Compressed air leaving the compressor contains considerable quantities of water vapour, oil particles. If the untreated air is supplied to distribution lines, then the moisture would condense to liquid water as it gets cooled. The condensed water is a major cause of downtime in compressed air systems as it causes rust, pitting, blockages and freeze ups, which result in component failure and product rejection. The only way to prevent condensation of water in air lines is to lower the dew point of the air in the system. It is less expensive to own and operate an air dryer than to live with the problems.