Compressing atmospheric air converts it into potential energy which can be stored, distributed, and used as a source of power for pneumatic systems, tools, and processes. Besides nitrogen, oxygen, and other gasses, atmospheric air contains water, hydrocarbon vapor, and solid particulates ranging in size from sub-micron dust to heavy dirt as large as a millimeter. Compressing this mix concentrates solid contaminants and heats the air so that it holds more water vapor. In addition, oil used to lubricate the compressor can enter the air stream as fine mist, aerosol, or vapor. Even air leaving oil-free compressors can pick up oil vapors from atmospheric air and pass them into the air distribution system.
This hot air leaves the compressor via a heat exchanger into the air storage receiver and distribution pipework. As it cools, water and oil vapor condense and turn to liquid or emulsions which can be removed by an efficient condensate management drainage system. However, entrained solid particulates and any remaining water and oil vapor are carried downstream into the distribution system, where the air can pick up more contaminants such as rust and debris from old receivers, treatment equipment, and pipework.