Main Page Content

What is hydrogen sulfide (H 2S)?

Hydrogen sulfide is a colorless gas that smells like rotten eggs. It is flammable at very high concentrations.

Where does hydrogen sulfide come from?

Hydrogen sulfide occurs naturally in some environments (abandoned water wells, gas wells, sulfur springs, swamps, etc.). It is also produced by breakdown of organic matter and can be found in industrial plants, animal farms, sewers or sewage treatment plants.  

How can you be exposed to hydrogen sulfide?

Hydrogen sulfide is present in our environment and you will have had some exposure to it. Hydrogen sulfide usually breaks down in the air and exposure is only likely to occur if there is an ongoing source. It can enter your body when you come into direct contact with it by breathing it in, eating or drinking something contaminated with it, or when it touches your skin. In the body, hydrogen sulfide is broken rapidly to sulfate by liver and is excreted in the urine.

How is hydrogen sulfide detected?

People usually can smell hydrogen sulfide even at very low concentrations in the air, ranging from 0.0005 to 0.3 parts per million (ppm), but smell is a poor warning sign. While initially people can smell H2S, they can become quickly acclimatized to the smell.

What are the health effects of hydrogen sulfide?

Exposure to low concentrations (10-100 ppm) of hydrogen sulfide may cause:

  • irritation to the eyes, nose, or throat
  • difficulty in breathing for some people with asthma 
  • headaches
  • poor memory
  • tiredness
  • balance problems

Brief exposures to high concentrations of hydrogen sulfide (greater than 500 ppm) can cause a loss of consciousness.  In most cases, the person will likely regain consciousness without any other effects.  However, in some people, there may be permanent or long-term effects such as headaches, poor attention span, poor memory, and poor motor function.

What to do if I suspect a hydrogen sulfide gas leak?

If you notice a rotten egg scent and suspect hydrogen sulfide -

  • near your home, call the Spills Action Centre at 416-325-3000 or 1-800-268-6060 (toll-free)
  • inside your home, call your local fire department

Related Content: