Hydrogen Sulfide Gas Exposure


Hydrogen sulfide (also referred to as sour gas, acid gas, stink damp, rotten egg gas or sulphureted hydrogen) is a highly toxic, colourless gas with the characteristic foul odor of rotten eggs. The gas can be very pungent at first, but quickly deadens the sense of smell which can cause victims to be unaware of its presence until it’s too late. Workers may be adversely affected from H2S exposure ranging from loss of consciousness to death.

Workers with the highest exposure risk may be involved in the maintenance of sewage systems and the oil and gas industry. Enclosed and confined spaces are the danger areas prone to the rapid buildup of hydrogen sulfide gas. These situations also present a serious hazard for rescue and recovery personnel and first responders. The risk of injury after exposure to H2S is compounded by other hazards in the work area. For example, workers that become unconscious after a H2S exposure can easily drown in fluids (water, sewage, process liquids, etc.) or obtain a serious or fatal injury in a fall from heights.


Here are some safety precautions to prevent hydrogen sulfide exposure:

  • Avoid entering or leaning over confined spaces. Confined areas can accumulate gasses like H2S. If the H2S concentration is very high it may overcome the worker even at the sewer entry points or tank opening.
  • Have a competent person complete a hazard assessment. This assessment will determine if a space is safe for a worker to enter. It may also determine if specialized safety equipment is required for the worker to enter the space safely.
  • Monitor air concentrations of H2S using gas monitors. These monitors can be set to alarm and help alert workers to hazards allowing them increased opportunity to escape hazardous environments. The monitors must be calibrated regularly to ensure proper function.
  • Use appropriate personal protective equipment. Some work spaces are only safe to enter with the appropriate personal protective equipment. Ensure that you are provided with PPE and are trained on the proper use.
  • Plan for emergencies. Ensure that emergency procedures and rescue plans have been developed. Workers required to carry out the emergency plan must be trained and readily available.
  • If you are asked to complete a task, ensure that you have been provided with all the essential information. This includes what hazards may be encountered, and what equipment or processes are available to protect you. Training may include H2S Alive, First Aid and Confined Space.