Hydrogen Sulfide in Workplaces
Hydrogen sulfide is produced naturally from decaying organic matter. It can be released from sewage sludge, liquid manure, and sulfur hot springs, and with natural gas. It is also used or is a by-product in many industrial processes such as:
- Petroleum production and refining
- Sewer and wastewater treatment
- Agricultural silos and pits
- Textile manufacturing
- Pulp and paper processing
- Food processing
- Hot asphalt paving
Many workers are at risk for exposure to hydrogen sulfide, especially when working in confined spaces. For example,
- Sanitation workers can be exposed when cleaning or maintaining municipal sewers and septic tanks.
- Farm workers can be exposed when cleaning manure storage tanks or working in manure pits.
- Workers in oil and natural gas drilling and refining may be exposed because hydrogen sulfide may be present in oil and gas deposits and is a by-product of the desulfurization process of these fuels. See OSHA Oil and Gas Well Drilling and Servicing eTool.
In general, working in the following areas and conditions increases a worker’s risk of overexposure to hydrogen sulfide:
- Confined spaces (for example pits, manholes, tunnels, wells) where hydrogen sulfide can build up to dangerous levels.
- Windless or low-lying areas that increase the potential for pockets of hydrogen sulfide to form.
- Marshy landscapes where bacteria break down organic matter to form hydrogen sulfide.
- Hot weather that speeds up rotting of manure and other organic materials, and increases the hydrogen sulfide vapor pressure.
OSHA Safety and Health Information Bulletins (SHIBs)
- Chemical Exposures from Industrial Valve and Piping Systems. (May 14, 1996). Discusses the potential hazard that exists for releasing hazardous chemicals into the workplace when a normally closed system is opened.
- Corrosion of Piping in Hydroprocessing Units. (July 29, 1994). An explosion and fire resulted when severe corrosion caused the failure of the hydrocracking Reactor Effluent Air Coolers (REAC) and adjacent piping at a refinery.
- Anaerobic Decomposition in Cooling Water Systems. (March 5, 1990). A fireball developed when a pipefitter used a cutting torch on a cooling water system pipe. Hydrogen sulfide created from anaerobic decomposition was the probable causative agent for the production of explosive gases.
- U.S. Labor Department's OSHA cites excavation and utilities company following fatality at Gordon, Texas, facility. (December 21, 2011).
- U.S. Department of Labor's OSHA cites 5 companies for exposing workers to hydrogen sulfide at Eustace, Texas, work site. (April 8, 2011).
- U.S. Department of Labor's OSHA cites Matula & Matula Construction following worker death in Lake Jackson, Texas. (August 5, 2010).
- U.S. Labor Department's OSHA cites Enbridge G&P in Douglasville, Texas, following worker fatality from release of hydrogen sulfide. (July 8, 2010).
- U.S. Labor Department's OSHA cites Chipco LLC in Zanesville, Ohio, following fatality at natural gas well site in Londonderry, Ohio. (March 8, 2010).
- U.S. Labor Department's OSHA cites two employers following confined-space deaths at Queens, NY, recycling facility. (January 12, 2010).
- U.S. Department of Labor's OSHA proposes more than $1.4 million in penalties in connection with fatal explosion in Houston. (January 4, 2010).
- U.S. Department of Labor's OSHA cites chemical recycling company following a fatality at Port Arthur, Texas, worksite. (October 9, 2009).
- U.S. Department of Labor's OSHA cites Suncor Energy (U.S.A.) Inc. in Commerce City, Colo., for workplace safety and health violations. (March 6, 2009).
A 49-year old sanitation worker died when rescuing a co-worker from an underground sewer vault when he was overcome with hydrogen sulfide gas.
Workers who entered a 27-foot deep pit in a marshy area died after being overcome by hydrogen sulfide.
Workers died clearing debris from an underground sewer pipe. Both were overwhelmed by hydrogen sulfide gas. They were 19 and 25 years old.
Two workers died at an oil field water injection plant while replacing a water transfer pump. Hydrogen sulfide was released when a clamp was removed.
A 25-year old waste hauling service worker died after collapsing in an underground manure waste pit. The pit had a square access opening fitted with a removable stainless steel cover. The pit was not equipped with any type of ventilation system or gas monitoring equipment.
Four workers died in an underground lift station that collected leachate from a landfill. One worker entered to replace a sump pump and was overcome by hydrogen sulfide gas. A second, then third, and finally fourth worker entered to attempt rescue. All were overcome and died in the permit-required confined space. A permit entry system had not been established.