The comfort level differs among people, but most individuals feel most comfortable in an environment with a relative humidity (RH) between 40-60 percent. However, the relative humidity (RH) of your interior space generally should be between 30-50 percent. Most dehumidifiers come equipped with a humidistat that enables the user to regulate a desired RH.
Bacteria and fungus thrive in environments with an RH above 50 percent, which is particularly unhealthy for those who suffer from allergies.
During winter months when a furnace is operating, an RH above 40 percent can cause window condensation. An RH below 30 percent can cause dehydration and overly dry skin. An arid environment also creates a great deal of static electricity.