Hydrogen Sulfide: Understanding Exposure Risk in the Oil & Gas Sector

Protecting workers against avoidable exposure is the right thing to do.

• By Peter Barratt
• Aug 01, 2022

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, analysing 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. 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. In China, hydrogen sulfide exposure through deep seam coal mining operations has caused 50 fatalities since 2006. 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. 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. 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. 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 to not only source natural gas, but also to gain sulfur resources through extraction. This sulfur recovery process helps offset the cost associated with sour gas field extraction, making it more viable and therefore bringing in more staff to work on it. 

Sour gas is much more corrosive than natural gas, and the pipes carrying it require more regular maintenance and checks to reduce the risks of leaks. The risk of H2S exposure in sour gas processing is high, as the raw gas contains it, and then the refinery process of removing it also creates a risk as it is collected. Equipping workers with PPE, including personal gas detectors, allows them to be aware of the gas concentration levels in the air around them, and act decisively if needed to protect themselves and others. 

Detecting and Preventing Exposure 

Monitoring and recording data have by far been the biggest leap forward in protecting workers who are at risk of hydrogen sulfide exposure. Rather than relying on manual inspection or weekly collated data uploads, gas detection instruments can be worn by workers for advanced detection and monitoring.  

This kind of real-time monitoring means workers can be alerted to any potential exposure to hydrogen sulfide in seconds. Data patterns can be tracked easily by occupational hygienists or site health and safety managers, allowing a potential incident or health risk to be spotted early and resolved before it becomes an issue. Uploading daily data recorded on personal devices also allows for long term exposure tracking of individual health. Occupational hygienists can assess an individual’s likelihood of risk or illness in line with their recorded exposure readings. 

This also helps with a wider health and safety strategy. For example, take a scenario where workers regularly operate in an area of a refinery that exceeds exposure levels within a specific activity. This highlights a need for better training and awareness, and a re-examination of how work is carried out in that area.  

Let’s look at an example of public safety and health. If there are reports in the local community of eye and respiratory irritation (the two most common reactions to low levels of H 2 S), the plant responsible can take action to reduce the levels of hydrogen sulfide in the air concentration through improved air scrubbing and pollution capture technologies.  

In both instances, the data collected from personal devices and the activity of a site helps reaffirm and create robust occupational health and safety strategies that have worker safety at their core. 

Lone workers can be some of the most at-risk staff in oil and mining industries. Inspecting sites that are unmanned, remote or in the process of being decommissioned all pose a high risk to health and safety. Should there be an unknown hydrogen sulfide build up or leak, the lone worker may not be aware until it is too late, and if knockdown happens, they will be unable to call for help. A personal gas detection device would be able to detect the concentration threshold of hydrogen sulfide well before the person got to the stage of being overwhelmed by the gas, thereby alerting the wearer and stopping them from entering a dangerous area. 

With greater monitoring and protection against hydrogen sulfide exposure risks, it is possible to reduce the number of work-related incidents and improve overall worker safety. When it comes to worker health and safety, the benefits of individual gas detection devices are immeasurable at preventing exposure. Protecting staff from potential hazards will only continue to grow in legislative strength as we move into new territories for extracting oil, gas and coal, and as we move into other areas of energy production such as anaerobic digestion and biofuels, both of which carry high risks of hydrogen sulfide exposure.  

By being prepared and equipping staff with appropriate PPE and personal gas detection devices, businesses can create robust occupational health and safety strategies built on pillars of training, awareness, equipment and prevention. As more about the long-term risks of exposure to hydrogen sulfide are uncovered, protecting workers and the public now against avoidable exposure is the right thing to do. Opting for a hydrogen sulfide detection solution is an ideal way for businesses to keep staff safe and protected.  

This article originally appeared in the July/August 2022 issue of Occupational Health & Safety.