You may also consider if you anticipate changes in your home (moving, renovation, redecorating, arrival of a new pet, arrival of a new family member). Use the diffuser in the room where your cat spends the most time. Plug the diffuser in an electric socket with a minimum clear distance above the diffuser of 5 ft. (The vapor carrying the FELIWAY messages rises in a column of warm air above the diffuser). One diffuser covers up to 700 sq. ft. You may need to use more than one diffuser for a large or multi-floor home. Be sure to replace your diffuser every 6 months and refill vials every 4 weeks. It is recommended to replace the refill every 4 weeks, even if a small amount of liquid remains in the vial (the vial will never be completely empty).