During water sector projects, it's important to assess the presence of H₂S and implement routine measurements.
2nd February 2026
Hydrogen Sulphide (H₂S) is a chemical that is often found in water sources and, as a result, in water treatment facilities. It is a colourless gas which is well-known for a distinctive smell that is similar to rotten eggs.
When working on a project in the water sector, it’s vital to identify whether H₂S is present and, where possible, take regular measurements. This is because the presence of H₂S in water systems can cause a number of problems for the project team, environmental health and the broader community if not carefully managed.
How Does H₂S Enter the Water?
These factors contribute to the presence of the Hydrogen Sulphide compound in water which can lead to unpleasant odours and impact the taste and quality of drinking water later in the process. It is important to address the presence of H₂S to ensure that water infrastructure in place, remains safe during the existing water treatment process.
Risks and Hazards Caused by H₂S at Water Treatment Facilities
If left unmanaged and unaddressed, the presence of H₂S can lead to a range of problems for project teams, the facilities themselves and the communities they serve. The main hazards to be aware of include:
Personal Health and Safety
H₂S has toxic properties and exposure of any kind can present a health hazard. For workers exposed to larger quantities, risks can fall anywhere between minor ailments such as eye and skin irritation right through to respiratory issues, neurological effects and even death through inhalation.
This tragic, recent case[1] shows just how risky H₂S can be.
Environmental Health and Safety
A significant build-up of H₂S is highly flammable and can form explosive mixtures with air when in a range of approximately 4.3% to 46% by volume. When a project takes place in a confined space or environment where H₂S is high (such as a sewer or tank) and there is limited access to fresh air to dilute the compound, the environment becomes potentially explosive. Extra measures may need to be taken to make the working environment safe again.
Corrosivity
H₂S has an acidic byproduct which can degrade the infrastructure of water treatment systems such as storage tanks, pipes and pumps over time if not carefully managed. This and can mean costly repairs and maintenance are required more often and cause physical danger should supporting structures fail whilst works take place.
Local Impact
It may seem like a small inconvenience when compared with other risks, but the smell caused by a build up of H₂S can be a real nuisance for local communities, businesses and neighbours, especially if this is a regular or long-term occurrence.
Drinking Water Safety
High concentrations can contaminate water sources, affecting quality of the drinking water and health of aquatic ecosystems. Effective management and monitoring of H₂S levels are crucial for maintaining the integrity of water systems and ensuring public safety.
Regulations
Organisations that oversee water and wastewater treatment facilities must meet extremely strict guidelines set by governing bodies. Failing to adequately manage H₂S levels can result in legal penalties, fines and reputational damage.
Water Sector Projects and H₂S Exposure Limits
Water sector workers, particularly those working in sewage treatment, wastewater management and workers in the oil and gas industry can find themselves at increased risk of significant H₂S exposure.
In the UK, H₂S is covered by Workplace Exposure Limits (WELs) under the Control of Substances Hazardous to Health (COSHH) regulations. These are set by the Health and Safety Executive (HSE) to protect workers from over exposure to hazardous substances like H₂S which are linked to causing serious health issues.
For H₂S, the long-term exposure limit (8-hour time-weighted average) is set at 5 ppm and the short-term exposure limit (15 minutes) is set at 10 ppm[2]. These limits are designed to ensure that workers are not exposed to levels that could cause adverse health effects and it’s important that employers monitor and control H₂S exposure in the workplace to maintain a safe working environment.
How to Keep Water Sector Workers Safe in an Environment with H₂S
Gas Monitoring
Personal gas monitoring equipment for workers entering a space with potentially high levels of H₂S means that workers can focus on the job at hand, safe in the knowledge they will be alerted if exposure levels become too high.
RVT Group offer two portable gas monitors, the MONITEX® 4 Gas Monitor and MONITEX® P-PID Portable Gas Monitor benefit from:
Ventilation
For working environments with particularly high volumes of H₂S, it may sometimes be more appropriate to force fresh air into the space for the duration of the project. This not only helps to dilute pockets where H₂S is built up, but also helps maintain adequate air quality in a space.
RVT Group offer a wide range of temporary ventilation fans, the product best suited to your project will depend on a number of factors such as size of the working area, distance from the nearest fresh air source, if the environment is potentially explosive etc. Our fans benefit from airflows of up to 120,000m³/h and fall under one of the following categories:
The key take away from this article is that over exposure to H₂S can be significantly damaging to an individual’s health but, there are simple, practical steps that can be taken to ensure projects remain compliant and teams remain healthy.
By implementing suitable health hazard controls, it allows your team to focus on the task at hand. The most crucial step when implementing hazard controls, is ensuring they’re the right measures for the space and activities taking place and RVT Group are here to help.
Whether it is carrying out a free hazard control assessment to determine the equipment to best protect your team or simply providing you with a quote for specific engineering controls you have in mind, support is just a short form away >
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