Whole House Particle Removal and Clean Air Delivery Rates for In-Duct and Portable Ventilation Systems

Abstract

A novel method for determining whole house particle removal and clean air delivery rates attributable to central and portable ventilation/air cleaning systems is described. The method is used to characterize total and air-cleaner-specific particle removal rates during operation of four in-duct air cleaners and two portable air-cleaning devices in a fully instrumented test home. Operation of in-duct and portable air cleaners typically increased particle removal rates over the baseline rates determined in the absence of operating a central fan or an indoor air cleaner. Removal rates of 0.3- to 0.5-microm particles ranged from 1.5 hr(-1) during operation of an in-duct, 5-in. pleated media filter to 7.2 hr(-1) for an in-duct electrostatic air cleaner in comparison to a baseline rate of 0 hr(-1) when the air handler was operating without a filter. Removal rates for total particulate matter less than 2.5 microm in aerodynamic diameter (PM2.5) mass concentrations were 0.5 hr(-1) under baseline conditions, 0.5 hr(-1) during operation of three portable ionic air cleaners, 1 hr(-1) for an in-duct 1-in. media filter, 2.4 hr(-1) for a single high-efficiency particle arrestance (HEPA) portable air cleaner, 4.6 hr(-1) for an in-duct 5-in. media filter, 4.7 hr(-1) during operation of five portable HEPA filters, 6.1 hr(-1) for a conventional in-duct electronic air cleaner, and 7.5 hr(-1) for a high efficiency in-duct electrostatic air cleaner. Corresponding whole house clean air delivery rates for PM2.5 attributable to the air cleaner independent of losses within the central ventilation system ranged from 2 m3/min for the conventional media filter to 32 m3/min for the high efficiency in-duct electrostatic device. Except for the portable ionic air cleaner, the devices considered here increased particle removal indoors over baseline deposition rates.

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

“…Although this method is valid, it is time consuming and they estimated the experimental uncertainty to be approximately 20% or more. MacIntosh et al (2008) simply assumed that airflow rates remained constant with each filter, an unlikely assumption for the range of filters tested and the types of systems in most residential and light-commercial systems (Stephens et al 2010a(Stephens et al , 2010b. The flow plate device that we used has been shown to be more accurate than previous methods and is relatively quick to use (Francisco and Palmiter 2003).…”

“…The whole-house test methods in Offermann et al (1992), Howard-Reed et al (2003), Wallace et al (2004), and MacIntosh et al (2008) were refined for the purposes of this work. The method consists of the same general practices: artificially elevating indoor particle concentrations and measuring the subsequent concentration decay with and without a filter installed in the operating HVAC system, while simultaneously measuring the AER through the building by tracer gas decay.…”

“…Finally, whole-house test methods are generally time intensive. Single test durations were 4-5 h in Offermann et al (1992) and were reduced to approximately 2 h in MacIntosh et al (2008), whereas upstream and downstream particle concentrations can be measured in minutes.…”

“…The in situ performance of filters and other HVAC components that may remove particles has been field tested using two primary methods: (1) by measuring concentrations upstream and downstream of the filter or component in question (Burroughs and Kinzer 1998;Fugler et al 2000;Jamriska et al 2000;ASHRAE 2008), and (2) by measuring the difference in overall particle loss rates in an indoor environment with and without a filter installed (Offermann et al 1992;Howard-Reed et al 2003;Wallace et al 2004;MacIntosh et al 2008).…”

The benefits of whole-house in-duct air cleaning in reducing exposures to fine particulate matter of outdoor origin: A modeling analysis

“…The efficiency, removal rates, and other performance characteristics of some of these devices have been characterized empirically (Chen et al, 2006;Shaughnessy and Sextro, 2006;MacIntosh et al, 2008). The potential for advanced filtration technology to mitigate indoor exposure to PM 2.5 of ambient origin in Europe was estimated from results of the EXPOLIS study (Hanninen et al, 2005).…”