H2S (Hydrogen Sulfide) Poisoning

Anywhere air circulation is slow there is the need of a mechanical aid to guarantee the health of workers

I was watching “Mystery at Blind Frog Ranch” on Discovery (Season 2 Episode 8 – “Darkness, Danger and Death”) when they encounter H2S in a tunnel that they found. I wanted to do some research on the deadly gas and learn more.

Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in an ambient atmosphere having a characteristic foul odor of rotten eggs. It is well absorbed through the lungs while skin absorption is minimal. Exposure by any route can cause systemic effects.

However, although its strong odor is readily identified, olfactory fatigue occurs at high concentrations and at continuous low concentrations. For this reason, the odor is not a reliable indicator of hydrogen sulfide’s presence and may not provide an adequate warning of hazardous concentrations.

Hydrogen sulfide is slightly heavier than air and may accumulate in enclosed, poorly ventilated, and low-lying areas. Prolonged exposure to hydrogen sulfide, even at relatively low levels, may result in painful dermatitis and burning eyes. Direct contact with the liquefied gas can cause frostbite. Hydrogen sulfide is produced naturally by decaying organic matter and is released from sewage sludge, liquid manure, sulfur hot springs, and natural gas. It is a by-product of many industrial processes including petroleum refining, tanning, mining, wood- pulp processing, rayon manufacturing, sugar-beet processing, and hot-asphalt paving. Hydrogen sulfide is used to produce elemental sulfur, sulfuric acid, and heavy water for nuclear reactors. Victims exposed only to hydrogen sulfide gas do not pose substantial risks of secondary contamination to personnel outside the Hot Zone.

However, personnel could be secondarily contaminated by contacting or breathing vapors from clothing heavily soaked with hydrogen sulfide-containing solution. There is no proven antidote for hydrogen sulfide poisoning. Treatment generally consists of support of respiratory and cardiovascular functions. Hydrogen sulfide is an extremely rapidly acting highly toxic gas.

Fatalities have occurred to rescuers entering the hot zone. Victims who are able may assist with their own decontamination. Remove and double-bag contaminated clothing. Handle frostbitten skin and eyes with caution. Wrap the affected part gently in blankets. Let the circulation reestablish itself naturally.

Encourage the victim to exercise the affected part while it is being warmed. Flush exposed skin and hair with water for 3 to 5 minutes. Use caution to avoid hypothermia when decontaminating children or the elderly. Use blankets or warmers when appropriate. Do not irrigate frostbitten eyes.

Otherwise, irrigate exposed or irritated eyes with plain water or saline for at least 5 minutes. Eye irrigation may be carried out simultaneously with other basic care and transport. Remove contact lenses if easily removable without additional trauma to the eye. If a corrosive material is suspected or if pain or injury is evident, continue irrigation while transferring the victim to the support zone.

Physical Properties
  • Molecular weight: 34.1 daltons
  • Vapor pressure: >760 mm Hg at 68°F (20°C)
  • Boiling point (760 mm Hg): -77°F (-60.3°C)
  • Gas density: 1.2 (air = 1)
  • Water solubility: Slightly water soluble (0.4% at 68°F [20°C])
  • Flammability: Highly flammable and explosive between 4% and 45% (concentration in air); may travel to a source of ignition and flash back. Burns to produce a toxic gas, sulfur dioxide.

Possible Health Issues
  • Nausea
  • Headaches
  • Delirium
  • Disturbed equilibrium
  • Tremors
  • Convulsions
  • Skin irratation
  • Eye irratation
  • Unconsciousness
  • Death

PPM Health Chart

Places H2S is found
  • Swamp and sewer environments
  • Volcanoes
  • Hot Springs
  • Underwater sub-sea vents
  • Farming
  • Coal mining
  • Pulp and paper
  • Tanning and smelting industries
  • Petroleum refineries
  • Caves
  • Tunnels
  • Rayon manufacturing
  • Sugar-beet processing
  • Hot-asphalt paving


Agency for Toxic Substances and Disease Registry
United States Department of Labor
National Library of Medicine
The Safety Blog on Safety Tips for the Workplace
Calgary First Aid

Author: Doyle

I was born in Atlanta, moved to Alpharetta at 4, lived there for 53 years and moved to Decatur in 2016. I've worked at such places as Richway, North Fulton Medical Center, Management Science America (Computer Tech/Project Manager) and Stacy's Compounding Pharmacy (Pharmacy Tech).

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