Industrial fire familiarization: Hydrogen Sulfide

Industrial fire familiarization: Hydrogen Sulfide



Hydrogen Sulfide

Hydrogen Sulfide


HMN-Hydrogen sulfide, or H2S, is a common threat in our industrial environment. Most are taught about the rotten egg smell, and ability to dull the olfactory sense in large doses, but do we really understand it’s presence in our processes?

What exactly is it?

H2S is a colorless, flammable, extremely hazardous gas with a “rotten egg” smell. It is heavier than air and can collect in low-lying and enclosed, poorly ventilated areas such as basements, manholes, sewer lines, and underground telephone/electrical vaults.  (Courtesy of

Where exactly is it?

H2S can be found naturally in raw crude oil or other raw petroleum products along with other sulfur species.  Some crude oils can be low in sulfur percentages, which are known as “sweet” crudes, while some crude oils can contain over 40% sulfur. These crudes high in sulfur are known to be “sour”.  These attributes are not desirable in finished products, and are refined out during the processing, most commonly in “hydro desulfurization” units. In a nutshell, these units use pressure, temperature, a catalyst, and hydrogen to strip these sulfur compounds out, making the product a lower sulfur percentage. However the sulfur bonds with the hydrogen used in the process to make H2S. These streams can have very high purities.


What H2S does.

Symptoms of acute exposure, 10 ppm to 500 ppm, include nausea, headaches, delirium, disturbed equilibrium, tremors, convulsions, and skin and eye irritation. Inhalation of high concentrations of hydrogen sulfide, 500 ppm to 1000 ppm, can produce rapid unconsciousness and death. H2S acts a lot like cyanide exposure in that it has a higher affinity to the red blood cells, there by reducing the amount of O2 on the transport cells. The overall goal in higher exposure is to get O2 back on the cell to oxygenate the vital organs.


Other considerations

While extremely toxic, H2S is flammable, as well as an acid gas. Byproducts of burning H2S can include another toxic chemical known as Sulfur Dioxide. SO2 is a known somatic cell mutagen, and acid gas, which makes for a bad day all around! the While the flammability of h2s limits our PPE selection, our warm and cold zones may be benefited by extra air monitoring or even personal gas detectors. Many manufacturers have personal gas clips for h2s that will alarm in the 10-15 ppm range to alert the user of gas in the area.

Personal gas meter

Personal gas meter

Get to know your facility, and the products involved! Train now to gain the upper hand later.



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