Background 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
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