Validation of the Criteria for Initiating the Cleaning of Heating, Ventilation, and Air-Conditioning (HVAC) Ductwork Under Real Conditions

Abstract

Dust accumulation in the components of heating, ventilation, and air-conditioning (HVAC) systems is a potential source of contaminants. To date, very little information is available on recognized methods for assessing dust buildup in these systems. The few existing methods are either objective in nature, involving numerical values, or subjective in nature, based on experts’ judgments. An earlier project aimed at assessing different methods of sampling dust in ducts was carried out in the laboratories of the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST). This laboratory study showed that all the sampling methods were practicable, provided that a specific surface-dust cleaning initiation criterion was used for each method. However, these conclusions were reached on the basis of ideal conditions in a laboratory using a reference dust. The objective of this present study was to validate these laboratory results in the field. To this end, the laboratory sampling templates were replicated in real ducts and the three sampling methods (the IRSST method, the method of the U.S. organization National Air Duct Cleaner Association [NADCA] and that of the French organization Association pour la Prévention et l’Étude de la Contamination [ASPEC]) were used simultaneously in a statistically representative number of systems. The air return and supply ducts were also compared. Cleaning initiation criteria under real conditions were found to be 6.0 mg/100 cm² using the IRSST method, 2.0 mg/100 cm² using the NADCA method, and 23 mg/100 cm² using the ASPEC method. In the laboratory study, the criteria using the same methods were 6.0 for the IRSST method, 2.0 for the NADCA method, and 3.0 for the ASPEC method. The laboratory criteria for the IRSST and NADCA methods were therefore validated in the field. The ASPEC criterion was the only one to change. The ASPEC method therefore allows for the most accurate evaluation of dust accumulation in HVAC ductwork. We therefore recommend using the latter method to objectively assess dust accumulation levels in HVAC ductwork.

Keywords:

• cleaning
• criteria
• HVAC ductwork
• real conditions
• validation

ACKNOWLEDGMENTS

The authors wish to thank the nonindustrial establishments that gave access to their systems and the HVAC cleaning companies that facilitated entry into these systems, as well as Laurent Gratton of the IRSST and the members of the follow-up committee. Special thanks go to the experts/evaluators: Ali Bahloul, Simon Aubin, Louis Lazure, and Nicole Goyer, and technicians Zélie Fortin and Claude Létourneau, all of the IRSST. Sincere thanks also go to Sylvie Bédard of the Association paritaire pour la santé et la sécurité du travail (Joint Sector-Based Occupational Health and Safety Association) in the social services sector for having opened many doors for us.