Hydrogen sulfide is a toxic gas producing manifold effect. It is colorless gas with unpleasant odour of bad eggs. In nature large amounts are produced during processes of biological decomposition. A major part of the atmospheric hydrogen sulfide is of natural geothermal origin. Air pollution is of anthropogenous type as well. Industry is the main source - coke ovens, cellulose production, artificial fibers, natural gas and oil-product refining.

Impact on human health
Contact of man with this gas is effected through the respiratory system. Scanty information exists on possible penetration through the digestive tract. The gas is absorbed by the organism through the lungs. In the liver and kidneys it is transformed into tiosulfates and sulfates. It is eliminated through the lungs, urine and fecal matter. Health effects are as follows - low concentrations may irritate the mucous tissues and cause conjunctivitis, and high concentrations may cause serious damages of the respiratory organs.
Continuous exposure to high concentration should be avoided.
It is established that hydrogen sulfide concentrations which cause olfactory discomfort are much lower than those representing health risk. Hydrogen sulfide concentrations between 0.2 and 2.0 g/m3 are considered to represent olfactory risk, but more serious complaints occur at concentrations above 7 g/m3. The lowest short-term exposure level causing unfavorable health effect, namely eye irritation, is 15 - 30 mg/m3. Graver eye damage is witnessed at 70 - 140 mg/m3. Very high hydrogen sulfide concentrations (above 400 mg/m3) may cause lung damage. Continuous exposure to high concentrations may disturb blood pigment formation and damage the central nervous system (CNS). The assumed limit value is based on its sensor effect.

The following limit values for hydrogen sulfide content in the atmospheric air are set by our legislation Regulation No. 14 (State Gazette No. 88/1997, amended SG No. 46/1999, amended and supplemented, SG No. 8/2002): - 1-hour LV (for 60 minute exposure) - 0,005 mg/m3;
- 24 hour average LV (for 24-hour exposure) - 0,003 mg/m3.