In-situ Assessment of Particle Air Cleaning

Rafsan Nahian, JEFFREY SIEGEL, University of Toronto

     Abstract Number: 123
     Working Group: Indoor Aerosols

Abstract
Air cleaner performance is context specific, and the same air cleaner will perform differently in different environments owing to differences in background loss rates (eg, deposition and ventilation), room mixing, and indoor and outdoor sources. Further the same air cleaner will perform differently over time for a given environment because of variations of these factors as well as air cleaner performance degradation. The goal of this research was to design and utilize an in-situ test to allow for in-situ testing of any particle air cleaner using low-cost instrumentation. The test switches between the operation of the air cleaner and a co-located sham air cleaner (a white noise generator that operates by moving air and creates the same sound pressure level as the air cleaner). The effectiveness can be explicitly calculated from the concentrations during placebo and air cleaner operation periods and the air cleaner loss rate can be calculated by the difference in the rates of decay of the pollutant of interest between the two periods. Here, we report on pilot tests in a residence to determine the appropriate duration of each air cleaner/placebo period, the overall duration of the test, the impact of different data analysis approaches (eg, truncating data from the beginning of each air cleaner/placebo period). The results suggest that a duration of each operation period of 2 hours 30 minutes, excluding the data from the first 30 minutes of each period, and an overall experimental duration of approximately 48 hours yielded robust results when compared to results collected over a week. Results were expanded to five different air cleaners and five different environments. The collective results show that the test is very sensitive and can detect air clean air delivery rates as low as 50 m3/h. The testing shows wide variability in the effectiveness of an air cleaner in a given environment over short time scales (largely owing to variations in ventilation as well as source patterns) and highlights the importance of in-situ measurements to characterize these variations.