The foundation of any purification system is its filtration and of the ten main contaminants found in a compressed air system, filtration is responsible for the treatment of nine of them. Coalescing filters are the most important piece of purification equipment as they reduce six of the ten contaminants and a look in any air compressor room will find a pair of coalescing filters (backed up with dry particulate and oil vapor removal filters).
The most abundant contaminant in any compressed air system is water. This can be in either liquid or vapour form. Atmospheric air is already very wet, and becomes saturated when compressed. This water vapour will condense when the temperature drops, after the compressor, and will damage air receivers, pipework and equipment. For this reason coalescing filters and then dryers are used to remove the bulk of this water.
