Comfort
The correct level of humidity in a room affects our perception of comfort and reduces the risk of respiratory illness. On hot days, if humidity levels are too high, our bodies are less efficient at cooling and we are therefore uncomfortable. If humidity levels are too low then we tend to suffer more discomfort from dry throats and sore eyes. In addition, bacteria and viruses are spread more easily and our perception of temperature is considerably cooler. The heating systems used to increase indoor temperatures in winter also tend to reduce the relative humidity of the air, meaning that low humidity is a problem particularly during the winter months.

Health
Controlling humidity levels helps prevent the growth and diffusion of mites, mould, bacteria and viruses. It also helps avoid extreme dryness. The drying of mucous and the decreased protection of a person’s airways can result in respiratory infections, allergic rhinitis and asthma. Humidity control can also significantly reduce dustiness.

Manufacturing & storage
Hygroscopic materials absorb or give off moisture to their surroundings. Materials such as textiles, wood, paper and foodstuffs are more likely to change dimensions due to variations in humidity than temperature. In order to guarantee high precision, reliability and quality, proper control of the humidity level is required. The correct and constant level of humidity over time reduces the dryness of the materials and substances used in manufacturing processes, prevents weakening and changes to the mechanical characteristics, and eliminates adhesion and electrostatic discharges.

Static electricity
Static electricity is reduced significantly when relative humidity is maintained above 35%. Humidity levels above 40% produce a very thin film of liquid on the surfaces of objects, and this film is sufficiently conductive to discharge any electrostatic charge as it is produced, thereby preventing the creation of high potential. There are many sectors of industry that are especially sensitive to this problem, as are electronic devices, such as computers, which can be damaged by electrostatic discharges.