Pre-filters should be checked weekly for any dust or dirt build up and cleaned when necessary. Remove all four filters by pressing the small clip button at the top and lifting them up. If possible, shake dust off outdoors. Use a vacuum cleaner or dry cloth to remove finer dust. If needed, use mild soap and water to wash them. Make sure the filters are completely dry before re-inserting them. The HEPA filter and UVC light requires service after 9,000 hours (approximately 1 year of continuous runtime). Your Rensair will automatically alert you when the parts need to be replaced via the ‘service indicator’ on the display. Changing the HEPA filter is a simple process and described in the instruction manual, but if any assistance is required, our technicians are always willing to help.