Bathrooms without outside-vented exhaust fans, combustion appliances like kerosene space heaters, drying laundry indoors, and venting clothes dryers to attics or crawl spaces can also increase the humidity levels in your home. Dust mites and their waste products are the most common allergens in indoor air. Dust mites live in rugs and carpets, sheets, mattresses and pillows, and upholstered furniture. Ten to 15 percent of people are allergic to dust mites. First, lower the relative humidity in your home, basement or crawl space, and attic.
Relative humidity is the amount of moisture in the air at a given temperature.
How warm or cool the air is indoors. How much moisture is being vented to the outside. If you can keep relative humidity below 50 percent, you can reduce problems with dust mites, mold, and mildew. A hygrometer can be used to measure indoor humidity levels. You can buy a hygrometer from some nursery or garden stores, and form hardware stores.