Bacteria and viruses thrive in dry air. A too-dry room can cause that scratchy sore throat to last for days. Keeping RH levels within a range of 40 to 60 percent not only decreases bacteria and viruses in the air, but hinders the development of fungi, mites, chemical interactions, and ozone production. The result is reduced occurrences of allergic rhinitis, respiratory infections, and asthma among building occupants.
In addition, humidified spaces feel warmer and are more comfortable for occupants, especially in cold climates where heating systems run frequently.