The room hygrometer is a device used to measure humidity. It is also commonly used to measure temperature. Air humidity is an important factor in many fields, such as agriculture, construction, heating, ventilation, air conditioning (HVAC), etc. If the humidity indoors is very high, mold can appear. Some types of mold cause respiratory problems and other health effects for people living or working in the environment. Additionally, mold that has penetrated the walls or ceiling of a building must be removed for safety reasons.