On completion of the online H2S Awareness training course learners will know;

• Why H2S is highly dangerous
• The risks to health associated with H₂S
• Understand where H₂S can be found
• The workplace exposure limits (WEL)
• Personal Safety Measures
• Team Safety Considerations

• Invisible – Hydrogen sulphide is a colourless gas
• Odorous  – Hydrogen sulphide is a flammable, colourless gas with a characteristic odour of rotten eggs.
• Density  – Hydrogen sulphide is heavier than air and may travel along the ground. It collects in low-lying and enclosed, poorly-ventilated areas such as basements, manholes, sewer lines, under- ground telephone vaults and manure pits.  Most deaths occur in confined spaces.
• Toxic  –  Gas burns and produces other toxic vapours and gases, that can cause death within a short space of time
• Explosive  –  H₂S has a lower explosive limit LEL of 4.3% and an upper explosive limit UEL of 46%

In the UK there are 2 Workplace Exposure Limits defined.  Long-term exposure limited is 5ppm.  Short-term exposure limit is 10ppm.

Short-term symptoms of H2S exposure at various concentrations are shown below:

• 0.01-1.5 ppm:
  • Rotten egg smell is first noticeable to some. The odour becomes more offensive at 3-5 ppm.
• 2-5 ppm:
  • Prolonged exposure may cause nausea, tearing of the eyes, headaches or loss of sleep. Airway problems in some asthma patients.

5ppm is the UK long-term exposure limit.  10ppm is the short-term (15 mins) exposure limit.

• 20 ppm:
  • Possible fatigue, loss of appetite, headache, irritability, poor memory, dizziness.
• 100 ppm:
  • Coughing, eye irritation, loss of smell after 2-15 minutes.  Altered breathing, drowsiness after 15-30 minutes. Throat irritation after 1 hour. Gradual increase in severity of symptoms over several hours. Death may occur after 48 hours.
• 200-300 ppm:
  • Marked conjunctivitis and respiratory tract irritation after 1 hour. Pulmonary edema may occur from prolonged exposure.
• 500-700 ppm:
  • Staggering, collapse in 5 minutes. Serious damage to the eyes in 30 minutes. Death after 30-60 minutes.
• 700-1000 ppm:
  • Rapid unconsciousness, “knockdown” or immediate collapse within 1 to 2 breaths, breathing stops, death within minutes.
• 1000-2000 ppm:
  • Nearly instant death

Hydrogen Sulphide gas is commonly found during the drilling and production of crude oil and natural gas, plus in wastewater treatment and utility facilities and sewers.

However, H₂S is a potential hazard in a wide range of industries and work environments, including, but not limited to:

• Animal fat and oil processing
• Asphalt storage
• Blast furnaces
• Breweries and fermentation processes
• Chemical production (including phosphate purification, hydrochloric acid purification, cellophane, rubber, plastics, soap, silk, photoengraving, glues, textile printing, etc)
• Clean-up activities of organic/sulphur containing slurry/sludge
• Coal gasification plants
• Coke ovens
• Farms and livestock operations
• Fertiliser production
• Fishing vessel holds
• Geothermal plants and utilities
• Landfills of municipal/farm/organic waste
• Metal processing
• Oil and gas (including crude oil refineries, handling plants and pipelines)
• Pulp and paper production
• Sewage treatment plants
• Slaughterhouses and rendering plants
• Sugar production
• Sulphur and hydrogen sulphide production
• Tanneries
• Waste treatment operations

References [External Links]

1. UK HSE list of 500 hazardous substances and their exposure limits – Link
2. UK HSE Hydrogen Sulphide general information – Link