Superior 30-day performance with consistent fragrance release for day 1 to day 30. Easy to refill. Hang approximately 6' high in the center of the space; no need for a ladder. Light activated, only runs when the lights are on. Requires one C alkaline battery. Removing the battery starts the program over at day one. Green light blinks every 15 seconds when fan is running, Red light blinks when battery is low or on day 30. The word 'Replace' flashes on day 30. An audible beep begins on day 33 if the refill and battery have not been replaced.