H2S exposure chart is a very important tool to know the toxicity level of H2S or hyrogen sulfide.

As a very toxic gas, H2S is very deadly since it can kill person in a few seconds if the person is exposed to a high level of H2S gas.

This gas has a specific smell like a rotten egg. Unfortunately, you cannot see the gas, since it is a colorless gas.

H2S or hydrogen sulfide is also known as sewer gas, sour gas, stink damp, and hydrosulfuric acid.

H2S exposure chart serves as a basic reference for workers and employers about the dangerous level of H2S and to prevent H2S poisoning in the workplace.

But before seeing the chart, we will learn a common list of H2S gas sources in the workplace, the safety hazards, and workplace accident statistics that involving H2S.

H2S Sources In The Workplace

You must be able to identify the H2S sources in your workplace in order to control the hazards and prevent its exposure.

When you finish identifying these sources, then the next step that you need to do is to let workers know about their existence.

You can use H2S warning signs or proper safety slogans. Or you can also provide the sources in the hazard mapping in your work area.

So, where can H2S be found in the workplace? Here are the common sources of H2S that generally found in the workplace:

  1. H2S is a by-product of wood breaking down into pulp in the pulp and paper industry
  2. In the construction industry, during excavation work in swamps or old landfills, hydrogen sulfide can be obtained
  3. H2S can also come from sewers, sewage treatment plants, manure tanks, and other areas where organic material breaks down without oxygen
  4. H2S can be found in the refinery industry, especially at oil and gas wells
  5. H2S may be a by-product of an iron smelting plant
  6. In an ethylene generation plant where ethanol is converted into ethylene gas, H2S is a by-product.
  7. Rayon textile production acts as another hydrogen sulfide source in the industry
  8. Food processing is another source of H2S
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What Are The Hazards of H2S?

After knowing the common sources of H2S, then you need to know the hazards of this gas.

As I said before that H2S exposure can be deadly. It depends on the level or concentration of H2S you are exposed to.

Accoring to the Safety Data Sheet (SDS) of H2S, the hazards of H2S are

  • OSHA considers this compound as a hazardous material (29 CFR 1910.1200)
  • It is an extremely flammable gas, category-
  • H2S is a very toxic gas, category-2, where the target organ is the respiratory tract
  • It may form explosive mixtures with air
  • Fatal if inhaled
  • It is very toxic to aquatic life
  • It can cause irritation on the eyes, dizziness, nausea, and death
  • It is also a chemical asphyxiant, which can inhibit the flow of oxygen from our bloodstream to our cells

H2S Work-Related Accident Statistics

In the period of 2011-2017, there were 46 fatalities caused by hydrogen sulfide inhalation, as reported by the US Bureau of Labour Statistics.

It was the second top cause after carbon monoxide inhalation.

source: bls.gov

H2S Exposure Charts

H2S exposure chart is a chart that shows a relation between hydrogen sulfide level or concentration in the air and their effects to human health.

The higher the concentration, the worst the effect will be.

Please refer to the table below for the exposure chart.

Short Term Symptoms/Effects
1000-2000Nearly instant death
700-1000Rapid unconsciousness, “knockdown” or immediate collapse within 1 to 2 breaths,
breathing stops. Death within minutes.
500-700Staggering, collapse in 5 minutes. Serious damage to the eyes in 30 minutes.
Death after 30-60 minutes.
200-300Marked conjunctivitis and respiratory tract irritation after 1 hour. Pulmonary edema
(fluids in lungs) may occur from prolonged exposure.
100IDLH – Immediately Dangerous to Life and Health
Leave area and get to your safety zone
Coughing, eye irritation, loss of sense of smell
Altered breathing, drowsiness after 15-30 minutes
Throat irritation after 1 hour
Gradual increase in severity of symptoms over several hours.
Death may occur after 48 hours
50-100Slight conjunctivitis (eye irritation and redness). Respiratory tract irritation after 1 hour.
May cause digestive upset and loss of appetite.
20Possible fatigue, loss of appetite, headache, irritability, poor memory, dizziness.
2-5Prolonged exposure may cause nausea, tearing of the eyes, headaches or loss of sleep.
Airway problems (bronchial constriction) in some asthma patients.
0.01-1.5Odor threshold (when rotten egg smell is first noticeable to some). Odor becomes more
offensive at 3-5 ppm. Above 30 ppm, odor described as sweet or sickeningly sweet.
Typical background concentrations
Source: nasdonline.org


H2S is a very toxic gas that can cause severe effect to death. So, it is very important to know the H2S exposure charts to understand the relation between their concentration and effects.