FACT #1 - hydrogen sulfide, a chemical compound, H2S, a colorless, extremely poisonous gas that has a very disagreeable odor. Much like that of rotten eggs.
FACT #2 - Hydrogen sulfide is flammable; in an excess of air it burns to form sulfur dioxide and water, but if not enough oxygen is present, it forms elemental sulfur and water.
FACT #3 - Hydrogen Sulfide is part of many unrefined carbonaceous fuels, e.g., natural gas, crude oil, and coal; it is obtained as a byproduct of refining such fuels.
FACT #4 - The bacterial breakdown of organic matters like human and animal wastes found commonly in sewages also produces Hydrogen sulfide.
FACT #5 - It is a chemical asphyxiant like carbon monoxide. Depending on the concentration of the gas, people might exhibit varying symptoms. As Hydrogen sulfide affects the absorption of oxygen, it restricts cellular respiration which can lead to bronchitis and edema in long term exposures.
FACT #6 - At 0-10 ppm : Irritation of throat, eyes and nose leading to watery eyes and nose.
FACT #7 - At 10-50ppm: causes headaches, dizziness and nausea.
FACT #8 - At 50-220ppm: Respiratory tract can get irritated, convulsions, can be serious and even fatal in very severe cases.