The final post filter is either an F9 or HEPA, depending on the application and all three filter stages are held in place with positive clamping technology to prevent by-pass of the filters. Filter gauges with ‘filter full’ indicators are fitted as standard and cover all three stages. To meet the low maintenance requirement stipulated by the customer, the Handte EM Profi 1.8 was fitted with a unique, patented, automatic, in-situ Demister cleaning system which uses clean coolant or water. A spray nozzle is located in the inlet duct elbow, above the first Demister and activated by a signal to a solenoid valve. The valve opens, and the cleaning medium is sprayed into the Demisters for a set period of time, during normal operation, with the unit’s fan running. This ensures there is no downtime which is associated with other manual filter cleaning methods. Any collected coolant and cleaning medium can be returned to the machine tool sump for re-use or to a container for disposal. On larger Handte EM Profi units a pump can be supplied to return the collected coolant to a point further away from the unit. Filter life of up to five years for the Demister stages and one year for the post filter means that the unit can operate virtually maintenance free.