Compressed air is not pure. The compressed air contains inherent impurities that are detrimental to the end application. Some common contaminants of compressed air are water, dirt, small wear particles, bacteria and sometimes even degraded lubricating oil. All these impurities mix and often form an acidic sludge that might increase the wear and tear of end applications like pneumatic tools, machineries, valves orifices and electro-pneumatic controls like relays. For increased reliability and energy savings, compressed air must be totally clean and dry.