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Up in Smoke: AHU Fires and the Importance of NFPA 90A

Fires never start in air handling units…or do they?

To answer this, look no further than the National Fire Protection Association (NFPA).  Dating back to 1899, the NFPA issued standards dedicated to fire protection in the blowers and exhaust systems of buildings.  This standard is now known as NFPA 90A, which sets forth the “Standard for the Installation of Air Conditioning and Ventilating Systems”, and outlines the stringent compliance requirements for any product or supplementary material exposed to the air stream within an HVAC System.

For over a decade, AQUIS has emphasized the importance of compliance with NFPA 90A where air handling units (AHUs) are concerned.  Why?  Two key reasons:

  • The use of non-compliant coatings and materials inside AHUs is a common but dangerous practice.  Dangerous because air handling units provide ideal environments for intensifying and spreading a fire.  Not only do AHUs provide an endless supply of oxygen to feed a fire, they also provide a pathway via associated ductwork to quickly spread flame and smoke throughout the entire building.
  • NFPA 90A is part of NFPA 101®, Life Safety Code®, which serves as the most widely used consensus code that employs strategies for protecting building occupants from the dangers of fire and smoke.  In conjunction with the Uniform Mechanical Code and International Mechanical Code, these model codes & standards serve as the foundation for all state and local fire codes. 

In short:  NFPA 90A is the law.

<*Continue here from email*>  By definition as the standard is written, there are two key purposes for the existence of NFPA 90A:  1) Restrict the spread of smoke through air duct systems within a building or into a building from the outside; and 2) Restrict the spread of fire through air duct systems from the area of fire origin, whether located within the building or outside.

It’s also worth noting that achieving compliance with this standard is difficult, but ensuring that your air handlers do not contain any non-compliant materials is not.  Leave it to AQUIS, the trusted national leaders in air handler refurbishment.

AQUIS offers the only NFPA 90A-compliant supplementary coating system for use inside air handling units.  With its patented, innovative composite coating system, AQUIS offers a quality customized installed solution for eradicating common and often chronic problems that occur within an air handling unit, and in full compliance with all regulatory requirements, including The Joint Commission.  Learn more about AQUIS compliance with both NFPA 90A and ASHRAE 62.1 here.

NFPA 90A, Section requires “a maximum flame spread index of 25 without evidence of continued progressive combustion, and a maximum smoke developed index of 50 when tested in accordance with ASTM E-84, Standard Test Method for Surface Burning Characteristics of Building Materials”.


To prove NFPA 90A compliance, an installing contractor should provide a valid test report from an accredited laboratory demonstrating that the product or supplementary material in question and intended to be used inside an air handler has been tested per ASTM E-84 and meets the requirements above.  The contractor should also provide verification that the application thickness of the coating, as tested, be no less than the coating application thickness installed in the air handler.

It’s important to also note the distinction between materials with NFPA Class A fire ratings and those that are NFPA 90A compliant.  Although Class A represents the most stringent rating available for building materials, it is not applicable to air handling units where smoke spread is concerned.  Class A materials are required to have a smoke developed index of less than 450, where NFPA 90A compliance requires a smoke developed index of less than 50, being 9 times more stringent than the Class A fire rating.

AQUIS specializes in healthcare, higher education, government, industrial manufacturing and commercial real estate environments, and its long list of notable customers serves as a testament to its longevity and success in the industry.  Some AQUIS customers:

  • Boeing
  • Massachusetts Institute of Technology (MIT)
  • Mayo Clinic
  • Oakridge National Laboratory
  • Boston Children’s Hospital
  • Johns Hopkins University
  • Naval Medical Center Portsmouth
  • NASA – Jet Propulsion Laboratory (JPL)
  • Pfizer

Does your facility have air multiple handling units that could likely benefit from a solution like AQUIS?  If so, please contact us today to see how we can help.

Helpful links and additional resources:

  • Underwriters Laboratories, better known as “UL”, is the global safety science company known for its innovative safety solutions.  UL wrote an informational article called “Products Used in Air Handling Spaces”.  Review this article here.
  • Here you can review some frequently asked questions regarding fire code compliance for coatings installed in air handling units.
  • Sample pages from The Joint Commission/NFPA Life Safety Book for Health Care Organizations can be viewed here.
  • The 2015 Edition of NFPA 101’s Life Safety Code can be accessed online at NFPA’s website.  This link and then create a free access NFPA account in order to view the standard in its entirety.



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