Studies show that when room RH drops below 40 percent, incidents of respiratory illness increase. Proper humidification can significantly reduce student and employee absenteeism. Controlling a building`s RH significantly improves production processes. RH affects the moisture content of hygroscopic materials, such as wood, textiles, paper, leather, fibers, and foods. Such materials either absorb or release moisture until an equilibrium moisture content is reached, which may affect many of the properties critical for production. Preserve materials and artifacts: Fluctuating RH causes material to repeatedly absorb and release moisture. These changes may impact a material`s weight, strength, and appearance, which may damage the material and shorten its longevity.