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NIOSH/OSHA: Nine Oil and Gas Extraction Worker Deaths Tied to Oxygen Deficiency and Hydrocarbon Gas/Vapor Exposure During 2010 to 2015

Release Date: January 28, 2016

In 2013, an occupational medicine physician from the University of California, San Francisco, contacted the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) about two oil and gas extraction worker deaths in the western United States. The suspected cause of these deaths was exposure to hydrocarbon gases and vapors (HGVs) and oxygen (O2)-deficient atmospheres after opening the hatches of hydrocarbon storage tanks. As a result, the physician and experts from NIOSH and OSHA reviewed available fatality reports from January 2010 to March 2015 and identified seven additional deaths with similar characteristics (nine total deaths). The results of the investigation are reported in the January 16, 2016 issue of Morbidity and Mortality Weekly Report.

Workers at oil and gas well sites often manually gauge the level of fluid or collect a sample from storage tanks containing process fluids. These workers climb to the top of the tanks, open a “thief” hatch (a closable aperture on atmospheric tanks, used to sample the tank contents), and either place a device into the hatch to measure the fluid level or lower a “thief” sampler (a hollow tube) into the tank to collect liquid samples.

One of the deaths reported by the California occupational medicine physician occurred in 2012 and involved an oil and gas worker fatality in North Dakota. The North Dakota state medical examiner attributed death to the inhalation of petroleum hydrocarbons. The male worker, aged 21 years, was gauging crude oil production tanks on the well site, at night and alone. A coworker found the victim unconscious near the open hatch. Colleagues initiated cardiopulmonary resuscitation, and the worker was transported to the hospital where he was pronounced dead approximately two hours later. An autopsy found no obvious signs of traumatic injury. Toxicology testing identified detectable quantities of low–molecular weight hydrocarbons (propane and butane), and evidence of heavier molecular weight hydrocarbons. No indication of exposure to hydrogen sulfide (H2S) was identified. Initially, the death was attributed to cardiovascular disease and later to hydrocarbons. The occupational medicine physician subsequently identified a second worker who died from a sudden cardiac event in 2010 while performing tank gauging; H2S was excluded as a factor. As a result of these two fatalities, the physician contacted NIOSH and OSHA.

To identify other oil and gas extraction worker fatalities associated with exposure to HGVs, the physician and experts from NIOSH and OSHA reviewed media reports, OSHA case files, and the NIOSH Fatalities in Oil and Gas database. Cases were defined as non-traumatic oil and gas extraction worker deaths occurring during January 2010 – March 2015, in which the workers 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 H2S, fires or explosions.

All available information on identified fatalities was reviewed, including OSHA investigations, coroner and toxicology reports, gas monitor data, and exposure assessment data.

Key findings of the study included the following:

Oil and gas extraction is a high-risk industry, with overall occupational fatality rates seven times the national average. Although safety hazards in the industry are well-known, few published reports address chemical exposures and acute occupational illness associated with oil and gas extraction. Recent exposure assessments have identified that opening thief hatches and manual gauging or sampling from hydrocarbon-containing tanks, outdoors in nonconfined spaces, are widely practiced and pose substantial and potentially lethal hazards to workers. These hazards include sudden exposure to high concentrations [>100,000 parts per million (ppm)] of low–molecular weight HGVs, accompanied by displacement of air, resulting in O2 deficiency. Inhaled O2 concentrations of <15% can significantly impair central nervous system function, and concentrations of <10% can result in loss of consciousness and possible death within seconds to minutes.

The simultaneous exposure to high levels of low–molecular weight HGVs and a low O2 atmosphere above an open tank hatch poses a risk for sudden cardiac death. Pre-existing coronary artery disease can exacerbate that risk. In addition, high levels of low–molecular weight HGVs can exert anesthetic effects that contribute to central nervous system depression. The exposure-assessment samples also showed concentrations of propane, butane, pentane, and 2-methylbutane exceeding 100% of the lower-explosive limit. Concentrations of explosive gases in excess of 10% of the lower-explosive limit are considered immediately dangerous to life or health.

Health professionals should recognize the signs and symptoms of exposure to high concentrations of HGVs and possible O2-deficient atmospheres in oil and gas workers. Risk control and health and safety professionals need to recognize and act on nonfatal warning signs and symptoms, such as dizziness, confusion, immobility, and collapse for oil and gas workers who might have been exposed to high concentrations of HGVs and to O2-deficient atmospheres.

As required by OSHA regulations, employers should reduce or eliminate the hazard; this can include practices that allow for alternative fluid sample collection points, remote monitoring of fluid levels, proper use of gas monitors, respiratory protection meeting OSHA requirements, and worker training. Employers also need to ensure that workers do not work alone where they might have risks for exposures to high concentrations of hydrocarbons and low-O2 environments. Having automated external defibrillators available at worksites is also important.

The full article, “Sudden Deaths Among Oil and Gas Extraction Workers Resulting from Oxygen Deficiency and Inhalation of Hydrocarbon Gases and Vapors — United States, January 2010–March 2015,” can be accessed at

As a result of the fatalities, exposure assessments, and potential for sudden cardiac death, OSHA, NIOSH, and multiple industry stakeholders collaboratively issued a Tank Hazard Alert on tank gauging at oil and gas well sites at

For additional information, see E&S News Report NR-2015-03-06, NIOSH Reports Suspected Inhalation Fatalities for Oil and Gas Workers over Five-Year Period.

COPYRIGHT ©2016, ISO Services, Inc.

The information contained in this publication was obtained from sources believed to be reliable. ISO Services, Inc., its companies and employees make no guarantee of results and assume no liability in connection with either the information herein contained or the safety suggestions herein made. Moreover, it cannot be assumed that every acceptable safety procedure is contained herein or that abnormal or unusual circumstances may not warrant or require further or additional procedure.

COPYRIGHT ©2016, ISO Services, Inc.