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About Hydrogen Sulfide Gas

 

About H2SHydrogen sulfide (H2S) is a toxic chemical compound commonly encountered as a flammable gas or in a dissolved state.  It is often associated with a "rotten egg" smell, however this only appears at very low concentrations as olfactory fatigue occurs at more dangerous concentrations.

 

MAJOR ISSUES CONCERNING HYDROGEN SULFIDE

Click below to read more about some of the major issues and dangers that the presence of hydrogen sulfide can cause:

 

 

CHEMICAL PROPERTIES

Boiling Point -60.4 °C (-76.7°F)
Melting Point -85.5 °C (-122 °F)
Molecular Weight 34.08
Vapor Pressure 20 atm @ 25.5 °C
Appearance colorless gas
Vapor Density 1.189 (air = 1.0)
Molecular Formula H2S
Odor offensive rotten egg smell (at low concentrations)
Odor Threshold 0.02 ppm (olfactory fatigue at high concentrations)
Solubility soluble in alcohol and water
Autoignition Temperature 260 °C (500 °F)

 

HAZARDS

H2S gas is toxic, flammable and an environmental hazard.  It is heavier than air, which means it can pool in enclosed environments such as sewer shafts.  Those working in and around sewer and waste disposal systems, in the oil and gas industry, and in certain paper mills and chemical plants are susceptible to exposure.  You can read more about the health and safety dangers of H2S here.

OSHA has prepared the following fact sheet on hydrogen sulfide hazards in the workplace.

H2S FACT SHEET

(pdf)

 

TOXICOLOGY

The EPA has prepared the following report on the toxicology of exposure to hydrogen sulfide.

TOXICOLOGY REPORT

(pdf)

Observed symptoms can depend on the degree of concentration and the length of exposure, including:


1000 – 2000 ppm: Breathing stops due to paralysis of the respiratory system.

500 – 1000 ppm: Breathing rates speed up followed by suspension of breathing at higher concentrations.  Prolonged exposures can cause pulmonary edema (swelling and accumulation of fluid in the lungs).

50 – 500 ppm: Respiratory tract and eye irritation. Prolonged exposures to concentrations between 50 and 600 ppm can cause pulmonary edema (swelling and accumulation of fluid in the lungs). Olfactory fatigue occurs at concentrations between 150 and 200 ppm.

5 - 50 ppm: Irritation of the eyes.

Long term effects from repeated hydrogen sulfide exposure are uncertain, but symptoms may include dizziness, headaches and fatigue. H2S is not regarded as a cumulative toxin.


 

Sources:

Hydrogen Sulfide. Documentation of the Threshold Limit Values and Biological Exposure Indices, 7th ed.; American Conference of Governmental Industrial Hygienists, Inc.: Cincinnati, OH, 2001; Vol. 2.

Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed.; Kroschwitz, J. I., Ex. Ed.; John Wiley: New York, 1991; Vol. 23, p 282.

Hydrogen Sulfide. Documentation of the Threshold Limit Values and Biological Exposure Indices, 7th ed.; American Conference of Governmental Industrial Hygienists, Inc.: Cincinnati, OH, 2001; Vol. 2.

http://www.osha.gov/dts/sltc/methods/validated/1008/1008.html

 

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