Sentinel GPS BHC-1a WM Basic Wall Mount Humidity Controller The BHC-1a Basic Humidity Controller is designed to control fans, dehumidifier, humidifiers, misters and other ventilation equipment in gardens, greenhouses, grow rooms or other environments The BHC-1a can operate in either dehumidification or humidification modes The BHC-1a features a readily visible switch to alternate between dehumidify and humidify settings