Introduction
Often referred to as “pit gas”, hydrogen sulfide is a highly toxic gas.
It is naturally produced by decaying organic material in the absence of
oxygen and is a byproduct of many industrial processes. Its toxicity
most often occurs in occupational settings such as petroleum
refineries, commercial fishing holds, and pools of sewage sludge or
liquid manure. Fatalities often involve exposure to high concentrations
of hydrogen sulfide (>150 ppm) [1].
Hydrogen sulfide concentrations as low as 0.03 ppm can be easily
detected by its characteristic rotten egg odor. The recommended
workplace limit is 10 ppm for an 8‐hour work time average, with a
short term exposure limit of 15 ppm [1]. Respiratory tract irritation
occurs between 50‐100 ppm. Olfactory nerve paralysis, causing a loss
of ability to smell the characteristic odor, occurs between 100‐150
ppm. Pulmonary edema occurs within 300‐500 ppm; levels of 600‐800
ppm are promptly fatal [2].
Hydrogen sulfide causes its effects through inhibition of the
cytochrome oxidase system and cellular respiration. Clinical
presentation of hydrogen sulfide toxicity includes headache, nausea
and vomiting. High dose exposure may result in unconsciousness,