Sudden Deaths Due to Oxygen Deficiency and Inhalation of Hydrocarbon Gases and Vapors Among Oil and Gas Extraction Workers — United States, 2010–March 2015

BACKGROUND:  On oil and gas well sites, workers often manually gauge the level of fluid or collect a sample from storage tanks containing process fluids. Recent exposure assessments have identified that opening hatches and manually gauging or sampling from hydrocarbon-containing tanks outdoors in non-confined spaces can result in sudden exposure to high levels of low molecular weight hydrocarbon gases and vapors (HGVs) (>100,000 ppm), accompanied by displacement of air, resulting in oxygen deficiency. These conditions can result in loss of consciousness and possible death within seconds to minutes.

METHODS:  In 2013, an occupational medicine physician from the University of California, San Francisco, received two reports of oil and gas worker fatalities in North Dakota and Montana where both workers were gauging crude oil production tanks alone on the well site at night. The physician, NIOSH, and OSHA subsequently reviewed media reports, OSHA case files, and the NIOSH Fatalities in Oil and Gas database for all workers who were 1) performing tank gauging, sampling, or fluid transfer activities at oil and gas well sites; 2) working in proximity to a known and concentrated source of HGVs (e.g., an open hatch); 3) not working in a confined space; and 4) not exposed to hydrogen sulfide (H₂S), fires, or explosions.

RESULTS:  Nine deaths were identified between January 2010 and March 2015. All of the victims were working alone at the time of the incidents and were found collapsed on the tank(s), catwalk, or at the base of the catwalk stairs. The medical examiner noted petroleum hydrocarbon vapors as a cause of death for three workers. At the time of death of one worker, the personal data-logging continuous multi-gas monitor showed oxygen deficient conditions as low as approximately 7%, with flammable HGV concentration in excess of the lower-explosive limit.

CONCLUSIONS: Health and safety professionals should recognize that oil and gas extraction poses a risk of life-threatening exposure to high concentrations of HGVs and oxygen deficiency. Medical examiners and coroners investigating worksite fatalities should be aware that HGV exposures might result in sudden cardiac death and should obtain appropriate post-mortem toxicology analyses. Employers should implement measures to significantly reduce or eliminate HGV exposures by 1) using remote tank gauging procedures, 2) training workers on identified hazards associated with gauging and sampling, 3) establishing emergency procedures, and 4) assessing and managing hazards by using appropriate gas monitors and implementing respiratory protection programs as required by OSHA.