Final answer:
Low doses of hydrogen sulfide smell like rotten eggs. This chemical is dangerously toxic and can numb the sense of smell, making its presence undetectable after exposure. Other sulfur compounds also exhibit strong odors.
Step-by-step explanation:
Low doses of hydrogen sulfide, H2S, typically smell like rotten eggs. Hydrogen sulfide is a colorless gas known for its offensive odor, which is often associated with rotten eggs and some hot springs. Even though it has a distinctively foul odor at lower concentrations, hydrogen sulfide can be very dangerous. It is as toxic as hydrogen cyanide and can quickly paralyze the olfactory nerves, leading to an inability to detect its presence after just a short exposure. Thus, the smell of rotten eggs from hydrogen sulfide may suddenly disappear, not because the gas is gone but because the sense of smell has been compromised.
Besides hydrogen sulfide, other compounds with sulfur, like thiols found in foods such as oysters and onions, also have strong and often unpleasant odors. These include methanethiol and prop-2-ene-1-thiol. In the broader context, a variety of chemicals, including butyric acid found in body odor and certain amines released by decaying fish, contribute to a range of characteristic, and sometimes offensive, smells.