Occupational Health Hazards of Hydrogen Sulfide

What Is Hydrogen Sulfide?

Hydrogen Sulfide or H2S is a very toxic gas. It has no colour, but it smells like rotten eggs. In large amounts H2S blocks the sense of smell.  

Hydrogen sulphide is a by-product in many different industries, such as: sewers and sewage treatment plants where organic matter break down without oxygen. The petroleum industry, especially at oil and gas well, in refineries where H2S is removed from natural oil and gas; and in pipelines used to carry unrefined petroleum. In some mines and tunnels where mineral rock may contain H2S. The pulp and paper industry where H2S is a by-product of wood breaking down into pulp.

Why Is Hydrogen Sulfide Harmful?

Hydrogen sulfide is a highly flammable, explosive gas, and can cause possible life-threatening situations if not properly handled. In addition, hydrogen sulfide gas burns and produces other toxic vapors and gases, such as sulfur dioxide. 

As the concentration of hydrogen sulfide increases the hazard level increases as well. In high concentrations a knockdown (rapid unconsciousness) effect can occur in 1 or 2 breathes and can result in falls that can seriously injure the worker. 

H2S has a toxicity similar to carbon monoxide, which prevents cellular respiration. Monitoring for H2S in your workplace and early detection could mean the difference between life and death. 

H2S is considered a confined space hazard. It is heavier than air. It settles in low spots. This can pose risks when entering areas like confined spaces where the gas may be present. Concentrations can reach levels that are lethal in a very short amount of time.  

How Does Hydrogen Sulfide Harm My Body?

At lower levels of the gas, the following symptoms can occur a few minutes after exposure  to hydrogen sulphide, or be delayed for several hours. 

Hydrogen Sulfide Poisoning Symptoms

  • H2S is an irritant. Eye irritation can include soreness, light sensitivity, seeing rainbows or a gritty pain with a spasm of the eyelid known as gas eye. 
  • Breathing irritation can include sore nose and throat, a burning feeling in chest and fluid build-up in the lungs. 
  • Other symptoms include headache, confusion, nausea, disorientation, or vomiting. 

With high concentrations of H2S, poisoning can be quick and deadly – with little warning. If a worker is not protected adequately the effects can occur within a few breaths, and possibly a single breath if concentrations are high enough. Rapid unconsciousness also called a "knockdown" or immediate collapse can occur within 1 to 2 breaths. 

The body can shake, and death follows in seconds or minutes as a result of breathing failure.

Who Needs To Be Concerned About Hydrogen Sulfide Hazards in the Workplace? 

Let’s review some industries and their activities that product Hydrogen Sulfide. 

Sewage Systems

  •  Anywhere organic material is left to break down

Oil & Gas

  • Natural gas well sites, at petroleum refineries and in pipelines used to carry crude oil and natural gas, where H2S is naturally occurring. Many oil and gas activities have the potential to release H2S. This can include drilling and completions operations, flowback testing, plant operations, and well treatment and transportation of production fluids. H2S can also be produced as a by-product during the treatment of wells with mineral acids.


  • In tunnels where mineral rock contains hydrogen sulfide. 

Pulp & Paper

  • By-product of wood breaking down into pulp. 


  • Compost and manure piles 


  • Excavations in landfills and swamps

How to Mitigate H2S Hazards in the Workplace 

If you work in any of the industries listed above, it important to ensure there is a hydrogen sulfide exposure control plan in place when disaster strikes. Contact Chemscape Safety Technologies today to learn how we can help elevate the level of occupational health standards for your company.


Elevate the level of occupational health hazards for your company.