Depending on the required usage of compressed air, there are different applicable requirements concerning the acceptable quantity of pollutants. The air quality often needs to be improved through drying (to reduce humidity) and filtration (to eliminate oil and other particles). The compressed air quality is divided in different classes that follow an international standard; ISO 8573.1. The European Cooperative Society for pneumatic equipment manufacturers, developed this ISO standard to help classify the content of compressed air, according to the kind of particles it contain: solid particles, water or oil. With this classification, it is possible to analyze, process and offer compressed air of the highest quality.