A humidistat is a device used to measure and regulate the humidity in a room or building. It is commonly used in HVAC (heating, ventilation, and air conditioning) systems to maintain a comfortable humidity level. The humidistat works by sensing the humidity in the air and then controlling the HVAC system to either increase or decrease the humidity level as needed. The humidistat can be set to a specific humidity level and will automatically adjust the HVAC system to maintain that level. This helps to ensure that the air in the building is not too dry or too humid, which can be uncomfortable and can also cause damage to the building. A humidistat is an important part of any HVAC system and can help to ensure that the air in the building is comfortable and safe.