Open up the room to a long-lasting scent without a flame, simply put them in a closet or air vent, set it, and forget it until the fragrance is no longer lingering. Each pack of 8 is designed to last about 2 to 4 months, providing a continuous, refreshing aroma. Perfect for enhancing the ambiance of any room, small particle absorbtion, and these air fresheners blend seamlessly with our range of scented candles and aromatherapy products. Change with filter every two months.