The Ultimate AT is 100% maintenance free. As soon as you plug 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 device emits powerful negative ions to kill bacteria, dust mites, and food smells that may attract pests – but there are no filters that need to be cleaned or changed. You just plug it in and go about your daily life!