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MSA Safety answers some common questions about hydrogen sulphide gas (H2S), and the differences between low and high concentrations

Hydrogen sulfide (H2S) gas can be fatal at high concentrations. But even low concentrations can cause health issues, particularly with prolonged exposure. So how can you best protect workers and minimise downtime?

What is H2S gas?

Hydrogen sulfide is a highly flammable, toxic and corrosive gas found in several industries including oil and gas, wastewater and chemical processing. It’s sometimes called ‘sour gas’, ‘sewer gas’ or ‘stink damp’ because of the way it smells like rotten eggs. However, H2S can’t reliably be detected by smell as it quickly deadens the sense of smell (a process known as ‘olfactory desensitisation or fatigue’).

How dangerous is H2S?

Exposure to high levels of H2S can be fatal, leading to loss of breathing, coma, seizures and death. It’s the second most common cause of fatal gas inhalation exposure in the workplace, second only to carbon monoxide.
H2S can also be harmful at low concentration levels, causing headaches, dizziness, nausea, breathing difficulties and a sore throat. These health impacts can become more serious with prolonged exposure.

Low concentration vs. high concentration H2S – exposure limits

The health impacts of H2S depend on how much is inhaled and for how long. The recommended exposure limit set by NIOSH (the US National Institute for Occupational Safety and Health) for ten minutes is 10 ppm. However, some U.S. states have developed ambient air standards for H2S well below OSHA and NIOSH standards due to concerns about health risks from chronic exposure.

For longer exposures to H2S, the recommended limits are much lower. For example, if you’re exposed for up to 24 hours, the World Health Organisation (WHO) recommends a maximum exposure of 0.1 ppm.
In response to concerns about the risks of H2S to human health even at low concentration levels, some countries have introduced equally stringent guidelines requiring businesses to monitor H2S at such concentrations. That’s why we’ve recently updated our ALTAIR io™ 4 Connected Gas Detector, offering the option of a low-concentration hydrogen sulfide sensor that can detect H2S at very low levels.

H2S in industry – the different sector impacts

H2S creates safety challenges for many industries. But some industries are more likely to be affected. These include:

Oil, Gas & Petrochemical

Oil, gas and petrochemical facilities handle raw ‘sour’ gas and oil which are naturally high in H2S. Extraction and refining processes release H2S, which may accumulate in confined, poorly ventilated spaces like processing units, pipelines and storage tanks. Closed systems with high-pressure conditions amplify the risks for workers.

Balancing safety and operational efficiency is an ongoing challenge in the oil, gas and petrochemical industry. Some are tackling this challenge by integrating new technological solutions into their safety management practices.

Waste water management

Wastewater facilities such as closed pipelines and sludge tanks have low oxygen levels and so provide the ideal conditions for H2S buildup. One of the key risks for wastewater workers is when they are entering confined spaces such as tanks and sewer lines. For many waste water management businesses, real-time monitoring of gas levels is considered a must-have.

Steel production

The steel industry’s use of high-temperature processes and sulfur-rich materials can lead to the release of H2S, creating hazards for workers. Confined, poorly ventilated spaces and desulfurisation units pose particular risks.

Preventative measures – safeguarding workers

Given the well-documented risks of H2S to workers, safety managers are seeking out effective preventative measures, including regular training and effective ventilation. The use of Personal Protective Equipment is also important.

A particularly helpful method for avoiding excessive H2S exposure is constant monitoring by advanced gas detection systems such as our ALTAIR io 4 Connected Gas Detector. Such systems can give you an early warning of even subtle increases in H2S concentration, helping you stay ahead of potential risks. Our updated ALTAIR io 4 device can detect subtle changes in H2S concentration levels at a resolution of 0.1 ppm, offering enhanced protection to workers. The default configuration for low-concentration H2S detection starts at 0.3 ppm, but customers may choose to configure the device to detect H2S starting at 0.0 ppm. This capability is particularly important in industries like oil and gas where companies wish to monitor low levels of H2S. Our low-concentration H2S sensor also offers processes designed to streamline regulatory compliance, minimising downtime and allowing readiness even for large-scale operations.

As with all toxic gases, early detection of H2S is an excellent way to alert safety managers to small increases in H2S emissions so they can help workers avoid harmful exposure, even at low concentrations.

Methane can be liquefied and transported at extremely low temperatures as LNG. (Image source: Adobe Stock)

MSA Safety has some advice for navigating the hazards of methane gas leaks

Methane (CH₄) is a simple hydrocarbon and the primary component of natural gas. Colourless and odourless, it possesses several key properties that make it both a valuable resource and a potential hazard. Strict safety measures and protocols are needed to manage the risks associated with methane’s high energy content and the extreme conditions required to keep it in liquid form.

The explosive hazards of methane gas leaks

Methane, being a highly combustible gas, can form explosive mixtures with air in concentrations ranging from 5% to 15%. This property, combined with its odourless nature, underlines the need for vigilance in detecting leaks before they escalate into dangerous situations. When leaked into confined spaces, such as buildings or pipelines, methane can create an explosive atmosphere, where even a small spark or ignition source can trigger an explosion.

The physical state of methane as a colourless and odourless gas at room temperature and atmospheric pressure makes it difficult to detect without specialised equipment. Methane leaks in pipelines, storage facilities, or other infrastructure can result from corrosion, equipment malfunctions, or inadequate maintenance. These leaks not only release methane into the atmosphere but also expose these facilities to the risk of explosions.

Methane can be liquefied and transported at extremely low temperatures as LNG, a critical component of the global energy industry and an important energy transition fuel. The transportation and storage of LNG come with their own set of specific and unique hazards.

Preventing methane gas leaks

Effective detection methods and preventive measures can mitigate the unique hazards associated with both gaseous and liquefied methane, particularly in confined spaces and during LNG transport and store.

1. Inspection and maintenance:

Regular inspections can help to identify potential vulnerabilities in infrastructure, such as corroded pipes or faulty equipment.

2. Enhanced leak detection technologies:

Utilizing cutting-edge technologies, including advanced gas sensors, can improve the detection of methane leaks before they escalate.

3. Emergency shutdown systems:

Implementing robust emergency shutdown systems in infrastructure can swiftly isolate and contain methane leaks in the event of detection.

4. Public awareness and preparedness:

The addition of odorants like mercaptan to natural gas, plays an important role in public safety. Public awareness campaigns, coupled with clear guidance on emergency response procedures, further enhance community preparedness against the explosive hazards of methane leaks.

Gas monitoring methods for methane leaks

Detecting methane gas leaks can help to avoid environmental hazards and potential explosive situations. Several methods and technologies are employed for methane leak detection. They include:

• Point detectors: These are fixed devices that can detect methane levels in specific locations where they are installed. They provide real-time readings and are often used in areas with known risks. Infrared and catalytic bead sensors are common detection methods.

• Open path detectors: These devices use infrared technology to detect methane along an open path between a transmitter and a receiver. Changes in the infrared light absorption indicate the presence of methane.

• Acoustic detectors: Acoustic (ultrasonic) sensors can detect the sound of gas escaping from leaks. This method is especially useful for identifying leaks in pressurised systems and can complement other detection methods.

• Fire and gas detection controllers: Used to power the connected methane fire and gas detectors and display measured gas concentrations. They can also monitor the limit values, actuate alarm devices, and initiate risk reduction measures.

Combining multiple detection methods can provide a more comprehensive and reliable approach to identifying and addressing methane gas leaks promptly. The choice of method often depends on factors such as the size of the area to be monitored, accessibility, and the severity of potential risks.

Understanding the unique properties of methane, from its chemical composition to physical characteristics, underscores the explosive dangers associated with gas leaks. By combining rigorous inspection, advanced detection technologies, emergency shutdown systems, and community education, risks can be mitigated, helping to ensure a safer and more secure future for all.

Find out more at https://gb.msasafety.com/submarket/oilandgas-lng

The programme is designed to elevate workplace safety, minimise incidents, and cultivate a culture of safety excellence. (Image source: SafeStart)

A new year brings new opportunities, and there’s no better time to start rethinking your personal safety – both on and off the job, says Larry Wilson, Author and CEO, SafeStart

This month, we’re pausing our Paradigm Shifts series to bring you an exciting invitation: join us for the SafeStart Trainer Certification Level 1 Course in Dubai, UAE! This immersive two-day programme is designed to elevate workplace safety, minimise incidents, and cultivate a culture of safety excellence. You’ll gain valuable insights and practical tools to effectively implement the SafeStart process and become a certified trainer.

Event Details

Date: 18–19 February 2025
Time: 8:00 AM – 4:00 PM
Location: Media Rotana, Hessa Street, Dubai, UAE

What is SafeStart?

SafeStart is a globally renowned safety program that helps organisations reduce workplace incidents by addressing human factors, critical errors, and decision-making risks. This Level 1 certification will guide you through SafeStart’s six-step process, enabling you to drive long-term cultural change and boost performance.

Explore the agenda highlights here.

Don’t miss this opportunity – spaces are limited, so secure your place today!

Looking forward to seeing you in Dubai!

Warm regards,
Larry Wilson
SafeStart Author and CEO

Figuring out when an incident will take place will be important. (Image source: Canva)

Larry Wilson, Author and CEO, SafeStart, emphasises the critical importance of identifying "when" we're most vulnerable to complacency and critical errors. Read on:

As we keep exploring the series Paradigm Shifts in Safety, we’re excited for you to check out the eighth article in this 12-part series.

Lots of ground covered so far: hazardous energy and movement, three sources of unexpected events (over 95% in the Self-Area), the counter-intuitive nature of dangerous activities vs. actual outcomes and then why: because when both our eyes and mind are not on task, for that moment, we are defenseless.

So as mentioned in an earlier article, it’s not that we are totally defenseless, it’s that from time to time, we are “momentarily defenseless”. which is why you hear so many people talking about car wrecks or serious injuries, saying that I really wasn’t doing anything wrong, I wasn’t really speeding or rushing. Okay, I was a bit tired and I was thinking about a problem at work, or home, or whatever… and then (car wreck, bad fall, serious cut, blown knee, concussion, etc.).

So, figuring out “when”, becomes the crux of the matter. Unless we know when those moments will happen, knowing why we get hurt badly (eyes and mind not on task/no reflex) won’t help to prevent the next one. So, figuring out the “when” part is the key. And unfortunately, for so many years, the focus has been on “what” the people were doing and how much hazardous energy they were dealing with (which is important) but not, which is the main paradigm shift here, not nearly as important as figuring out when.

When will you or me or the next guy in line— when will we be most likely to make both critical errors at the same time—where there is also a significant amount of hazardous energy involved?

Well… it will likely be doing something that you have been doing for a while, because at the beginning of any activity where there is a fair bit of hazardous energy and the potential for injury – “awareness“ or “eyes and mind on task” – is very high (see Figure #1).

During this first period with an activity or skill it is possible and normally quite natural to self-trigger or to be able to self-trigger on the amount of hazardous energy. And as a result, it’s easy to stay focused. It may even seem, at least when you first start out, that it would be impossible to become complacent.

However, as we all know, the initial fear rarely lasts forever. And over a period of time, depending on the activity or skill required, we come to the first stage of complacency. This is where the fear or skill is no longer pre-occupying.

And as mentioned in previous articles, we don’t give our minds permission to wander. It happens without our permission or without making a decision to think about something else (Figure #1). So even if you don’t have anything else you need to think about or want to think about, your mind can still drift away.

But if you’re rushing, chances are it’s for a reason. It might be because you want to get there early. More likely, it’s because you don’t want to be late. Either way, that’s what most people think about when they’re rushing—not what is the risk in the moment – right now (driving really fast on a city street). And if the consequences for being late are going to be really bad (late for meeting at work)…

Click here for the full article and to learn why understanding when moments of vulnerability occur is key to prevention, not just focusing on what we’re doing. Discover how to shift your perspective and enhance your safety strategies: https://ae.safestart.com/paradigm-shifts/8-the-complacency-continuum-and-when-vs-what/