The document describes ETC catalytic air treatment systems for producing oil-free compressed air. ETC systems use catalytic oxidation to convert oil and hydrocarbons in compressed air into water and CO2, continuously producing Class 0 compressed air according to industry standards with residual oil content less than 0.0025 mg/Nm3. ETC systems offer guaranteed oil-free air quality for 20,000 hours of operation without risk of saturation from hydrocarbon compounds. The systems can treat air with up to 200 mg/Nm3 of oil and produce clean condensate.