Hydrogen Sulfide (H2S) is a colorless, highly flammable, and toxic gas with a characteristic rotten egg odor detectable at very low concentrations (0.01-1.5 ppm). It is produced naturally in sewers, swamps, and oil fields and is used in chemical synthesis and as a reducing agent in industrial processes. H2S is extremely hazardous, causing severe respiratory irritation and potentially fatal effects at concentrations as low as 100 ppm. Its flammability poses fire and explosion risks, and it is typically stored as a compressed gas in specialized cylinders. Strict safety measures, including ventilation and gas detection systems, are essential during handling to prevent exposure and accidents.