Gases and vapors continue to pose hazards on oil and gas well sites during gauging, fluid transfer, and disposalPosted on by
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.
NIOSH has conducted surveillance of worker fatalities and severe injuries in the oil and gas extraction industry, including those that may be associated with exposure to or ignition of hazardous gases and vapors. Fatalities are identified using the NIOSH Fatalities in Oil and Gas Database (FOG). The federal Occupational Safety and Health Administration (OSHA) severe injury data set provides a source to identify severe non-fatal incidents among oil and gas extraction workers. In addition to fatality and injury surveillance, NIOSH has conducted additional worker exposure assessments at oil and gas worksites to examine potential hazardous exposures, including oxygen concentration and hazardous and flammable gas and vapor concentrations (HGVs and H2S) during various worker activities.
NIOSH researchers sought to determine the number of fatalities and hospitalizations with known or potential exposure to hazardous gases and vapors as well as fires and explosions while working around process fluids, including waste water, flowback, petroleum condensate, or crude oil. Waste water is also sometimes referred to as produced water, brine, salt water, etc., but often still contain hydrocarbons.
The following definition was developed to identify cases: During 2015-2016, fatalities or hospitalizations related to the ignition, inhalation, or suspected inhalation of HGVs and/or H2S while handling process fluids (e.g. fluid transfer) or working on tanks containing process fluids at oil and gas well sites or waste water disposal sites. Cases were reviewed and categorized by event type, activity type, location, and fluid type.
During 2015—2016, there were eight oil and gas worker fatalities during eight separate incidents that met the case definition (see cases in FOG Report ).
- Event Type: Three workers died of sudden cardiac death with potential exposures to hazardous gases and vapors, two workers died due to fire/explosions, two workers died due to hydrogen sulfide poisoning, and one worker died due to HGV exposures.
- Activity Type: Four workers died while transferring fluids from tanks to trucks, two workers were tank gauging or sampling, one worker was at an open tank hatch with unknown activity, and one worker was doing hotwork (grinding) on top of a tank.
- Fluid Type: Four workers were working with produced water, three workers were working with crude oil, and one with flowback.
- Site Type: Six workers died at well sites and two workers died at waste water disposal sites.
During 2015-2016, there were ten hospitalizations during ten separate incidents that met the case definition (see cases in FOG Report).
- Event Type: Five workers were hospitalized due to fire/explosions, three workers hospitalized due to H2S exposure, and two workers hospitalized due to HGV exposures.
- Activity Type: Six workers were tank gauging or sampling, one worker was transferring fluids, one worker was using a vacuum truck to remove tank bottoms, one worker was draining condensate from a separator line (i.e. heater treater), and one was transporting waste water.
- Fluid Type: Three workers were working with produced water, one with flowback, one with tank bottoms (solids and waste), one with condensate, one with crude oil, and three were unknown.
- Site Type: Nine workers were injured/exposed at well sites and one worker was injured at a waste water disposal site.
These incidents illustrate that hazardous gas and vapor exposures while handling process fluids continue to occur, either through the inhalation or ignition of hazardous gases and vapors.
In July 2017, NIOSH conducted air monitoring while a trucker was transferring petroleum condensate from a storage tank onto his truck. As hydrocarbon fluids were transferred, gases and vapors that were previously in equilibrium within the storage tank released into the belly of the truck’s tank. To prevent over pressuring of the truck tank as liquid was transferred, the gases and vapors were vented directly to the outside of the back of the truck; no vent line was used to direct the gases and vapors away from the trunk at a distance. Direct reading instrument data and bulk air samples were collected at and around the tanker trunk and later analyzed to determine HGV and H2S concentrations in the air during this activity. Forward-looking Infrared (FLIR) video was used to visualize and record the plume of hazardous gases and vapors that surrounds the tanker truck during the fluid transfer (click for video).
While performing this fluid transfer, hazardous gases and vapors were measured in concentrations over 348,000 parts per million, or 34.8% of the air volume. The full analysis of this air sample is shown in Table 1.
Table 1. Results for select gases and vapors collected during petroleum condensate transfer near the venting point behind the tanker truck
|Gas/Vapor||Concentration (ppm)||IDLH (ppm)||Severity (Concentration/IDLH)|
* Immediately Dangerous to Life or Health (IDLH) values are based on the NIOSH Current Intelligence Bulletin 663, which states “In the event that the derived health-based IDLH value exceeds 10% of the LEL concentration for a flammable gas or vapor, the air concentration that is equal to 10% of the LEL will become the default IDLH value for the chemical.”
** Analysis Method- Gas chromatography-flame ionization detector (GC-FID)
† Analysis Method- Gas chromatography-photoionization detector (GC-PID)
‡ Analysis Method- Direct reading instrument with electrochemical sensor
Recommendations for Employers, Workers, and Incident Investigators
Oil and gas worker fatalities and hospitalizations due to ignition or inhalation of hazardous gases and vapors and associated oxygen deficiency are preventable. There are a number of resources available that employers and workers can use to prevent these incidents.
Implement recommendations contained in the following relevant resources to prevent exposures to hazardous gases and vapors:
- American Petroleum Institute Recommended Practice 77: Risk-based Approach for Managing Hydrocarbon Vapor Exposure during Tank Gauging, Sampling, and Maintenance of Onshore Production Facilities: provides recommended practices for assessing the hazard and selecting proper controls to protect workers.
- American Petroleum Institute Recommended Practice 2219: Safe Operation of Vacuum Trucks Handling Flammable and Combustible Liquids in Petroleum Service: provides guidance on the development and implementation of practical and safe operating practices to identify hazards and reduce risks during vacuum truck operations. Includes information about proper venting of gases and vapors from trucks, including vent lines and other ventilation methods to reduce exposure to workers during fluid transfer.
- American Petroleum Institute. 2016. API MPMS Chapter 18.2. Custody Transfer of Crude Oil from Lease Tanks Using Alternative Measurement Methods: provides recommended practices for crude oil tank gauging and sampling that do not require the opening of tank hatches.
- OSHA/NIOSH Hazard Alert: Health and Safety Risks for Workers Involved in Manual Tank Gauging and Sampling at Oil and Gas Extraction Sites: provides information about worker fatalities during gauging and sampling activities, well-site exposure assessment findings, the potential health effects of HGV exposures, and recommendations for protecting worker safety and health.
- National STEPS Network: Tank-gauging Hazard Alert: a one-page overview of potential safety and health hazards to workers during tank-gauging and fluid sampling (English and Spanish).
- National STEPS Network: Multi-Gas Monitors Hazard Alert: a one-page overview of the importance of the use of multi-gas monitors on oil and gas well sites. Includes the importance of monitor calibration, training of workers, heeding of all alarms, and understanding the limitations of monitors (English and Spanish).
- National STEPS Network: Prevention of Fatalities from Ignition of Vapors: a one-page overview of how to prevent fatalities associated with ignition of vapors by mobile engines and auxiliary motors on oil and gas well sites (English and Spanish).
- National STEPS Network: Hot Work Hazard Alert: a one-page overview of how to prevent fatalities associated with hot work on oilfield tank, tankers and other related equipment (English and Spanish).
- OSHA Safety Bulletin, Potential Flammability Hazard Associated with Bulk Transportation of Oilfield Exploration and Production (E&P) Waste Liquids: bulletin alerting employers and workers about flammable hazards and prevention measures for transporting oil and gas waste water.
- Chemical Safety Board (CSB) Investigation Report: Vapor Cloud Deflagration and Fire: in-depth report of multiple fatality incident resulting from ignition of vapors at a waste water disposal site.
- CSB Safety Video: Death in the Oilfield: tells the story of a fatal explosion due to ignition of vapors during hot work activities on a crude oil tank.
- Video: Protecting Oil and Gas Workers from Hydrocarbon Gases and Vapors: this 13-minute video describes the hazards associated with manual gauging and fluid sampling on oil and gas production tanks and steps that employers and workers can take to do this work safely (English and Spanish).
Comply with all employer policies and hazard assessments to ensure you are protected from hazardous gases and vapors. Always wear required personal protective equipment and your multi-gas monitor and heed all alarms. Review the videos listed above and each of the National STEPS Network Hazard Alerts to learn more ways to protect yourself.
Medical examiners and coroners investigating oil and gas worker fatalities need to be aware of the possibility of hazardous gas and vapor exposures and request appropriate lab tests. Exposure to high concentrations of HGVs and oxygen-deficient atmospheres can result in sudden cardiac death in oil and gas extraction workers. Analysis of ante-mortem or postmortem blood for documentation of HGV exposure (2139B) as well as H2S (thiosulfate in blood) is available from clinical toxicology laboratories.
NIOSH is working with industry partners to continue to evaluate the magnitude of hazards and effectiveness of controls in the oil and gas industry. We are looking for industry partners who are interested in participating in studies and/or providing access to sites to assess exposures. If you have questions, or would like to provide pertinent information on this topic, please contact us via the blog comment box or by email at email@example.com.
Kyla D. Retzer, MPH, is an Epidemiologist in the NIOSH Western States Division.
Emily Schmick, MSPH, CIH, is an ORISE Research Fellow in the NIOSH Western States Division.
Alejandra Ramirez-Cardenas, MPH, is a Research Assistant in the NIOSH Western States Division.
John Snawder, PhD, DABT, is a Research Toxicologist in the NIOSH Division of Applied Research and Toxicology.
Bradley King, PhD, MPH, CIH, is an Industrial Hygienist in the NIOSH Western States Division.
Note: The objective of this blog entry is to describe a potential emerging occupational hazard in the oil and gas extraction industry. Additionally, it is meant to request help from stakeholders for more information related to illnesses, injuries, and fatalities associated with fluid transfer. To keep the blog discussion focused on worker health, we may choose not to respond to comments that do not pertain to worker exposures.
Ted Teske, Ryan Hill, Robert Harrison (California Department of Public Health), Michael Hodgson (OSHA), J.D. Danni (OSHA), Mike Marshall (OSHA), Barbara Alexander
Esswein EJ, Retzer K, King B, Cook-Shimanek M. Environmental and Health Issues in Unconventional Oil and Gas Development. Kaden DA, Rose TL, eds. Waltham MA: Elsevier, 2016 Jan: 93-105.
Harrison RJ, Retzer K, Kosnett MJ, et al. 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. MMWR Morb Mortal Wkly Rep 2016;65:6–9. DOI: http://dx.doi.org/10.15585/mmwr.mm6501a2
NIOSH . Current intelligence bulletin 66: derivation of immediately dangerous to life or health (IDLH) values. Cincinnati, OH: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 2014–100. https://www.cdc.gov/niosh/docs/2014-100/pdfs/2014-100.pdf
- Page last reviewed:May 14, 2019
- Page last updated:May 14, 2019
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