Independent laboratory testing identifies structural failures in flexible ductwork exposed to negative-air cleaning forces, prompting calls for updated industry standards.

Bend, Oregon — A newly published, peer-reviewed study in the Spring 2026 issue of The Journal of Cleaning Science found that negative-air duct cleaning may cause structural damage to flexible HVAC duct systems. Authored by applied-physics practitioner and biosecurity specialist David Hart, the research combines engineering analysis, field observations, and independent laboratory testing conducted by Element Materials Technology. The study was published by the Cleaning Industry Research Institute International (CIRI) and peer reviewed by industry experts including Dr. Keri Lestage, PhD, PMP, CIC, and Dr. Brandon White.

Flexible duct systems are widely used throughout residential and commercial buildings due to their affordability and ease of installation. According to the study, these systems are designed for positive airflow pressure and may experience structural failures when exposed to vacuum pressures commonly generated during negative-air duct cleaning procedures.

Independent testing subjected flexible duct samples to conditions representative of real-world cleaning operations, including negative pressure alone and negative pressure combined with mechanical agitation. While control samples showed no damage, multiple test samples developed adhesive seam failures, liner perforations, holes, and delamination.

“The mechanical evidence, field observations, and practical constraints suggest that negative-air cleaning may be incompatible with many flexible HVAC duct systems,” Hart writes in the study. “These findings warrant a reevaluation of current cleaning practices and industry standards as they relate to flexible ductwork.”

The research identified adhesive seam degradation and delamination as primary failure mechanisms. According to the study, many of these failures occur internally and may not be visible during routine inspections.

Researchers also note that damaged ductwork may create pathways for moisture intrusion, condensation, and contamination. Over time, these conditions may contribute to mold growth, reduced HVAC efficiency, and other indoor air quality concerns.

“Having developed the seam-seal adhesives used in flexible HVAC ducting, I’ve seen firsthand that while these adhesives are engineered for significant positive pressure, even modest negative pressure can compromise their integrity,” said John Miles, President and Chief Science Officer at Superstratum, as quoted in the study.

Dr. Keri Lestage, a peer reviewer of the study and founder of CleanOps Collective, believes the findings challenge long-standing assumptions within the HVAC cleaning industry.

“Negative-air cleaning has been the standard method for decades,” said Lestage. “But this paper makes a compelling case that ‘we’ve always done it this way’ isn’t good enough anymore. The science has moved, and industry practices should evolve with it.”

Because flexible ductwork has been installed in millions of residential and commercial buildings over the past several decades, the study raises broader questions about whether current industry standards adequately account for the structural limitations of modern flexible duct systems.

The study concludes that cleaning methods operating within the design limitations of flexible duct systems may provide a mechanically compatible alternative to traditional negative-air cleaning approaches and recommends that industry standards be reviewed and updated accordingly.

The full study, Structural Incompatibility of Negative-Air Cleaning in Flexible HVAC Duct Systems, appears in Volume 7, Issue 1 (Spring 2026) of The Journal of Cleaning Science.

About David Hart

David Hart is a U.S. Army veteran and Certified Forensic Operator with extensive experience in HVAC cleaning and decontamination across residential, commercial, and high-risk environments, including crime scenes, illicit drug contamination, and bioterrorism-related incidents. He is the author of the HVAC Standards for Forensic Restoration and serves as a Scientific Advisor and Board Member of the Biosecurity Emergency Response Team–Scientific Operators Group (BERT-SOG). Hart also serves as the HVAC cleaning and decontamination instructor for the world’s leading forensic restoration organization and has presented at international conferences, including delivering the opening keynote address at a major industry summit in Australia.

Hart holds multiple U.S. patents for HVAC cleaning and decontamination technologies and has authored several peer-reviewed research papers examining HVAC cleaning pressures and decontamination methodologies. His research has become a widely cited reference within the field and focuses on developing evidence-based protocols for HVAC decontamination in complex and high-risk environments.