Chemical biocides are regulated by EPA under Federal pesticide law. A product must be registered by EPA for a specific use before it can be legally used for that purpose. The specific use(s) must appear on the pesticide (e.g., biocide) label, along with other important information. It is a violation of federal law to use a pesticide product in any manner inconsistent with the label directions.
The EPA and CMHC researchers used different methodologies. The CMHC study called on several duct-cleaning services. The companies were not made aware they were part of a study, and the researchers did not control for time spent or methods used. The EPA study prescribed and controlled methods used on a smaller number of homes. While the duct-cleaning industry argues both studies have flaws, no other research has challenged the findings. And although the equipment and methods used by duct-cleaning companies have changed since these studies were conducted, the air ducts in homes haven’t.
Duct cleaning is a complete scam, I was a “duct cleaning technician” for a whole week before I was fired for not upselling elderly widowed women $2000 extra for “toxic mold remediation” when their ducts were spotless to begin with. The last two days I was employed there I worked as a “helper” alongside a technician thats been with the company 7 years. He scammed every customer on mold and would at times get as much as $2500 extra for treating “toxic mold” in a typical 3 bedroom house in the suburbs. Wait…it gets even better, the “Biocide” the company used was simply a cheap $4.99 per gallon bought at Home Depot air freshener with no anti-microbial properties that was fogged into the HVAC system for 5 minutes, maybe using 1/2 cup of the stuff. In order to provide the customer with evidence of “mold infestation” the technician would be given bogus mold tests that always resulted in “toxic spores present” regardless if you swabbed the actual duct or nothing at all. Not to mention the actual duct cleaning job (typically $400) did basically nothing and the homeowner could’ve done a better job with a shopvac
“Ideally, the inside surface will be shiny and bright after cleaning. Duct cleaning may be justifiable to you personally for that very reason: you may not want to have your house air circulated through a duct passage that is not as clean as the rest of the house. However, duct cleaning will not usually change the quality of the air you breathe, nor will it significantly affect airflows or heating costs.”
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.