With standard pre and after filters such as particulate filters, water coalecers and oil coalecers the oil content inside the compressed air can be reduced to 0.01 mg/ m³ (0.01 ppm) For applications of EXTREME air quality such as hospital, pharmaceutical industries, or food and beverage industries, the residual oil content may need to be reduced to 0.003 mg/m³ (0.003 ppm). HACT filters such as Hertz activated carbon G series, GO series, F series filters or HACT activated carbon towers are a must for such kind of applications.