The Complete Beginner's Guide To Hydrogen Sulfide – Compliance Solutions

The Complete Beginner's Guide To Hydrogen Sulfide

The Complete Beginner's Guide To Hydrogen Sulfide

What is H2S?

H2S is the abbreviation for hydrogen Sulfide, hydrogen sulfide is a colorless gas that is known for its rotten egg smell. H2S is extremely flammable and toxic to people! H2S gas can make a person lose their sense of smell very quickly which makes it even more dangerous! This gas is heavier than air and can accumulate in low level, poorly ventilated and enclosed areas.

Some common places where H2S accumulates: 

  • Basements
  • Manholes
  • Sewer Lines
  • Manure Pits

These major industries have a higher risk of exposure to hydrogen sulfide:

  • Oil and Gas Processing & Refining
  • Oil and Gas Exploration
  • Mining
  • Tanning
  • Rayon manufacturing
  • Pulp and Paper Processing
  • Agriculture
  • General Industry
  • Manufacturing

How is Hydrogen Sulfide Gas Created?

Hydrogen Sulfide is produced from the bacterial breakdown of organic materials, human waste, and animal waste. Other activities that can produce H2S include; wastewater treatment, liquid compressed gas, paper mills, and drilling or refining of natural gas or petroleum.

H2S Exposure Health and Safety Effects:

Hydrogen Sulfide effects can range from eye, nose, and throat irritation to death look below for more information on the concentrations and symptoms/effects. (All concentrations will be in PPM or parts per million)

0.00011 to 0.00033 PPM
This is the typical background concentrations of Hydrogen sulfide.

0.01 to 1.5 PPM
This is where some people will start to smell the rotten egg smell hydrogen sulfide is known for.

2 to 5 PPM
Exposure may cause nausea, headaches, and eyes tearing. It may also cause bronchial constriction in some asthma patients.

20 PPM
20 PPM will cause fatigue, headache, loss of appetite, poor memory, irritability, and dizziness.

50 to 100 PPM
Exposure will cause conjunctivitis and respiratory tract irritation after an hour. It will also cause a loss of appetite and an upset stomach.

100 PPM
Exposure at 100 PPM will cause cough, loss of smell, and eye irritation between 2 and 15 minutes. Between 15 and 30 minutes of exposure will cause altered breathing and drowsiness. After an hour of exposure, you will have throat irritation and the severity of symptoms will increase over time and can cause death after around 48 hours.

100 to 150 PPM
100 to 150 PPM will cause a complete loss of smell.

200 to 300 PPM
Exposure will cause marked conjunctivitis and respiratory tract irritation after an hour. Pulmonary edema may occur with prolonged exposure.

500 to 700 PPM
Exposure will cause staggering and collapsing after only 5 minutes. You will have serious damage to the eyes after 30 minutes and death between 30 and 60 minutes.

700 to 1000 PPM
Exposure will cause immediate collapse and unconsciousness after 1 to 2 breaths you will then stop breathing altogether and will die within minutes.

1000 to 2000 PPM
Exposure will cause instant death.

Long time health effects of exposure to Hydrogen Sulfide:

People that have experienced levels of hydrogen sulfide to make them pass out have experienced headaches, poor attention span, memory problems, and problems with motor function after waking up later on after being exposed. Exposure to hydrogen sulfide levels above the PEL (permissible exposure limits) has been known to cause cardiovascular system problems later in life.

What is OSHA’s Permissible Exposure Limit (PEL) for Hydrogen Sulfide?

First off what does permissible exposure limit mean? The permissible exposure limit or PEL is the maximum amount or concentration of a chemical like hydrogen sulfide that a person can be exposed to.

The following are hydrogen sulfide permissible exposure limits for common industries (all in PPM parts per million):

  • General Industry Ceiling Limit: 20 PPM
  • General Industry Peak limit: 50 PPM for up to 10 minutes if no other exposure occurs during shift
  • Construction 8 Hour Limit: 10 PPM
  • Shipyard 8 Hour Limit: 10 PPM

    There are also the limits that NIOSH suggests:

    • NIOSH REL (recommended exposure limit): 10 PPM (10 minutes ceiling)
    • NIOSH IDLH (Immediately dangerous to life and health): 100 PPM
    What is IDLH? IDLH stands for immediately dangerous to life and health, in this case, it would also include the level that interferes with the ability to escape.

    H2S Hazard Levels (API Condition)

    There are four levels of H2S hazards of API Conditions including No Hazard Condition, API Condition 1 Low Hazard, API Condition 2 Medium Hazard, and API Condition 3 High Hazard.

    No Hazard Condition
    No Hazard Condition is a work area where there is no hydrogen sulfide gas present and no hydrogen sulfide protection equipment will be required.

    API Condition 1 Low Hazard
    API Condition 1 or Low Hazard is a work area where the concentration of H2S gas is less than 10 ppm (parts per million).

    Recommendations for these work sites include:

    • Hydrogen sulfide warning sign a green flag warning
    • Keep all H2S equipment in working order
    • Store the H2S protective equipment in an accessible location

    API Condition 2 Medium Hazard
    API Condition 2 or Medium Hazard is a work area where concentrations of H2S gas are greater than 10 ppm and less than 30 ppm (parts per million).

    Recommendations for this work site include:

    • Hydrogen sulfide warning sign yellow flag warning
    • Pay close attention to visual and audible alarm systems
    • Keep all H2S safety equipment in working order
    • Keep a safe distance from dangerous locations (unless you are working to decrease them)
    • Store equipment in an accessible location

    API Condition 3 High Hazard
    API Condition 3 or High Hazard is a work area where concentrations of H2S gas are greater than 30 ppm (parts per million).

    Recommendations for this work area:

    • Hydrogen Sulfide warning sign red flag warning
    • Pay attention to audible and visual alarms
    • Make at least two exits at each location
    • No employees without Hydrogen Sulfide Training
    • Store equipment where it is accessible
    • Place signs 500 feet from the location on every road leading to the site that warns of hydrogen sulfide hazards
    • Make sure all equipment is ready for use before each shift
    • Establish a good means of communication

    Detection of H2S

    Proper training before working around hydrogen sulfide or places that are known to have hydrogen present is incredibly important to get H2S Training today! There are also ways to protect yourself while on the job, each site that could contain H2S should be tested for it before people can enter. If the area is known to contain H2S all workers should wear a have a wearable gas sensor on their body! This will tell workers when the levels of H2S are too high and unsafe to work in. We also suggest you get a detector that has live monitoring so someone outside of the area can keep track of you and the hydrogen sulfide levels in case something happens they can get you out.


    In this blog, we go over a ton of information about Hydrogen sulfide! First, we started by going over what is H2S including places H2S accumulates, major industries with a high chance of exposure, and how H2S is created. Next, we went over the effects on health and safety that hydrogen sulfide causes including all the concentration levels effects and symptoms, long term health effects of hydrogen sulfide exposure, OSHA Permissible exposure limits for hydrogen sulfide, and the H2S Hazard Levels (API Condition). Last we went over what is used to detect H2S Gas and keep employees safe!

    Do you work around hydrogen sulfide? Get H2S Certification today!

    H2S Training (Agriculture Industry)
    H2S Training (General Industry)
    H2S Training (Oil and Gas Industries)

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