HOW FELIWAY CLASSIC WORKS: Provides the same calming messages produced by the natural facial pheromone cats mark with and find reassuring. It is scentless, has no affect on humans or other pets, and is proven to reduce cat stress and make them feel better and more comfortable at home. FOR BEST CONSTANT SUPPORT: Use only FELIWAY diffusers with FELIWAY refills. Refills last up to 30 days and should be replaced when empty. The diffuser device should be replaced every 6 months. Best results are seen after 3 to 4 weeks of continuous use though some cats show improvements within the first 7 days. Degree of results may vary. EASY-TO-USE: Plug in an open area where your cat spends the most time. Due to size, it's recommended to use an outlet free of any other devices. Each diffuser covers approximately 700 sq ft. Leave plugged in continuously with 4ft of clearance above. Note: when operating properly, the diffuser device will get warm to the touch in addition to a green indicator light turning on. SAFE VET-RECOMMENDED EXPERTISE: For over 25 years, the range of FELIWAY cat pheromone products have helped more than 14 million cats worldwide, thanks to FELIWAY's expertise in cat stress, and innovation in cat calming. COMFORT REASSURE YOUR CAT: The original vet recommended cat pheromone diffuser, to calm, comfort and reassure your cat at home (diffuser sold separately). With proven results demonstrated in 9 10 cats, help your cat adjust to changes in their environment, and avoid signs of stress like urine spraying, scratching, or hiding. Also recommended when introducing a new cat into your home.