The Deadly Gas You May Be Exposed to at Work: Hydrogen Sulfide
H2S, also known as Hydrogen Sulfide, is the industrial name given to a colorless gas with a powerful and repulsive odor that gives off the smell of rotten eggs or sulfur. It’s used in oil refineries, sewage treatment plants, natural gas processing plants, and other heavy industries where it plays a vital role in converting crude oil into usable products. However, H2S poses serious health risks and can lead to severe injury or even death if the proper safety precautions are not considered.
What is Hydrogen Sulfide (H2S)?
Sometimes called sour gas, hydrogen sulfide is one of many hazardous gases and chemicals used in oil and gas production. When inhaled in large amounts, it can lead to death. This toxic gas has been responsible for numerous fatalities during refinery accidents and oil/gas drilling operations since 1925. Companies operating under a safety culture are focused on prevention—through robust operating procedures, thorough training of employees, and strict adherence to set procedures. One such company is Tesoro Refining & Marketing Company LLC (T&R), which recently spoke with Texas Chemical Council about H2S safety concerns at refineries and operations throughout our state. What follows are portions of that conversation. 1) Why do you think H2S is dangerous? How does it affect workers? Hydrogen sulfide is a unique substance because its toxicity varies greatly depending upon how quickly and how much an individual breathes it. There are no effects or symptoms at low levels, but as exposure increases, so do physiological changes in breathing patterns and increased stress on vital organs. A person’s response will also vary depending upon their activity level, genetics and even what they had for breakfast!
What industries use H2S?
Oil & Gas, Mining, Paper Manufacturing, Pulp Mills, and Forestry are some of those that use H2S regularly. H2S is naturally produced in oil wells during oil production; it causes rotting egg odors that can be easily detected. It may also be present in low concentrations when wastewater from these facilities is discharged into rivers or lakes. When it occurs in high concentrations, it can cause serious health effects and even death. Because your nose cannot detect H2S at concentrations above 500 parts per million (ppm), chemical odorants are often added by industry to make H2S detectable by people through their sense of smell. However, some odorant mixtures have been found to be more toxic than hydrogen sulfide itself. The U.S. Environmental Protection Agency (EPA) regulates H2S as a pollutant under its National Pollutant Discharge Elimination System (NPDES). Industrial sources must obtain an NPDES permit for all discharge of process wastewater containing greater than 10 ppm H2S or 100 ppm total reduced sulfur compounds (TRSC). The EPA has set an exposure limit for occupational exposure at 50 ppm over an eight-hour time-weighted average; however, OSHA sets a permissible exposure limit of 75 ppm over an eight-hour time weighted average and recommends that exposure not exceed 30 minutes per day at any concentration higher than 25 ppm.
Why are we exposed to H2S?
H2S, which smells like rotten eggs, is naturally produced in some oil and gas wells during drilling. The gas can also be found naturally in water wells where bacteria react with decaying organic matter. H2S cannot be seen or smelled by humans until it reaches very high concentrations. When H2S enters our lungs, it forms sulfuric acid – which leads to cell damage that could cause irreversible lung disease or death. Long-term exposure causes chronic inflammation of your airways and lungs. Workers are most often exposed to H2S when it mixes with other gases, such as methane. In these situations, workers may not know they’re being exposed because they can’t smell or see H2S. How do we prevent exposure? There are two ways to prevent breathing in harmful amounts of H2S: mechanical controls and administrative controls. Administrative controls include things like providing information on safe work practices and educating workers on hazards associated with working around certain chemicals. Mechanical controls involve using ventilation systems that capture dangerous gases before they reach people’s breathing zones. By following proper safety protocols outlined in OSHA regulations 29 CFR 1910 Subpart Z, employers can protect their employees from harm caused by hydrogen sulfide exposure.
How do you protect yourself from H2S?
It's called hydrogen sulfide, a colorless gas that can smell like rotten eggs. Breathing in small amounts of H2S won't hurt you—but breathing in large amounts can quickly kill you. If you work around H2S, you must take precautions to protect yourself from exposure; otherwise, your co-workers will be breathing for you. If exposed, follow these emergencies first aid care guidelines until emergency responders arrive on the scene: Seek a fresh air source. Avoid close contact with anyone who is known or suspected to have been exposed and victims who are dead or unconscious. In addition, do not attempt rescue if hazardous materials (HazMat) have also been released during an incident and remain in the environment. Call 911 immediately. Move victim to fresh air. Call 911 or other emergency services provider if available. Apply CPR if trained and equipment is available. Administer oxygen if trained and equipment is available.
How do you test for the presence of H2S?
There are a couple of different ways to test for H2S and each has its benefits depending on how quickly you need your results. The most basic form is through what’s called an odor threshold test. That’s when you walk into a room and get a sense of how solid or potent an odor is. There are also handheld meters that can tell you if there is any H2S in your environment, which will make for faster results than simply detecting an odor, but can still give false positives if not done properly. Finally, there are flame ionization detectors (FIDs) that work by passing flammable gases over a heated coil.
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