What characteristics define Hydrogen Sulfide (H2S)?

Hydrogen Sulfide (H2S) is a colorless gas that is known for its distinct smell, which resembles that of rotten eggs. This characteristic odor is not just a notable feature; it also serves as a warning to indicate its presence, although it can be hazardous even at low concentrations. H2S is indeed toxic and can pose serious health risks, including respiratory issues and potentially fatal effects at higher concentrations. Understanding these properties is crucial for anyone working with or around this gas, particularly in wastewater management and treatment processes, where H2S can be generated.

Other characteristics listed in the options do not accurately describe H2S. It is not nontoxic, nor is it produced under aerobic conditions, which typically favor the absence of H2S generation. Additionally, H2S is flammable, contradicting the statement of it being non-flammable and odorless. Recognizing these distinctions is vital for ensuring safety and effectively managing wastewater treatment environments.