Page 18 - OHS, July/August 2022

IH: GAS DETECTION
Hydrogen Sulfifide: Understanding Exposure Risk in the Oil & Gas Sector
Protecting workers against avoidable exposure is the right thing to do.
BY PETER BARRATT
It’s no secret that the upstream and downstream oil and gas sector is necessary for powering the modern world. Oil, gas and coal products are still in high demand, often requiring people to work in difficult conditions that pose a risk to health
and safety for workers, the public and the environment.
However, as technology has advanced, we have improved our recognition of the hazards of operating in proximity to these resources, analyzing and mitigating the impact to worker, public and environmental health through effective monitoring and gas detection technology. Reducing the risks workers face through laws, technology, equipment and training is the best method of creating a safe working environment that understands the risks
involved.
One of the biggest hazards associated with upstream
and downstream oil and gas is the risk of hydrogen sulfide exposure. Hydrogen sulfide (H2S) occurs naturally in crude oil, and increasingly evidence suggests that it is found in deep coal seam mines.1 Sour gas fields are another example of high concentrations of hydrogen sulfide occurring, combined with natural gas deposits. As the challenge of extracting oil, coal and gas for use becomes more difficult, the petrochemical industry is turning to other forms of extraction, such as fracking, deep seam mining and deepwater drilling. Given that hydrogen sulfide is such a risk to workers, care must be taken to protect and prevent exposure, particularly when working with lesser-known methods and in more dangerous settings, such as sour gas fields and the sweetening process.
Between 2001 and 2017, the U.S. Bureau for Labor Statistics reported 106 worker deaths as a result of exposure to hydrogen sulfide.2 In China, hydrogen sulfide exposure through deep seam coal mining operations has caused 50 fatalities since 2006.3
There are, unfortunately, examples of workers on pipelines or manholes being overcome with hydrogen sulfide due to a lack of measurement and monitoring, or a lack of safety equipment, such as ventilators, masks and gas detectors.4 Understanding the potential risk of exposure to hydrogen sulfide is important in highlighting why there is such a need for personal gas detection and PPE to be implemented at all times.
Understanding Exposure Risks of Hydrogen Sulfide
Hydrogen sulfide is considered a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system and respiratory systems are most affected. It is pungent, typically associated with a “rotten egg” smell, but rapidly destroys the sense of smell (anosmia) at high concentrations making it difficult to detect with human senses alone. Hydrogen sulfide is classed as a hazardous gas, making it critical to monitor and manage for health and safety. One of the biggest risks of encountering hydrogen sulfide at high concentrations is the “knockdown” effect, where workers are overcome by the gas concentration and collapse due to exposure—this can lead to death in some cases.
Low level exposure to hydrogen sulfide can cause irritation to the respiratory system, eyes and stomach. Higher concentrations of the gas can lead to unconsciousness, coma and even death.5 Long-term, low-level exposure can impact the cardiovascular and respiratory systems (particularly in the case of asthma). There is also the long-term risk of impact on the brain and neural systems (studies have shown that hydrogen sulfide poisons the brain), potentially resulting in memory issues and decreased function in reaction time, balance and energy.6 The concentration of hydrogen sulfide in the air (parts per million, or ppm) is what determines the exposure risk—and is what makes it so dangerous in confined spaces.
Working with Risks
Maintenance work, such as on gas or crude oil pipelines, repairing or replacing hatches, or within tankers and confined spaces, can pose one of the highest risks for hydrogen sulfide. Workers entering a space may not be expecting to encounter hydrogen sulfide, especially if the work is regular, scheduled maintenance, or does not usually involve hydrogen sulfide risks. Being aware of the possibility for hydrogen sulfide by wearing personal gas detectors, coming equipped with ventilator masks and checking air concentration levels with portable instruments means the risk is reduced and can be actioned appropriately if hydrogen sulfide is present.
As the demand for natural gas increases, exploring options that have previously been unfeasible due to lack of technology or funds are now being considered. Sour gas fields offer the chance
18 Occupational Health & Safety | JULY/AUGUST 2022
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