When coating large ductwork, a technician needs a respirator. The tech usually uses an airless sprayer, makes sure to protect the bottom of the duct, and sprays as he or she backs out.

If you think the federal tax code is complex, try figuring out what is and what is not allowed when it comes to cleaning ductwork. It is making even the most competent and experienced in the field shake their heads.

“It is an extremely lengthy maze,” said John Bently of Duct Cleaners’ Network.

“It can make your head spin,” admitted Michael J. (MJ) Palazzolo, operations manager for Safety King Inc., Utica, Mich.

Agreed: The subject is complex. Making things more complicated is the fact that regulations are, for the most part, different in each state. What one is allowed to do in Colorado may not be the same in Michigan or California.


First of all, does anything actually need to be applied, sprayed, coated, or fogged into ductwork? Based on NADCA’s ACR 2006 standard (“ACR Standard, 2006 edition: Assessment, Cleaning, and Restoration of HVAC Systems”), it is a judgment call. As the standard states in Section 8.3.1: “Use of antimicrobial treatments and/or coating products may be considered only after mechanical surface cleaning has been performed and the need for such treatment has been deemed necessary.”

Ahh, there’s that magic word: “antimicrobial.” An antimicrobial is designed to prevent, destroy, repel, mitigate, inhibit, or control microbes. However, not just any antimicrobial product can be used in ductwork and HVAC systems. The product has to be approved by the Environmental Protection Agency (EPA). Without its stamp of approval, it is a complete no-no.

Here is where it gets more confusing. EPA puts antimicrobials under the category of pesticides, which must comply with EPA statutes. In EPA’s world, a pesticide is “a product which is intended to prevent, destroy, repel, or mitigate any pest.”

Since we’re talking pesticides here, many states require a license to apply these products. In Michigan, for instance, anyone who performs duct cleaning and uses an EPA-approved antimicrobial product in cleaning is, by law, supposed to have a license to apply the product. One has to submit a certificate of liability insurance, a $100 application fee, and be a certified applicator or have a certified applicator in their business. In order to be a certified applicator, the individual must be 18 years of age or older and must pass a minimum of two exams, one being a general standard exam (CORE) and a minimum of one category or subcategory exam in the applicant’s area of pesticide application.

Palazzolo was totally unaware of such a law until a few years ago when a few people from the local state agriculture office came knocking at Safety King. Palazzolo had to go through the complaint process in order to avoid heavy fines. The business has since met all state laws and continues to get licensed each year accordingly. Palazzolo is concerned that most duct cleaners are not up to code.

“It’s just not being enforced,” he said. “I think they went after the big guy first in order to make a statement.”

At the 2008 NADCA Conference, the association gave Bently exactly 15 minutes to address North American antimicrobial licensing requirements. It was brief simply because each state has, for the most part, a different twist to the issue. “All states are different,” said Bently. “That is the biggest issue.”

Most cart spray systems (as shown here) are used with a commercial airless sprayer. Typical reach is 30 feet in each direction.


In Bently’s estimation, the best solution for a duct cleaner is not to claim one can sanitize or disinfect ducts. Step into that realm and it could get you in trouble, he said. “There are some locations where you can’t apply chemicals into the system,” he said.

To help clarify matters, Bently asked Tracy Lantz, a regulatory specialist in the Antimicrobial Division of the EPA, to provide members of the Duct Cleaners’ Network guidance. Lantz came through with precise definitions in a PowerPoint presentation made at the association’s 2007 conference, held last August in Williamsburg, Pa. They are:

Sanitize:“Is a claim to describe the kill of 99.9 percent of the bacteria on a surface in 5 minutes or less.”

Disinfection:“Is a claim to describe the kill of bacteria with complete kill in 59 out of 60 test carriers in 10 minutes.”

According to Lantz, there are currently only 15 antimicrobial products that have been approved by the EPA for use in HVACR systems. Several of these products have gone through an assessment that meets today’s standards. However, a majority of antimicrobial products have not been through risk assessment for HVACR use. The concerns here are:

• Exposure to applicators and building occupants.

• Labels do not include adequate directions for use on these surfaces.

• Can pesticidal claims for these surfaces be supported by data?

In her presentation, Lantz said EPA’s concerns regarding HVACR products include the fact that “HVACR is a unique use pattern which does require an assessment to determine if exposure could create risk,” it does have reported incidents, and can continue to use products with HVACR directions in accordance with the EPA-accepted label. In other words, the approved products list ducts, air ducts, ductwork, or HVAC on the label and meet EPA approval. As long as the product is used according to the EPA-accepted label, it can legally be used on duct surfaces.

EPA is currently going through the process of approving more products. However, Lantz admits that the agency “does not have an acceptable efficacy method to show that a product can sanitize or disinfect an HVACR system.”

It was also noted that EPA would not develop such a protocol. It said the burden is on the antimicrobial registrant to propose a protocol that supports the pesticidal claim and then submit this protocol to the EPA for review. Once a protocol is approved, “then data may be submitted for review in support of this protocol,” it said.

Echoing Bently’s suggestion, it’s best not to use those magic words in advertising.

“Data has not been provided to show that any of the products registered for HVACR can meet either performance standard,” she said. “Our primary concern is that applicators would not be able to provide adequate coverage of all surfaces within an HVACR system. Thus, claims should not be made to sanitize or disinfect ductwork.”

But what about bleach?

“If using bleach to control a microorganism, use a registered product which lists that organism on the label,” she replied. “There are currently no registered bleach products which include HVACR as a use site.”

Translation: Bleach cannot be used in ductwork or in a system.

Shown is coated insulation with detectors located inside the ductwork. It is recommended that these detectors be either covered or removed before coating.


There are some duct cleaners that use paints and coatings, but is it legal? Lantz had an answer.

“If a pesticidal claim is made, the product itself must be registered or the product must be in compliance with the treated article exemption,” she said, noting that the exemption is “an article or substance treated with, or containing, a pesticide to protect the article or substance itself […paint treated with pesticide to protect the paint coating…] if the pesticide is registered for such use.”

“These are treated article products if claims are limited to protection of the coating,” she added, noting that this may not state that the duct itself is protected.

At the 2008 NADCA Convention, held in San Diego, Peter Haugen, president of Vac Systems International (VSI), Burnsville, Minn., attempted to clear up matters regarding the subject of coating ductwork at a general session (“Coating Applications in HVAC Systems”).

Even though Haugen is certified as an Air Systems Cleaning Specialist and Certified Ventilation System Inspector by NADCA and has over 25 years’ experience in the industry, there are still some “iffy” calls, in his estimation. Overall, though, he believes coatings enhance or extend the life of HVAC systems, “giving the building owner a less expensive option to replacing ductwork and other HVAC components.”

At the same time, coatings give the contractor “another service and/or solution to offer customers, providing existing conditions qualify to clean and coat,” he said.

According to Haugen, typical components that can be coated include ductwork, air handlers, rooftop units, heat pumps, variable-air-volume (VAV) boxes, and insulated diffusers. However, some of the questions contractors need to ask are:

• Is the product suitable for the insulation or hard surface on the project?

• What is the coverage rate?

• What is the drying time?

• How strong is the odor?

• What is the viscosity of the product and how easy or hard is it to apply?

• What is the total cost?

One needs to clean ductwork before coating. If the insulation is in good enough condition to clean, it is most likely in good enough condition to coat.

In his estimation, coatings can lock down remaining loose fibers, isolate residual spores left in insulation, provide more durable surface “that is more resistant to air erosion, moisture, and dirt accumulation.” Plus, after a coating is in place, it makes the system easier to clean in the future, he said, plus enhances and extends the life of that surface.

The tricky part is coating duct liner or fiberglass duct board. His No. 1 rule is: If you can’t clean the insulation, you can’t apply a coating to the insulation. “You must first clean the insulation,” he said. “If the insulation is in good enough condition to clean, it is most likely in good enough condition to coat.”

Possible application tools include paintbrush, paint roller, commercial airless sprayer, cart spray system, and even robotic spray systems. Regarding the airless sprayers, he cautioned that they must be sized to handle the coating one wants to apply, as different coatings can require a different size airless sprayer. “Check with the coating manufacturer for requirements,” he suggested.

Know also, he said, that many airless sprayers have limited reach, and the equipment can cost anywhere from $1,000 to $2,500.

Robotic spray systems, on the other hand, are mostly used with a commercial airless sprayer. They have a typical reach between 80 feet and 100 feet, are included with a set of spray nozzles, have various height adjustments, and can cost anywhere between $5,500 to $15,000.

Haugen noted that common sense should be the guide when coating, be it large ductwork; large walk-in air handlers; small to medium air handlers; small to medium ductwork; and/or small to medium ductwork without a cart or robotic system. How does one know how much coating is enough?

“There is no one answer because the existing condition of the insulation on each project is different,” said Haugen. “Do a test section if possible.”

In the latter case, the customer and the contractor should agree as to what is adequate coverage as “this eliminates potential disputes,” he said. This test section will also help the applicator determine spraying speed and coverage needed.

What is allowed and what is not allowed in regard to coating products? If the manufacturer of the product intends to make a pesticidal claim, Lantz said EPA registration of these products is considered on a case-by-case basis “dependent on active ingredients, directions for use, and claims.”

Sidebar: Pesticide Web Pages

John Bently of Duct Cleaners’ Network provided the following Websites that address the pesticide issue for each state in the United States:









District of Columbia:http://doh.dc.gov/doh/cwp/view,A,1374,Q,585707,dohNav_GlD,1814.asp

Florida:http://www.flaes org/aes-ent/index.html


















New England:http://www.ianrpubs.unl.edu/epublic/live/g479/build/g479.pdf


New Hampshire:http://www.nh.gov/agric/divisions/pesticide_control/index.htm

New Jersey:http://www.nj.gov/dep/enforcement/pcp/bpo-appcom.htm

New Mexico:http://nmdaweb.nmsu.edu/pesticides/applicators/Pesticide%20Applicator%20Licensing%20Guide.html

New York:http://www.dec.ny.gov/chemica1/298.html

North Carolina:http://ww.agr.state.nc.us/SPCAP/pesticides/index.htm

North Dakota:http://www.agdepartment.com/Programs/Plant/Pesticides.html





Rhode Island:http://www.dem.ri.gov/programs/bnatres/agricult/

South Carolina:http://entweb.clemson.edu/pesticid/regulat.htm#PesticideRegulations

South Dakota:http://www.state.sd.us/doa/das/hp-pest.htm







West Virginia:http://ww.wvu.edu/~agexten/ipm/pestprog/educate/licenreq.htm




Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA):http://www.lipca.com/state_regulations.php; http://pestworld.stjohn.hawaii.edu/pat/links.html

Helpful map:http://agri.nv.gov/AGRI_USMap.htm

Sidebar: Products Registered for HVAC Use

Publication date:07/07/2008