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Air duct cleaning unnecessary for preventing allergies
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March 06, 2000
SAN DIEGO (Reuters Health) -- Air duct cleaning -- promoted as a service to help prevent allergies caused by dust mites and pets -- appears to be unnecessary, because the ducts that deliver conditioned air throughout a house are almost free of the substances that cause allergic reactions.
"Air duct cleaning has been widely promoted as being beneficial, but there were no data we know of," explained Amy Tsay, a research specialist with Indoor Biotechnologies, Charlottesville, Virginia, which specializes in detecting the substances that cause allergies, called allergens.
Speaking at the American Academy of Allergy, Asthma and Immunology annual meeting, Tsay said that of 20 homes surveyed in Virginia, 14 contained detectable levels of dust mite allergens in a bed, sofa, or carpets when checked using the highly sensitive enzyme-linked immunosorbent assay (ELISA) test.
But when the air ducts of these homes were tested, only 2 of the 27 samples showed dust mite allergen at the 0.5 microgram per gram of dust threshold of detection. An allergen level below 1 microgram per gram of dust is considered too low to cause allergic reactions.
Regarding pet allergens, Tsay found that 17 of the 20 homes had cat allergen and 18 had dog allergen. High levels of pet allergens were also detected in the return ("cold air") ducts of these homes. But when she tested the "in" ducts -- the ones that deliver heated or cooled air inside a home -- she found an average reduction of 85% in pet allergens compared with the levels found in the return ductwork.
Most of the homes had standard, inexpensive filters for their forced air heat pump systems, which may be the reason pet allergen levels were significantly reduced, Tsay said. "Ducts are not suitable for mite growth because they are dry and there is a constant air flow," she added.
"Air duct cleaning appears to be of limited value in reducing animal allergen levels in homes, and would not be recommended as a method for controlling mite allergen exposure," the researchers concluded.
Air duct cleaning charges range from $50 to $500 per house, according to Tsay's survey of contractors who advertise on the Internet.