What's so important about the relative humidity inside my home?
Molds, dust mites, bacteria, viruses, and other harmful microbials thrive when the relative humidity in your home or building exceeds 50-55%. These indoor pollutants can be harmful to your family members, particularly those with allergies or other sensitive health issues.
If you suspect high humidity, and/or problems with mold/dust mites/etc., then a humidity sensor is critical.
Measuring the relative humidity in your home will tell you where the problem areas are, and whether your moisture-reduction and control strategies are effective.
The construction of a home also influences how much humidity is desirable. Tightly constructed buildings with properly installed vapor barriers and tight fitting doors and windows retain more heat and moisture. This is where mechanical ventilation becomes important. If a home does not have the proper mechanical ventilation, excess water vapor can move through walls and ceilings, causing wet insulation, peeling paint, and mold on walls and woodwork. Indoor relative humidity above 60% for several hours in an air conditioned or heated home indicates that the air quality control could be improved.
http://www.PlatePals4You.com
Controlling Indoor Humidity
http://www.weather.com/activities/health/allergies/mold/control_humidity.html
Improper Ventilation in your home can increase pollution levels because not enough outdoor air is being brought in to dilute indoor pollutants. Without proper ventilation, those same indoor pollutants are not being carried out of your home.
Typical Sources of Indoor Air Pollutants
http://www.epa.gov/iaq/schools/tfs/guide2.html#Typical%20Sources%20of%20Indoor%20Air%20Pollutants