The compression process increases the concentration of solid particles suspended in the atmosphere, generated by natural phenomena but also by polluting agents or industrial processes. Water, oil, impurities and odours cause alterations in the quality of the air produced, corrosion of the pipes and damage to the pneumatic equipment, thus negatively affecting performance. 
Inside 100 m3 of compressed air, there are*: 2.2 litres of water (75% in liquid form and 25% in gaseous form) 2 grams of oil, 8 million solid particles and odours, determined by the compression process but mainly by the environment in which the compressor sucks air. Some production processes do not tolerate the presence of these substances.