Which gas is known as stink damp due to its characteristic smell?

Hydrogen sulfide is known as "stink damp" because of its distinct and unpleasant odor, often compared to that of rotten eggs. This characteristic smell is due to the presence of sulfur in the compound, which is highly recognizable even at very low concentrations. In mining environments, hydrogen sulfide can be a critical safety concern, as it's not only hazardous to health due to its toxicity but also because its odor can alert miners to its presence before it reaches dangerous levels. Recognizing the smell of hydrogen sulfide is crucial for miners to take necessary precautions to ensure their safety.

The other gases listed—methane, carbon monoxide, and ammonia—do not have the same immediate olfactory warning associated with them; for example, methane is odorless and typically requires an additive to give it a detectable odor, carbon monoxide is also odorless and highly poisonous, and ammonia has a sharp smell but does not carry the same common nomenclature associated with mining hazards. Therefore, hydrogen sulfide is rightly identified as the gas referred to as "stink damp."