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 percent RH. When the RH exceeds 65 Percent, a loud audible alarm and bright flashing red LED will be triggered. The frown icon will also appear if the environment is too dry where static electricity becomes a concern. The RH35 is perfect for commercial, retail and residential sites prone to mold. Complete with stand and batteries.