Health and safety risks for workers involved in manual tank gauging and sampling at oil and gas extraction sites
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Health and safety risks for workers involved in manual tank gauging and sampling at oil and gas extraction sites

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    The National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) have identified health and safety risks to workers who manually gauge or sample fluids on production and flowback tanks from exposure to hydrocarbon gases and vapors, exposure to oxygen-deficient atmospheres, and the potential for fires and explosions. This Hazard Alert describes the safety and health hazards when workers manually gauge or sample fluids from production, flowback, or other tanks. It recommends ways to protect workers by eliminating or reducing exposures to hazardous atmospheres, and actions employers should take to ensure that workers are properly aware of the hazards and protected from exposure to hydrocarbon gases and vapors. This alert is a supplement to the OSHA Alliance Tank Hazard Alert released in 2015 [National STEPS Network 2015]. NIOSH and OSHA also identified nine worker fatalities that occurred while workers manually gauged or sampled production tanks from 2010-2014 [NIOSH 2015]. Exposures to hydrocarbon gases and vapors and/or oxygen-deficient atmospheres are believed to be primary or contributory factors to the workers' deaths [Harrison et al. 2016]. NIOSH & OSHA Recommendations for Manual Tank Gauging and Fluid Sample Collection: 1. Implement alternative tank gauging and sampling procedures that enable workers to monitor tank fluid levels and take samples without opening the tank hatch. 2. Retrofit existing tanks with dedicated sampling ports (i.e., tank sampling taps [American Petroleum Institute 2013]) that minimize worker exposures to hydrocarbon gases and vapors, thereby eliminating the need to routinely open thief hatches to sample. These sampling taps should minimize the magnitude of hydrocarbon plumes and should limit the need for workers to access the top of tanks. 3. Install thief hatch pressure indicators to provide an immediate visual indicator of tank pressures and potential hazards. Pressure indicators can show workers the pressure in the tank and allow a trained worker to follow appropriate procedures, such as actuating a blowdown valve, venting gas to a flare, or using appropriate respiratory protection, such as a self-contained breathing apparatus or an air-line respirator. 4. Conduct worker exposure assessments to determine exposure risks to volatile hydrocarbons and other contaminants. Employers may consult an occupational safety and health professional trained and certified in industrial hygiene and who has knowledge and experience with combined flammable gas and vapor exposures to ensure that an appropriate air-sampling strategy is used. 5. Provide hazard communication training in a language that employees understand to ensure that general site workers, tank gaugers and samplers, water haulers, drivers, and others who open tank hatches understand the hazards associated with opening tanks and the precautions necessary to conduct this work safely. These hazards include reduced oxygen environments, flammability hazards and possible ignition sources, and the potential for concentrations of hydrocarbons that can approach or exceed IDLH concentrations. Post hazard signage at access stairs, catwalks, and/or tanks to alert workers about the hazards associated with opening thief hatches and precautions that must be taken. 6. Ensure that workers are trained on - and correctly and consistently use - calibrated multi-gas and oxygen monitors that measure percent LEL and oxygen concentration. Workers should understand the limitations of these monitors as well as appropriate actions to take whenever an alarm occurs or they experience health symptoms (e.g., leave the hazard area, report symptoms to supervisors). 7. Do not permit employees to work alone when tank gauging or working around tanks, thief hatches, or other areas where they may encounter process fluids. Observers should be trained on proper rescue procedures and be stationed outside potentially hazardous areas. 8. As an interim measure, where remote gauging or sampling is not feasible or engineering controls are not implemented, (a) train workers in proper work practices, such as tank-opening procedures, that can minimize risks for exposures, (b) ensure intrinsic safety by proper grounding and prohibiting the use of spark producing devices or equipment, (c) establish administrative controls to reduce the number of times throughout a shift a worker is required to manually gauge tanks, (d) safely reduce tank pressure prior to gauging, and (e) use appropriate respiratory protection, including a supplied air respirator (SAR) and/or self-contained breathing apparatus (SCBA) in areas where IDLH VOC exposures may occur (i.e., during manual tank gauging/sampling). Employers should consult with a trained occupational safety and health professional to determine the appropriate respirator to be used. NIOSH guidance for selecting respirators is at: 9. Wear flame-resistant clothing to protect against burns from fires and explosions. Also, use appropriate impermeable gloves to limit risks for skin exposures to chemicals (e.g., benzene). 10. Establish and practice emergency procedures to provide on-scene, immediate medical response in the event of an incident, such as a collapsed worker, or workers experiencing symptoms of chemical overexposures or exposure to an oxygen-deficient atmosphere.

    NIOSHTIC no. 20047454

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