Effects of Negative Air Duct Cleaning on Flex Ducts: NADCA's Response

By now you've likely come across the white paper, Effects of Negative Air Duct Cleaning on Flex Ducts, which was released this past December. For many, this has triggered frustration and confusion as to whether or not NADCA supports the claims within the document, and rightfully so. NADCA was in no way involved with the development or review of this paper and does not support the statement that negative air cannot and should not be used to clean flex duct because of the damage it can cause. It is NADCA’s position that this statement is simply untrue.

NADCA takes the stance that a system with flex ductwork, like all systems, should be assessed and evaluated to determine the cleaning protocol and scope of work. According to ACR, The NADCA Standard, section 1.10, System Components Assessment:

Information collected from the HVAC inspection shall be documented and evaluated to assess the condition of the HVAC system components at the time of the inspection.
The assessment shall include a recommendation on the need for cleaning, a clearly defined scope of work for the cleaning and restoration project, recommended cleaning techniques, a determination of the environmental engineering controls required for the workspace, and any unique requirements.

Therefore, only during the assessment, can the technician determine if cleaning is the best course of action or if replacement is necessary. Simply stating — as the white paper does — that the use of negative air machines for cleaning this type of ductwork isn’t an option is creating the false notion that cleaning flex ductwork in accordance with ACR, The NADCA Standard (which is centered around using negative pressure), is not possible, which is not the case.

Several NADCA members have spoken out about the contents of the white paper, insisting that the process of duct cleaning is rarely the culprit when it comes to damaged flex ductwork and in this case, the negative air machines are being blamed. However, it is more than likely that the negative air being used during the cleaning is not more than what the flex duct was designed to handle. While there are older versions of the material that may not be able to withstand the process and need to be replaced due to already existing damage, but most flex ducts are made with a metal spiral support to allow for contact vacuuming and other cleaning methods.

In response to the white paper, NADCA has convened with several subject matter experts to submit a clear refutation to the published document. Their statements are available below.


Clint Orr, ASCS, CVI
NADCA Second Vice President, Board of Directors
Education & Membership Committee Chairperson
Regina, SK, Canada

"I have been in the HVAC industry for over 20 years. Along the way I have installed, replaced, and cleaned thousands of feet of flex duct. The 2021 edition of ACR, the NADCA Standard, provides the “how to” and guidelines on best practices for the assessment, cleaning and restoration processes related to HVAC systems and their components..." CLICK HERE to continue reading


Tyler Batchelder, ASCS,CVI
NADCA Board of Directors
Colchester, VT

"In response to the White Paper Effects of Negative Air Duct Cleaning on Flex Ducting, I would make the argument that the duct cleaning process helps identify areas where flex duct has otherwise been damaged or disconnected more so than creating the situation. CLICK HERE to continue reading


Zachary Ortwine, ASCS, CVI
NADCA Member and Volunteer
Richmond, VA

"The premise of the white paper Effects of Negative Air Duct Cleaning on Flex Ducting appears to be that because the negative air equipment manufacturers designed their equipment to exceed manufacturers maximum-rated negative pressure of flexible ducts that the use of this equipment will result in damaging the flex ducts. However, in my years of field-based experience in residential and commercial projects which involves cleaning flex ducts I have never damaged a flex duct due to negative pressure created by our gasoline-powered negative air machines." CLICK HERE to continue reading