NIOSH and the California Department of Public Health's Occupational Health Branch (CDPH-OHB) have released a safety video that speaks to the hazards workers face when manually measuring the level of oil or fuels in stationary and mobile (fuel trucks) storage tanks.
The video "Protecting Oil and Gas Workers from Hydrocarbon Gases and Vapors" discusses the effects of hydrocarbon gas vapor emissions that contain elements such as methane, ethane, propane, and butane that can be released into a worker's breathing zone when the worker opens the tank.
Vapor emission safety risks are most often found in the oil and gas industries, but any industry that stores hydrocarbon-heavy products must be aware of the dangers of vapor emissions. This includes trucking companies, construction companies that store their own fuel, and maintenance facilities.
Because the pressure inside a tank can vary and the wind/weather conditions surrounding the worker can change quickly, the released gas can either dissipate rapidly or hang in the air around the worker's head when the tank's hatch is opened. The vapor plume can rapidly displace the oxygen and the high concentration of VOCs (volatile organic compounds) can be fatal. Even a brief exposure (30 seconds or less) to high concentrations of hydrocarbons and a low-oxygen atmosphere can result in the rapid onset of respiratory depression, hypoxia, and fatal cardiac. Workers with pre-existing coronary artery disease are at even more risk.
According to the NIOSH hazard alert, acute exposure to hydrocarbon gases and vapors can affect the eyes, lungs, and central nervous system. If present in sufficient concentrations to displace oxygen, exposure can sensitize the heart to stress hormones, causing abnormal rhythms and ventricular fibrillation that can lead to sudden death.
Exposures can also have narcotic effects, causing dizziness, rapid disorientation, and confusion that could lead to loss of judgment, narcosis, and incapacitation.
The American Petroleum Institute issued a new standard, API MPMS Chapter 18.2, Custody Transfer of Crude Oil from Lease Tanks Using Alternative Measurement Methods, last year covering best practice procedures for measuring, sampling, and working around tanks. A read-only version is available on the API.org website.