AB-10-013 -- Cleaning Initiation Criteria for Heating, Ventilation and Air-Conditioning (HVAC) Systems in Non-Industrial Buildings PDF

In the United States and Canada, the initiation of air system cleaning is based on visual inspection, which is subjective and impractical for major cleaning work. The association for the prevention and study of contamination (ASPEC) in France has published a guide on objective sampling methods (numerical evaluation method) for keeping non-porous air systems clean. However, the sampling methods have some deficiencies. The objectives of this study were to reproduce in the laboratory different levels of cleanliness in non-porous ducts of HVAC systems, to compare a new method for sampling surface dust in ducts with those methods cited in the literature, and to compare the numerical evaluation method (objective method) to the visual method (subjective one). For each of the simulated cleanliness conditions, a committee of specialists did a visual assessment based on a scale of 3, where level 1 meant normal, 2 meant above normal, and 3 meant serious. According to these assessments, the established initiation criteria correspond to 0.2 grams per square meter (0.00066 ounces per square foot) for the NADCA method, 0.3 g/m² (0.00098 oz/ft²) for the ASPEC method, and 0.6 g/m² (0.002 oz/ft²) for the new method. These criteria are significantly different (p=0.05) from one another. When replacing the visual method, any of the surface sampling methods can be used, insofar as the corresponding initiation criterion is applied, but these results need to be evaluated in real ducts with real dust before being used as cleaning initiation criteria.