What is Hydrogen Sulfide Gas (H2S)? What are the dangers of H2S?

What is Hydrogen Sulfide Gas (H2S)? What are the dangers of H2S?
Garbage and Pollution at the Lakeside - Potential Hydrogen Sulfide Gas Environment

1- What is Hydrogen Sulfide Gas?

Hydrogen sulfide is a colorless, foul-smelling (rotten egg-like), toxic, corrosive and flammable gas with the chemical formula H2S. It is also known as sewer gas or swamp gas.

2- Where Is Hydrogen Sulfide Found? How is it formed?

Hydrogen sulfide can occur naturally in environments such as swamps or sewers through anaerobic respiration by microorganisms. It is also found in varying amounts in gas leaking from volcanoes, raw natural gas and well water. Since hydrogen sulphide is 1.19 times denser than air, it collects near the ground and spreads around. Although hydrogen sulfide is easily recognized by people due to its strong odor, it causes anosmia (loss of smell) in the nose in a short time. This can give people a false sense of security and lead to exposure to lethal doses of hydrogen sulfide.

The sense of smell is not sufficient to detect the presence of hydrogen sulfide. In environments where hydrogen sulfide is potentially present, detection should be carried out using professional gas detectors.

3- What are the Dangers of Hydrogen Sulfide?

Hydrogen sulfide is both toxic and flammable-explosive gas.


Hydrogen sulphide gas is a very toxic gas for humans. If 0.1% hydrogen sulphide is present in the air we breathe, unconsciousness and death can occur in just a few minutes (0.1% vol = 1000 ppm).
Exposure to even small amounts of hydrogen sulfide can cause irritation of the eyes and respiratory system, breathing difficulties, fainting, eye inflammation, redness, pain, tearing, fear of light, dizziness, headache, weakness, irritability, insomnia, and digestive system disorders. According to the limits specified by the US National Institute of Occupational Health and Safety (NIOSH), if there is up to 10 ppm of hydrogen sulfide in the working environment, people should not stay for more than 10 minutes, and if there is 100 ppm of hydrogen sulfide, the environment should be left immediately.


Hydrogen sulphide is not only dangerous because it is toxic, it is also a flammable-explosive gas. Hydrogen sulphide gas, which has a lower explosion limit (LEL) of 4% and an upper explosion limit (UEL) of 44%, can accumulate especially in closed environments and cause explosions by igniting with a source such as a welding machine, lighter, spark, and can cause loss of life and property.

4- How to detect hydrogen sulfide gas?

For the safe detection of hydrogen sulfide gas, professional gas detectors with electrochemical sensor technology must be used. The Karf&Scoot GD2G Hydrogen Sulfide Detector detects hydrogen sulfide gas precisely, quickly and reliably. Thanks to its analog and digital signal outputs, it can be used alone or combined with the equipment in your facility. Suitable for use in explosive atmospheres, Atex certified. Its robust body made of aluminum and stainless steel provides flawless measurement even in harsh industrial conditions. (For other gases and measurement ranges, please see our GD2G Electrochemical Detector page).

Hazardous gas detection technologies are essential equipment for your personnel and facility safety. For more detailed information and customized gas detection solutions for your facility, you can contact us from our contact e-mail below or from our contact page.

Author: Karf&Scoot
Copying or citation without permission is prohibited.

1- US National Institute of Occupational Health and Safety (NIOSH)
2- International Labor Organization (ILO)

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