Humidity can be set on a humidifier to anything between 30 percent and 50 percent, with a level between 45 percent and 50 percent considered ideal. When humidity is over 50 percent, bacteria and mold can accumulate. When humidity is below 30 percent, it becomes easier for the flu to spread, and breathing can feel uncomfortable and difficult.
If a humidifier is not used and air is too dry for a long period of time, it can damage the foundation of the house and even furniture and home accessories. When properly used, humidifiers are helpful for adding moisture back to dry air, especially in the wintertime. They can also alleviate symptoms of any kind of respiratory illness or allergy.