Hydrogen sulfide (H2S) is a colourless gas with a characteristic "rotten egg" smell at low concentrations. It is produced naturally by decomposing organic matter and can also occur as a byproduct in industrial processes such as oil and gas extraction, wastewater treatment, and refining. H2S is heavier than air, making it prone to accumulate in low-lying or enclosed spaces.

Dangers of H2S Gas:

1. Toxicity:
   • Low concentrations: Causes irritation to the eyes, nose, and throat, along with nausea and headaches.
   • Moderate concentrations: Can lead to coughing, dizziness, or difficulty breathing.
   • High concentrations: Rapidly paralyzes the respiratory system and central nervous system, potentially causing unconsciousness or death within minutes.
2. Explosiveness:
   H2S is flammable and explosive when mixed with air at concentrations between 4.3% and 46%.
3. Olfactory Fatigue:
   While the gas has a strong smell, prolonged exposure can desensitize the sense of smell, giving a false sense of safety.
4. Corrosiveness:
   H2S can corrode metals, leading to equipment failures that may pose additional hazards in industrial settings.

Safety Measures:

• Use fixed-point gas detectors and portable H2S monitors.
• Ensure adequate ventilation in work areas.
• Implement emergency response plans, including evacuation and first aid protocols.
• Provide appropriate training and PPE, such as breathing apparatus.

H2S is a highly hazardous substance that requires strict control and monitoring to ensure workplace safety.