Introduction
The oil and gas industry are no stranger to hazardous gases, but few are as dangerous as hydrogen sulphide (H2S). Known for its distinct “rotten egg” smell, H2S is a silent killer—highly toxic, flammable, and capable of causing fatalities within seconds at high concentrations.
Whether you’re an industry professional, safety officer, or someone working around gas fields, understanding how H2S exposure affects workers and how to mitigate risks is crucial. This guide breaks down everything you need to know about H2S in the gas industry.
What is Hydrogen Sulphide (H2S)?
Hydrogen sulphide is a colourless, highly toxic, and flammable gas that occurs naturally in crude oil, natural gas, and volcanic emissions. It is also produced during the breakdown of organic matter, such as in sewage and swamps.
Key Characteristics of H2S:
- Chemical formula: H2S
- Smell: Rotten egg (but can become odourless at high concentrations due to olfactory fatigue)
- Flammability: Highly flammable and explosive when mixed with air
- Solubility: Soluble in water, forming weak hydro sulphuric acid
How toxic is Hydrogen Sulphide?
H2S is extremely toxic, even in small concentrations. The Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) set strict exposure limits for worker safety.
Hydrogen Sulphide Exposure Limits:
| Concentration (ppm) | Effects on Humans |
| 0.01 – 0.3 ppm | Detectable odour |
| 10 ppm | Irritation of eyes, nose, throat |
| 50 – 100 ppm | Severe eye and respiratory irritation |
| 200 – 300 ppm | Pulmonary edema, loss of consciousness |
| 500 – 1000 ppm | Immediate collapse, respiratory failure, death |
At above 700 ppm, a single breath of H2S can cause instant unconsciousness and death within minutes.
Sources of H2S in the Gas Industry
H2S is commonly found in:
- Natural gas fields: High concentrations in sour gas reservoirs
- Oil refineries: Present in crude oil processing
- Drilling operations: Released from underground formations
- Storage tanks & pipelines: Accumulated in confined spaces
- Sewage & wastewater treatment: A by-product of decomposition
Since it can accumulate in enclosed areas, H2S poses serious risks for workers in confined spaces.
The Dangers of Hydrogen Sulphide Poisoning
H2S poisoning occurs when workers inhale even small amounts of the gas. The severity of symptoms depends on the concentration and duration of exposure.
Short-Term (Acute) Effects
- Dizziness
- Nausea
- Eye and throat irritation
- Loss of smell at high levels (olfactory fatigue)
- Unconsciousness
Long-Term (Chronic) Effects
- Neurological damage
- Memory loss
- Respiratory issues
- Cardiovascular problems
In worst cases, exposure can cause death in seconds due to respiratory paralysis.
Safety Measures to Prevent H2S Exposure
Engineering Controls
- Ventilation systems to prevent gas accumulation
- Automated H2S monitoring to detect leaks
- Gas scrubbing to remove H2S from sour gas
Personal Protective Equipment (PPE)
- Self-contained breathing apparatus (SCBA) for high-risk areas
- H2S-resistant suits and gloves for exposure protection
Training & Emergency Preparedness
- H2S safety training for all workers
- Evacuation drills and emergency response plans
- First aid training for H2S poisoning incidents
What to Do in Case of H2S Exposure?
If someone is exposed to H2S:
- Move them to fresh air immediately.
- Administer oxygen if they are having trouble breathing.
- Call emergency medical services (DO NOT attempt CPR in a contaminated area!).
- Use full respiratory protection before attempting a rescue in high-H2S areas.
Conclusion
So, is hydrogen sulphide poisonous in the gas industry? Absolutely! H2S is a deadly gas that poses serious health hazards, explosion risks, and immediate fatality dangers when not properly managed.
The key to preventing H2S-related accidents is strict safety protocols, continuous monitoring, and proper training. Companies must invest in detection systems, PPE, and emergency preparedness to keep workers safe.
By staying vigilant and proactive, the oil and gas industry can minimise risks and prevent tragic incidents caused by H2S exposure.
Frequently Asked Questions (FAQs)
Can you smell hydrogen sulphide at dangerous levels?
No. While H2S has a rotten egg smell at low levels, your nose cannot detect it at high concentrations due to olfactory fatigue.
What is the lethal concentration of H2S?
At 500-1000 ppm, exposure can cause instant unconsciousness and death.
How do gas workers protect themselves from H2S?
Workers rely on gas monitors, proper PPE (SCBA), ventilation systems, and emergency training to stay safe.
Gas Detectors that Detect H2S
Rockall Safety have a range of H2S gas detectors available, including:
