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Hydrogen Sulfide

Hydrogen Sulfide 

Mechanism of action:

  • Just like cyanide, it inhibits cytochrome 4 of the electron transport chain. It also bind the heme moiety like CO. 
  • Once inhaled, hydrogen sulfide ionize and are metabolized to sulfides and sulfates, interfering with cytochromes and metalloproteins. 

How to make:

  • As per a Japanese case report: 610HAP[20-25% calcium polysuflides] (a 440 g bottle of a liquid bath essence containing 160-195 g/kg sulfur) and 10 of Sunpole (a 500 mL bottle of a toilet bowl cleaner containing 9.5% HCl)
  • In the US: HCl + “Lime Sulfur Spray”
  • The reaction between calcium sulfate salts and  results in volatilized yellow/green residue on windows maybe visible, smells of rotten eggs

Dose response:

  • 20-100ppm=mild mucous membrane irriation
  • 100-150ppm=olfactory nerve paralysis
  • 150-300ppm=respiratory mucosal irratation and possibly ARDS
  • >500ppm=rapid loss of consciousness
  • >700ppm=cardiopulmonary arrest
  • >1000ppm=cessation of breathing after 1-2 breaths

Intentional uses:

  • Chemical weapon: The main documented deployment of H2S during warfare was by the British during World War 1.
  • “Chemical” suicide: There have been numerous documented cases of completed suicides in vehicles. Often times the victims will place up warning signs so rescue workers are notified of the toxic gas so they can take protective measures.


Occupational exposures:

  • Sewer workers in confined spaces. It is produced by bacterial metabolism and is more dense than air so it sinks to the low points of enclosed systems. The classic presentation is that 1 worker enters a low spot and collapses and has immediate respiratory arrest. Once the first worker does not return, another one follows them and suffers the same fate. The term for this is a “knock-down”.
  • Seismic activity: volcanoes, hot springs, etc.
  • Oil and gas workers.

Clinical findings:

  • Acidosis not explained by other cause
  • Pulmonary edema
  • The symptoms will be similar to any mitochondrial toxin, eg cyanide. So expect, shock, circulatory collapse, and altered mental status.
  • including delayed neuropsychiatric effects


  • A history of an exposure will be the strongest indicator in combination with the clinical data.
  • Diagnostic testing for H2S includes measurement of blood and urine thiosulfate, but will likely take days to weeks to result because it requires a specialized medical laboratory.
  • Basic labs, including a blood gas and a lactate concentration.


  • Remove  victims from contaminated area
  • Aggressive supportive care
  • 100% NRB vs ?HBO
  • Sodium nitrate (theoretical like cyanide, and may reverse sulfmethemoglobinemia); avoid sodium thiosulfate.

Image references: 

all images public domain license

image 1: https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Hydrogen-sulfide-2D-dimensions.svg/2880px-Hydrogen-sulfide-2D-dimensions.svg.png

Image 2: http://hendonpub.com/assets/articles/5110/206a8b6b-1c8f-4546-a48f-17d83b1972fd.jpg


PMID: 18516944


Goldfrank’s Toxicologic Emergcies, 11e

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