EPA studies of human exposure to air pollutants indicate that indoor air levels of many pollutants may be 2-5 times, and occasion more than 100 times, higher than outdoor levels. We spend approximately 80% of our lives indoors, half of that in our own homes. The following have been cited causes of or contributing factors to poor indoor air quality:

Inadequate ventilation: Today, our homes and workplaces are sealed tight to maximize energy savings and this results in low circulation of air.

Chemical contaminants from indoor sources: For example, adhesives, carpeting, upholstery, manufactured wood products, copy machines, pesticides, and cleaning agents may emit volatile organic compounds (VOCs), including formaldehyde. Environmental tobacco smoke contributes high levels of VOCs, other toxic compounds, and respirable particulate matter.

Chemical contaminants from outdoor sources: pollutants from cars, plumbing vents and building exhausts

Biological contaminants: Bacteria, molds, pollen, and viruses are types of biological contaminants