Within a comparative evaluation study at University Hospital CHU in Rennes, two anaesthesia systems, had been compared with regards to halogenated gas consumption. With Perseus A500 the annual consumption of halogenated gas could be reduced by approximately 20%. The all-over quality of the Perseus A500 convinced the team to implement Perseus A500 into clinical routine. The functionalities of the device enabled the team to look at anaesthesia techniques and re-design protective ventilation. Preventive maintenance was reduced from 6h intervention time per year to 2.5 h. Equipment downtime was reduced what improved efficiency in the operating rooms.