Gases and vapors continue to pose hazards on oil and gas well sites during gauging, fluid transfer, and disposal

August 24, 2018 by Kyla Retzer, MPH; Emily Schmick, MSPH, CIH; Alejandra Ramirez-Cardenas, MPH; Bradley King, PhD, MPH, CIH; and John Snawder, PhD, DABT

Background

1) The worker peers down an open hatch of the oil tank. 2) In some regions, workers gauge oil tanks by opening tank hatches, visually observing liquid levels, and then manually measuring liquid oil levels. 3) As commonly designed, fixed oil tanks often are interconnected for both liquid and vapor, allowing contents to equalize over multiple tanks. Equalization of tanks can result in a high volume of off-gassed vapors when a tank hatch is opened. 4) The windsock is a visual indicator for the worker to stay positioned upwind while gauging. Photo courtesy of OSHA

A previous NIOSH report (2016)1 described the death of nine oil and gas extraction workers that occurred during gauging or sampling activities at open thief hatches on crude oil storage tanks. Hydrocarbon gases and vapors (HGVs) and associated oxygen displacement were the primary or contributory factors in these fatalities. Additionally, wellsite exposure assessments conducted by OSHA and NIOSH identified HGVs at open thief hatches in concentrations that were immediately dangerous to life or health (IDLH) and in excess of the lower explosive limit (LEL), creating a chance for fires and explosions. It has been demonstrated that HGVs can build up under pressure and rapidly escape when thief hatches of production, flowback, and other tanks are opened, creating a highly flammable and oxygen-deficient environment, even in areas not considered to be a confined space. Acute exposure to HGVs can have narcotic effects on workers (i.e. dizziness, disorientation) as well as affect the eyes, lungs, and central nervous system. The simultaneous exposure of HGVs combined with a low oxygen atmosphere may also pose a risk for sudden cardiac death, especially in individuals with pre-existing coronary artery disease. In addition to HGVs, hydrogen sulfide (H2S), a widely recognized hazard in the oil and gas extraction industry, continues to persist as a cause of death among workers2. Hydrogen sulfide is naturally present in some oil and gas deposits and may be produced as a by-product of the desulfurization process of these fuels. Workers in all operations during oil and natural gas exploration and production may be exposed to H2S. This blog provides an update on fatalities, injuries, and exposures associated with hazardous gases and vapors (HGVs and H2S) in the oil and gas extraction industry, and alerts employers to exposures that can occur while working around oil and gas process fluids.