2. Sources

The air we breathe contains sulfur compounds produced by natural processes (volcanoes, fumaroles, aerobic or anaerobic fermentation, etc.) and human activities. The table 4 shows some of the concentrations of sulfur compounds found in the residual background in the air. These levels are very low. · It is worth noting the seemingly large number of molecules inhaled with each breath. This value should be put into perspective by considering Avogadro's number (6.02 × 10 ²³ molecules/mol).