Air ducts help move heat, cooling and air from room to room within a building. In the process, they become home to a variety of contaminants, including some potentially hazardous to health. Cleaning removes trapped dirt and pollutants, but if it's done improperly, it can release them back into the air. Negative pressure systems keep pollutants and dust stirred up in the cleaning process from becoming airborne. Negative pressure duct cleaning uses negative suction and pressure to pull pollutants and dirt from air ducts and into a collection receptacle.
Negative pressure systems prevent airborne contamination during the cleaning process. During cleaning, dirt and other pollutants can leak out of holes and gaps in the air duct system. These pollutants include mold spores, fungi, fiberglass and various other allergens. Negative pressure systems suck contaminants in so the risk of pollutant leakage is extremely low. An expert quoted in Air Conditioning Heating & Refrigeration News argues negative pressure is important "for the health and safety of workers and occupants" in buildings where ducts are being cleaned (See Reference 1).
Cutting access holes for cleaning creates new points of escape for pollutants. Negative pressure machines can be connected to hoses and nozzles with a range of 100 feet. This long range minimizes the number of access points needed (See Reference 1).
Negative air pressure systems come with a hefty price tag. Additionally, training employees to use the systems can be very costly. For this reason, many air duct cleaning companies elect to use less safe methods of duct cleaning (See Reference 1).
Disagreement exists over the benefits of air duct cleaning. Dirt and pollutants stick to the surfaces of the air ducts instead of floating around loosely. The Environmental Protection Agency says there is no "conclusive" evidence dirty air ducts impact health or that the allergens and dirt in the ducts enter the "living space." There are certain conditions under which the EPA recommends cleaning, including the presence of mold, rodents and insects (See Reference 2).
The stickiness of the pollutants serve as a selling point for negative pressure duct cleaning. These particles do not pose a danger until they are loosened by the cleaning process. Once loose, the particles become airborne. Negative pressure systems help prevent risks by sucking the particles up and depositing them into a container while they are still inside the air duct.
If you are considering have your air ducts cleaned, the EPA recommends thoroughly checking the credentials and references of any contractor before hiring. The agency also warns consumers to stay clear of companies that promise numerous, unproven health benefits (See Reference 2).
- Air Conditioning Heating & Refrigeration News; How-to: Experts tout 'negative air' to clean ducts, purge contaminants; Heidi Nye; July 15, 1996.
- EPA: Should You Have the Air Ducts in Your Home Cleaned?
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