The use of catalyst converters allows supplying chemically clean and oil-free air according to the DIN 8573-1 which produces air under class0 and with oil contents less than 0.0025 mg/Nm³ . These Converters are mounted after oil-inject compressors and produce the air with the quality similar to oil-free types with substantially lower price and maintenance charges. For compressed air cleaning, catalysis chemical reaction occurs that splits the oil and other hydrocarbons parts in to carbon dioxide and water. The necessary operating temperature (180 to 200 centigrade degrees) is held by electrical heating. This heating also causes sterilization because of the bacteria destroying. Unlike the oil-free types, the condensate water after these convertors is neutral and without any corrosion properties. Catalyst converter work resource is guaranteed for 20000 hours or 30 months.