Observations clearly show drastic increase of greenhouse and acid gases concentrations with great damages to environment. This leads to increasing rain acidity. Acid rains are highly responsible of forests destructions and impoverishing in nutritious substances. The last point affects particularly animals living in corresponding regions. The main pollutants, which acidify the rain are carbon dioxide, sulphur dioxide and nitrogen oxide (NOx). Energy supply industries and transports are the main acid gases producers. Natural gas and petroleum industries have to deal with raw materials containing very high concentrations of both hydrogen sulphide and carbon dioxide. Other sulphur species normally occur in much smaller amounts. Treating processes are needed in order to remove not only H2S and CO2 but also all other sulphur species and prohibited molecules like aromatics. In 1930, R. R. Bottoms originally applied aqueous alkanolamine processes to gas treating. Alkanolamine processes remain the most attractive ones for big treating units whatever the acid gas or aromatic initial content of fluids to be treated due to numerous degrees of freedom allowed. For these reasons our attention will be focused focused on absorption processes with alcanolamine solutions. Several factors influencing solubilities (temperature, pressure, alkanolamine composition, alkanolamine nature, etc ....) will be examined on both experimental and modelling points of view.