BestAir Hygrometer Humidity Monitor with Optimal Comfort Zone Display – Quantity of 4 . High humidity levels in your home can cause discomfort you and your family as well as potential damage to certain areas in your home. The BestAir Hygrometer Humidity monitor is designed to allow you to get accurate humidity readings in your home. It works with any brand of humidifier and will accurately measure the air humidity level in your home and provides an easy-to-read display for the optimal comfort zone without the need for batteries.