The compressed and heated air flow is then constrained by the very pipe along which it is travelling, until it enters an area where it can expand, the expansion causes it to cool rapidly and water condensate forms. Thus, any type of filter is an expansion chamber that can permit water condensation to occur. If there is adequate cooling in the after piping prior to reaching the filter, then the amount of water condensate is lessened. Hence the need for a compressor to have not only a fan type pulley that itself keeps the cylinder head and compressed air as cool as possible, but the compressed air needs to be cooled with the aid of a water coil over the side of the boat, lowering it to 10 degrees below ambient if possible, prior to filtration. The air that we breathe is natural, moist and soothing to throat and lungs, and if dried out too much, we would suffer respiratory problems.
Moist air causes metal cylinders to rust.
Diving tanks and storage air receivers have for many years been of mild steel, as have air receivers in compression charging facilities. To minimize the problem of rust contamination of these cylinders and air tools etc, agencies do their best to supply dry air, not considering the unnatural implications for the breather. Certainly water carrying oil vapor needs be separated, as does the oil, as much as possible prior to final filtering. Activated charcoal is manufactured from wood, coal, peat, or coconut husk. The hardest and best, and the best resistant to breaking down into dust, is the coconut fiber.