Comparison of Test Methods for Determining the Particle Removal Efficiency of Filters in Residential and Light-Commercial Central HVAC Systems

Central heating, ventilating, and air-conditioning (HVAC) filters are often the dominant mechanism for particle removal in buildings. However, little is known about filter performance in real environments, particularly in residential and light-commercial buildings where particle concentrations and compositions can be very different from laboratory test conditions. This article explores differences in HVAC filter test protocols and refines a whole-house method for in situ testing of filters for size-resolved particle removal efficiencies. Results from the in situ method are compared with those from a simple upstream-downstream method for three types of commercially available filters in an unoccupied test house. Results from both field methods are compared with standardized laboratory test results as measured by an independent laboratory and as reported by the manufacturer. In general, comparisons between filter efficiency as measured by the refined whole-house method and as measured by the upstream-downstream method resulted in similar values of particle removal efficiency for many particle sizes and compared well with standardized lab tests, although experimental uncertainties were generally greatest for the whole-house method. However, the refined whole-house method has the added benefit of allowing an investigation of more particle interactions in an indoor environment, including deposition to ductwork and other HVAC system components, exfiltration through duct leakage, and bypass airflow around filters. Both field methods can be used to investigate the effects of HVAC system characteristics and dust loading on filter efficiency in real environments.