Charles Buell has provided information that I've been meaning to look up for my clients. Thank you, Charles, for saving me some time! And hopefully, for saving my clients some money.
Now that another heating season is here, it seems the airwaves of both Radio and TV are filled with companies selling their duct cleaning services.
As counter-intuitive as it might seem, most duct cleaning is not only unnecessary but can make indoor air quality worse.
There are a few reasons when duct cleaning might be advised, but most of these are caused by circumstances that do not amount to everyday use of the duct system. For example Ductwork that has been flooded, contaminated with toxic materials, infested with rodents, or coated with nicotine from smoking, might benefit from cleaning. In these instances however I would recommend replacement—not cleaning.
Ductwork that has not been properly protected during remodeling or new construction might benefit from cleaning as well.
Generally speaking with normal use of the system, and proper installation and maintenance of the filtration system, duct cleaning should not be “routine” and is typically an unnecessary expense. Cleaning ducts can remove the larger debris, leaving the smaller debris to be blown around in the ductwork and back into the living environment. There are ways to clean the ducts without this happening but it is not cheap. Certainly not the $199.99 advertized on TV.
Here is what the EPA has to say about duct cleaning:
Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts. This is because much of the dirt in air ducts adheres to duct surfaces and does not necessarily enter the living space. It is important to keep in mind that dirty air ducts are only one of many possible sources of particles that are present in homes. Pollutants that enter the home both from outdoors and indoor activities such as cooking, cleaning, smoking, or just moving around can cause greater exposure to contaminants than dirty air ducts. Moreover, there is no evidence that a light amount of household dust or other particulate matter in air ducts poses any risk to your health. (The American Lung Association concurs with this assessment as well.)
Dust in the ductwork actually acts as a filter to assist in cleaning the air.
One reason to clean the ducts, which is almost never discussed, is to improve air flow and thus system efficiency. This is not discussed because it would take EXTREME amounts of dust in the ductwork to affect efficiency greatly. Given the benefits of some amount of dust in the ductwork, one could argue that any perceived loss of efficiency is offset by the Indoor Air Quality benefits.
One can also argue that brand-spanking-new-clean ducts allows for more particulate to be in the air because the ductwork is not filtering it out.
It is imperative that when, and if, you have your ducts cleaned, that it be verified that the service provider will take the necessary steps to protect the inhabitants from exposure to dislodged particulate as well as to the chemicals used in the cleaning process.
If HEPA filtration was not used, if respirators were not used, if all supply and return registers were not removed or if you were allowed to remain in the home during the process, you might very well ask what you have really spent your money on and what will be the affect on your home’s indoor air quality—and you.
For more information see “Duct Cleaning for Quackers”
Charles Buell, Real Estate Inspections in Seattle
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PS, for those of you that are new to my blog (or for some other "unexplained" reason have never noticed)all pictures and smiley-face inserts (emoticons) (when I use them) have messages that show up when you point at them with your cursor.
WA State, Home Inspector Advisory Licensing Board