Humidity levels above 20 percent help prevent dry, sore throats and should make the air feel warmer and more comfortable. Moist air will also eliminate static electricity in the house and help to protect plants and preserve your furniture.

On the other hand, humidity levels above 40 percent can cause frosting and fogging of windows,

staining of walls and ceilings, peeling paint, mould growth and odours. When relative humidity is more than 50 percent, airborne diseases become more difficult to control.

Condensation on windows or static electricity can provide good indications of the relative humidity levels. However, a humidity sensor or humidistat can monitor or adjust humidity levels more accurately.