Thiols (or mercaptans, an older term) are a group of chemical compounds with structural similarity to alcohols, e.g., ethanethiol (C2H5SH) resembles ethanol (C2H5OH). Some thiols are used as warning gases. Their strong and repulsive odor can warn users of an explosive gas that is leaking into the air. [Hawley] See Benzenethiol, n-butyl mercaptan, methanethiol, ethanethiol and other thiols in this database. The thiols with higher vapor pressures can be acutely toxic in spill accidents causing respiratory irritation, coma, and death. The thiols can, like hydrogen sulfide, produce CNS injury and respiratory paralysis. [ACGIH] See Methyl mercaptan, Benzenethiol (Phenyl mercaptan), and 2-Methyl-2-heptanethiol all classified as TIH (Toxic Inhalation Hazard). [ERG 2016].