The new Atlas Copco ZH 355+ - 900+ oil-free centrifugal compressor range employs advanced aerodynamics to reduce energy consumption in the core. Coupled with this, all the components of the package are designed based on Computational Flow Dynamic (CFD) analysis to reduce pressure drops in the package. The result is a reduction of specific energy up to 7% at full load compared to the previous model. Inlet guide vanes (IGVs) further reduce energy cost by 9% at part loads as compared to a throttle valve control. Another aspect is the Class 0 certified quality of air. A fail-safe and unique sealing system prevents the possibility of contamination of the air with oil, without the need of any external buffer air. Oil fumes from the gear box are captured by a motorized demister, thus eliminating the risk of ingestion of oil fumes along with the intake air. This safeguards the end product of the customers against oil contamination.