Managing Hydrogen Sulfide Exposure Risks

 

Hydrogen sulfide (H₂S) is a flammable, colorless, toxic gas that can occur naturally with liquid hydrocarbon and natural gas exploration, production and processing operations, and presents an exposure risk at Marathon locations where it occurs. The Company minimizes personnel exposure to areas where H₂S exists, and if exposure is unavoidable, provides measures to protect workers from potentially harmful levels of the gas.

OSHA regulations and hazard communication standards, the PSM Standard and API recommended practices are the basis for Marathon's corporate standards to control H₂S exposure.

Marathon limits H₂S exposure through industrial hygiene assessments, mandatory annual employee training, engineering and workplace controls, safe work procedures, signage and other required hazard communications, and PPE such as personal exposure monitors. Engineering controls include vapor recovery units, fixed monitors and flares or remote vents. Fixed and personal monitors sound an alarm when H₂S gas levels are above established limits.

Despite these precautions, one Robinson, Illinois, refinery worker died from H₂S exposure in January 2007, and a natural gas plant employee in New Mexico was overcome by a non-lethal release of H₂S gas in January 2008. To prevent future incidents, Marathon established more rigorous follow-up procedures for alarm events and expanded its requirement for wearing a personal H₂S monitor to all employees, contractor personnel and visitors within Marathon refineries. At the natural gas plant, Marathon installed additional shutdown instrumentation. Management held a stand-down to review the gas plant incident, stressing mandatory compliance with the Company's H₂S exposure control standard.

To strengthen H₂S exposure protection in the transportation supply chain, Marathon personnel led a task force addressing H₂S practices. The result was the first management practice for the control of H₂S in an asphalt facility in North America. The practice will be published by the U.S.-based Asphalt Institute in 2008. Marathon also is participating in an Asphalt Institute task group focused on developing new analytical test methods to identify potential H₂S emissions from black oils. The tests will make it possible to notify the entire black oils supply chain when a shipment may contain elevated H₂S levels.