H2S-Hydrogen Sulfide.

Hydrogen Sulfide (H₂S) is colorless, highly toxic gas and has distinctive smell of rotten eggs.H2S  occurs naturally in crude petroleum, natural gas,  sour condensate, sewage sludge, volcanic gases, and  sulfur hot springs. It can also produce from bacterial breakdown of organic matter and human and animal wastes.H₂S is heavier than air and may gathers in low areas such as sewers, pits, trenches, tunnels and bottom of storage tanks or vessels.H₂S is highly flammable at concentrations between 4.3% to 46%.

Physical Properties

Colorless (invisible), highly flammable, highly corrosive, irritant to eyes and respiratory system, strong odor of rotten eggs at low concentrations, high concentrations may have no odor; rapidly paralyzes the sense of smell, heavier than air and may settle in to low lying areas, highly reactive in the presence of acids or strong oxidizing agents, soluble in water. H2S burns with a blue flame and producing sulfur dioxide (SO2) which is also a toxic gas.

Health Effect of H₂S

H2S (ppm)	Health Effects
<0.005	Smell threshold
10	Threshold limits value (TLV&TWA) 8hrs/day or 40 hours/week
20-100	Eye and Respiratory system irritation ,Headache, Nausea & Cough
100-150	Severe eye respiratory system irritation. Some possibility of fluid accumulation in the lungs after several hours of exposure.
150	Loss of smell, which can occur immediately.
200-300	Accumulation of fluid in lungs after 1-2 hours of exposure, severe headache and drowsiness.
300-500	May produce unconsciousness and death after 1-4 hours of exposure.
500-700	Dizziness, breathing difficulties after a few minutes of exposure. Breathing will stop and death will result if not rescued promptly. Requires immediate artificial resuscitation
700-1000	Rapidly fatal, death within a few minutes.

First Aid

Do Not Attempt to Rescue if you are not trained or without Proper PPE.

• Remove the victim from gas to fresh air immediately.
• If the victim is not breathing, applying mouth to mouth resuscitation at once.
• If H2S contacts eyes, wash eyes immediately with water
• Remove contaminated clothing and keep the victim warm.
• Call medical assistance