Hydrogen sulfide is a colorless, flammable gas with the chemical formula H₂S, consisting of two hydrogen atoms bonded to a sulfur atom in a bent molecular shape. Known for its characteristic “rotten egg” smell, this toxic compound was first documented by Carl Wilhelm Scheele in 1777 and occurs naturally from decomposing organic matter, volcanic activity, and bacterial processes. While notorious as a deadly gas that has claimed many lives in sewers and industrial accidents – paralyzing the sense of smell before delivering a fatal dose – hydrogen sulfide plays surprising roles in human biology as a gasotransmitter similar to nitric oxide, regulating blood pressure and protecting organs from damage. Produced in vast quantities by the petroleum industry where it must be removed from “sour” crude oil and natural gas, H₂S is both a hazardous waste product requiring careful handling and a valuable source of elemental sulfur for fertilizers and chemicals.

Find a review of the 50 most important industrial gases here.

20 Fun Facts About Hydrogen Sulfide

Beyond the basics above, what else should we know about Hydrogen Sulfide? Check out the 20 fun facts below!

1. H₂S deadens your smell receptors at 100 ppm, meaning you stop smelling it just as concentrations become immediately dangerous.
2. Your body produces about 1 liter of hydrogen sulfide gas daily in the colon, contributing to flatulence odor.
3. The Black Sea contains enough dissolved H₂S below 200 meters to kill all oxygen-breathing life, creating the world’s largest dead zone.
4. Hydrogen sulfide allows some animals to enter suspended animation – mice survive 6 hours in 80 ppm H₂S with no heartbeat.
5. The gas is heavier than air (1.19 times) and has caused mass deaths in valleys where it accumulated from volcanic activity.
6. Sewer workers carry electronic H₂S monitors alarming at 10 ppm because “rotten egg” smell vanishes at lethal levels.
7. The compound tarnishes silver instantly, which is why silverware blackens near eggs and rubber bands destroy jewelry.
8. Hot springs at Yellowstone emit 20 tons of H₂S daily, supporting unique bacteria that use it instead of sunlight for energy.
9. Hydrogen sulfide ice forms at -86°C with a structure completely different from water ice despite similar molecular shapes.
10. The petroleum industry removes 70 million tons of H₂S annually from fossil fuels using the Claus process to make sulfur.
11. Scientists discovered H₂S acts as a neurotransmitter in 1996, regulating memory formation in the hippocampus.
12. The gas liquefies at -60°C and can be transported in railcars, though a single leak could create a deadly vapor cloud.
13. Venus’s atmosphere contains H₂S that reacts with SO₂ to possibly create metallic frost on mountain peaks.
14. Beano and similar products work by breaking down oligosaccharides before gut bacteria can convert them to H₂S.
15. The molecule’s 92.1° bond angle makes it polar enough to dissolve in water but not enough to hydrogen bond strongly.
16. Mass extinctions 250 million years ago may have been caused by ocean bacteria producing massive amounts of H₂S.
17. Paper mills were notorious H₂S polluters until the 1970s, with odors detectable 40 miles downwind at 0.002 ppm.
18. The compound glows blue when burned, producing SO₂ and water with a flame temperature of 1,350°C.
19. Hydrogen sulfide therapy shows promise for heart attack treatment by inducing protective hypothermia at the cellular level.
20. Natural gas is considered “sour” above 5.7 mg/m³ H₂S content, requiring expensive sweetening before pipeline transport.

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