The ulimate AT is 100% maintenance free. As soon as you pug the device into your wall, it goes to work for you! there are three blinking lights on the front of the unit that show you each of the technologies are running. tHE ULIMATE AT emits powerful negative lons to kill bacteria, dust mites and food smells that may attract pests, but thre are no filters that need to be cleaned or changed. you just plug it in and go.