Extech's RH35 monitors Humidity, Temperature, and Dew Point for the previous 24 hours and alerts users to indoor mold hazard conditions starting with a frown icon warning when humidity reaches 60%RH. When the RH exceeds 65%, a loud audible alarm and bright flashing red LED will be triggered. The frown icon will also appear if the environment is too dry (<40%RH) where static electricity becomes a concern. The RH35 is perfect for commercial, retail and residential sites prone to mold. Complete with stand and 2 AAA batteries.