Auxiliary equipment It is easy to expand an installation with numerous pieces of auxiliary equipment to, for example, increase the air quality or monitor the system. However, even auxiliary equipment needs service and brings about costs for maintenance, e.g. in the form of filter replacement, drying agent replacement, adaptation to other equipment and the training of staff. In addition there are secondary maintenance costs, for example, the distribution network and production machines, which are affected by the quality of the compressed air and deposit costs for oil and filter cartridges. All of these costs must be evaluated in the calculation that forms the basis of an investment.