Particle and Gas-Phase Evaluation of Air Cleaners Under Indoor Wildfire Smoke Conditions

Abstract

There exists limited testing of air cleaners under indoor wildfire smoke conditions. This study characterized 13 air cleaners, determining size-resolved particulate matter (PM), black and brown carbon, and volatile organic compound (VOC) clean air delivery rates (CADRs). Two do-it-yourself (DIY) configurations composed of MERV 13 filters affixed to a box fan proved effective at removing particles in the 1−2.5 μm diameter range with average CADRs of 1467 and 842 m 3 /h, respectively. In contrast with units with HEPA filters, PM CADRs decreased with decreasing particle size for DIY builds. Among air cleaners designed to remove gas-phase pollutants via sorbents, two devices produced benzene CADRs >190 m 3 /h. Air cleaners that add reactive species to the air yielded mixed results and warrant further analysis. A wildfire event was modeled with experimentally determined PM 2.5 and benzene CADRs for four devices that spanned the range of experimental CADRs; results suggest appropriately sized air cleaners reduce exposure to indoor wildfire smoke both during and after the event. Modeling of indoor spaces during and after smoke events demonstrates the need for thoughtful public messaging around the implementation of air cleaners, as CADRs vary considerably depending on the pollutant being targeted and the mechanism by which it is removed.