Compared to single extraction units, where the mist of a machine tool is extracted and purified by one single mist collector, central extraction systems are clear advantage for extraction and air purifying of multiple machine tools: The individual machine tools are connected via a pipe system with a centralized AFS air purification device . The purified exhaust air can then be blown as exhaust air directly outside or as circulating air back into the hall. Managing the exhaust air and the associated air exchange reduces the relative humidity, heat and odors in the production hall. Alternatively, the purified exhaust air can be routed to an HVAC system with heat recovery. A heat exchanger recovers residual heat from the exhaust air, which is then used to preheat the air supplied from the outside. HVAC systems are also used to condition the hall air. AFS central purifying systems should always be viewed as an integrated approach. This allows the use of additional heat sources, like thermal discharge from compressors, to be integrated into the overall concept.