Machines must not contaminate the conveying medium during the working process with oil. In order to provide the proof that Aerzen Blowers and Compressors are on technical top level and are also allowed to be used in the food- and pharmaceutical industry, Aerzener Maschinenfabrik has started in cooperation with TÜV Rheinland a certification procedure for oilfree operation for class 0 acc. to ISO 8573-1. Within this procedure it should be proven for the blower series GM and GL, for the compressor series VML and VM as well as for the new rotary piston machines of the series Delta Hybrid that less than 0,01 milligram of oil-aerosols and oil-steams per cubicmeter in the compressed-air flow can be measured and consequently the limits of the class 0 are fallen below. The corresponding measurements have been carried out on a Delta Blower Unit type GM 60 S, a screw compressor type VM 21 R and a Delta Screw Unit type VML 25 R as well as a Delta Hybrid Unit type D 36 H. The results are as expected: During the measurements oil-contaminations have not been found in a range above class 0. Thus, Aerzen compressed-air is oilfree – guaranteed and certified.