Vac Systems

Air Duct Cleaning: Chemicals used in HVAC systems

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Courtesy of Vac Systems


There is a lot of diversity of information regarding the use of chemicals, cleaners, sealants and coatings inside air handling systems. NADCA recognized the need to provide some direction in this complicated and evolving area and developed the “Chemical Product Application in HVAC Systems” white paper. This article is an overview of NADCA’s white paper and as such, it does not include all of the details of the white paper. It does look at the major topic areas, however. 

It is generally agreed that source removal of contaminants remains the single best method for cleaning and decontaminating HVAC systems. However, chemicals may be applied within HVAC systems for a variety of reasons. This position paper provides an overview of the products and associated techniques utilized in and around HVAC systems.  

It is not necessary to apply chemical products to achieve source removal within an HVAC system. However, applying appropriate cleaning compounds may enhance the cleaning process (e.g., coils, hard surfaces, blowers). 


Workers must be trained to follow procedures on the label and in the current MSDS bulletin for the safe use, handling, and storage of any product used to treat an HVAC system. Appropriate personal protective equipment must be worn, including respiratory protection if required. Correct application procedures must be understood and carried out to avoid hazards from failing to use the product according to the manufacturer’s instructions. 

Types of Antimicrobial Products:

  • Antimicrobial pesticide
  • Sanitizer
  • Disinfectant
  • Fungicide
  • Fungistat
  • Bacteriostat
  • Algaestats 

Note: See the white paper for complete antimicrobial product definitions.  

EPA Requirements:

At this time, the EPA has not accepted any disinfectant, sanitizer or fungicidal products for use in the ductwork of HVAC systems. However, some of these products are accepted for use in other parts of HVAC systems. Those products which have been accepted by the EPA for use in the ductwork of HVAC systems includes ones with the following claims:

  • Fungistatic
  • Bacteriostatic
  • Inhibits odor-causing bacteria and fungi
  • Inhibits stain and damage-causing bacteria, fungi, and algae
  • Deodorizes
  • Inhibits fungi and algae
  • Cleaning (a non pesticidal activity; removal of contaminants)  

Antimicrobial products are available for the treatment of coils, drain pans and other related HVAC system surfaces. Refer to the EPA-accepted product label for specific directions for treatment of these surfaces. 

All antimicrobial pesticides for use in HVAC systems are required to be registered by the EPA. Products without specific HVAC directions are not to be used on these surfaces. A product has only been evaluated based on the directions for use listed on the label. The product is likely not to be effective if used in incorrect amounts or for a different dwell time. 

The label will also include the following information:

  • Specific pest(s) against which the product is effective (meaning that the product has only passed the testing requirements for those organisms listed on the label).
  • Sites (homes, hospitals, etc.) and surfaces (e.g., cooling coil) to which the product may be applied. This means that the product may only be used at those sites and on those surfaces which are identified on the label.
  • Type of equipment or method used to apply the product including application rate and contact time.
  • How often the product is applied. Reapply as directed by the label.
  • In order for the product to be effective it must be used in accordance with the directions for use (application method and rate, and dwell time).
  • Pesticide manufacturers may make available a diluted-solution or secondary-container-use label (which must be consistent with the EPA-approved label) when using concentrated products. 

Typical Use of Antimicrobial Products:

  • The major use of antimicrobial products in HVAC systems is for the inhibition of microbial growth on hard surfaces within components such as air handlers, fans and duct interiors.
  • Disinfectant products may be used in coils, drain pans, and other parts of the air handler.
  • HVAC components that have been exposed to flood water or sewage contamination should be assumed to contain disease-causing organisms and should be disinfected prior to being placed back into service. Since no disinfectants are registered for use in air ducts, systems that have been exposed to contamination from floods, sewage, or similar biological contamination must be evaluated by a qualified individual prior to being placed back into service. Cleaning alone may or may not be satisfactory. Replacement of such duct sections may be necessary.
  • Products chosen must include label directions detailing use in HVAC systems and their components and those directions must be followed. 

Application Method:

Antimicrobial products are generally applied through spraying, wiping or fogging. However, the application method chosen must be one that is in the label directions. Antimicrobials should only be applied after the surfaces have been cleaned. Surface soil or contamination can interfere with the efficacy of a product. When using any antimicrobial product, follow the directions carefully and use the personal protective equipment as directed by the label. 

Best Practices:

  • Follow instructions and safety precautions as per the EPA-accepted label.
  • Use in a well-ventilated area.
  • Keep in original or properly marked container.
  • Label all containers. Where concentrated products are used, label containers holding diluted (ready to use) products.


In addition to exploring antimicrobial products, the white paper also includes sections dealing with the following topics that are not covered in this article:

  • Sealants
  • Resurfacing Materials (repair coatings)
  • Coil Cleaning Compounds
  • Soap & Detergents
  • Degreasers

Using chemicals in addition to source removal is certainly not needed on every air duct cleaning project. But some projects do need the use of chemicals to satisfy project/customer requirements.  Be sure you understand what types of chemicals can be used and what components they can be used on. It is highly recommended that you read and understand NADCA’s Chemical Product Application in HVAC Systems white paper (see link blow).

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