What does a rotten egg odor indicate?

A rotten egg odor is primarily caused by hydrogen sulfide, a colorless gas with a characteristic smell that resembles that of rotten eggs. This gas is often produced by the decomposition of organic matter in stagnant water or in environments with low oxygen, such as sewers or landfills. In the context of forensic investigation, recognizing this odor can be significant, as it may indicate the presence of decomposing biological materials or specific chemical reactions occurring at the crime scene.

In contrast, aromatic hydrocarbons typically have sweet or pungent odors, ammonia has a sharp, irritating smell, and chlorine gas has a strong, bleach-like smell. These substances do not produce the distinctive rotten egg odor associated with hydrogen sulfide, which is critical for identifying this particular gas in various environments you may encounter in crime scene investigations.