Hydrogen sulfide is a by-product of decayed organic material and is ubiquitously found as an ingredient of manufacturing reagents or as an undesirable by-product of the manufacturing or industrial processing. Hydrogen sulfide is a chemical asphyxiant and interferes with cytochrome oxidase and aerobic metabolism. It has thus been deemed an important cause of work-related sudden death. This gas is particularly insidious due to the unpredictability of its presence and concentration and its neurotoxicity at relatively low concentrations, causing olfactory nerve paralysis and loss of the warning odor. Here, we report two cases of comatose patients presenting after accidental exposure to hydrogen sulfide gas.