. The same "rotten egg" stuff we made in chemistry class in high school to annoy the teacher. The question I never pursued is what is this stuff doing there. H2S is a by-product of many sour oil and gas wells but I wonder why they capture the stuff instead of releasing it into the atmosphere. Outside of the smell, the effects in the quantities involved most likely would be negligible. I have to assume some nanny state regulations.