Studies show that the Indoor Air Quality (IAQ) in the average home can be up to 100 times more polluted than outdoor air. Modern, almost airtight buildings with low fresh air exchange do not provide sufficient ventilation to remove indoor air contaminants. Boosting ventilation would improve the indoor air quality but would be very costly due to the energy losses in heated or air-conditioned air.
Americans spend on average 93 percent of their time indoors, which makes indoor air quality critical to their health. Indoor air pollution is even more critical in their homes, where they spend most of their time - on average 70 percent (more for children).
The Environmental Protection Agency warns that indoor air pollution is one of the five most urgent environmental risks to public health.
One of the major problems are biological contaminants like molds, mildew, and dust mites, which prosper in the warm and humid indoor air.
The most common indoor biological contaminants are molds, mildew, bacteria, viruses, house dust mites, animal dander or saliva, and pollen. These particles are too small to be visible or to settle by gravity, and travel perpetually suspended in air.
The essential pre-condition for biological growth is moisture. Suitable conditions can be found in bathrooms, damp or leaking basements, humidifiers, air conditioners, carpets and upholstered furniture.
Reducing moisture lowers the biological contaminants in indoor air - the ideal relative humidity is 30 to 50 percent.
"Dust mites, molds, animal dander, and other biologicals are found in some degree in every home and workplace. High relative humidity is the primary factor encouraging biological agents to grow and be released into the air." (US EPA)
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Indoor biological pollutants are a major contributing factor to asthma and allergies, which have become a growing public health problem, particularly among children.
EPA warns: "Biological agents are known to cause three types of human diseases:
Many health effects are associated with biological contaminants:
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In the outdoor air, microbes usually die off due to sunlight, temperature extremes, dehydration, and ozone, although spores and some environmental bacteria are naturally more resistant. But the moist and controlled indoor climate favors the survival and transmission of contagious human pathogens, as well as some outdoor fungi and bacteria.
Airborne particles and large molecules that contain living organisms or were released from living organisms are called bioaerosols. The size of bioaerosol particles varies from 100 microns (thousandths of a millimeter) to 0.01 micron:
The diameter of human hair is 75 to 100 microns. Particles smaller than 0.5 microns do not settle by gravity but remain perpetually suspended in the indoor air we breathe.
Airborne Respiratory Pathogens - Aerobiological Engineering.
Dust mites have been identified as the single most powerful trigger for asthma attacks. Mites thrive on dead human skin cells in bedding, carpeting and upholstery. These microscopic animals multiply by the thousands in warm and humid conditions, when humidity exceeds 45 percent and temperature is above 65° F.
Dust mites leave behind droppings and disintegrating body parts that we inhale. Each dust mite produces about 20 pellets which are invisible to the human eye (10 to 24 microns in size). It is the protein in the fecal products and disintegrating body parts of dust mites that is one of the most powerful biological allergens. Over 10 percent of people are allergic to dust mite extracts.
Mites have eight tiny legs with sticky pads, which enable them to burrow deep into carpet fibers, mattresses or furniture and easily resist the pull of even the most powerful vacuum cleaners. The average bed can easily have over 10,000 dust mites living in it. One-tenth of the weight of an old pillow can be sometimes attributed to dust mites and their droppings! Because of dust mites, the average mattress will double its weight in 10 years!
Dust mites do not drink water but absorb moisture from the air. They cannot survive in humidity below 45%. Your main weapon against dust mites, just as against molds, is reducing humidity in your house. And since most moisture gets into your house in the form of invisible water vapor from the basement, seal your basement with RadonSeal and caulk all cracks or openings. Install bathroom and kitchen exhaust fans.
For prevention, install an open jar of BioZap Air Purifier under the bed. It releases vapors of essential oils, which are deadly to mites and biological contaminants. Or if there already is an infestation, spray the bed, carpeting and upholstery with BioZap Mold & Mildew Cleaner.
Reduce the humidity in your home and minimize the biological pollutants in the indoor air.