In Atlas Copco’s AQ compressors water is used as lubricant, and at the same time it seals and cools the compression element. Through its superior cooling capability, water ensures low operating temperatures, and the AQ is more energy efficient than other oil-free compressor technologies. Warm water, however, means also bacteria growth, corrosion and scaling, and for this reason distilled water is used for start-up; the water supply is then maintained through a “reverse osmosis” membrane that filters out particles and minerals. To prevent bacteria and minerals from accumulating, the AQ compressor is regularly and automatically flushed, ensuring reliable water quality at all times. Also the cooling system of the integrated dryer and the aftercooler maintain the water quality in the same way. The AQ screws are made from a ceramic and polymeric material, the shaft from stainless steel and its casing in an aluminum and bronze alloy. AQ compressors are certified by an independent third party organization that performed tests in extreme conditions, and even simulated component failures and with different types of bacteria. The risk of contamination of the compressed air proved to be extremely low even in presence of a very high bacterial concentration.