Developing and Testing Low-Cost Air Cleaners for Safer Spaces during Wildfires

BRETT STINSON, Aurelie Laguerre, Elliott Gall, Portland State University

     Abstract Number: 226
     Working Group: Biomass Combustion: Outdoor/Indoor Transport and Indoor Air Quality

Abstract
Air cleaning can reduce indoor exposure to fine particulate matter (PM_2.5) during wildfire events. However, resource and cost restraints may limit access to air cleaning during such an event, as both commercial devices and high-rated MERV filters that homemade assemblies typically rely upon may be cost-prohibitive and/or in short supply. With these barriers in mind, we sought to develop an air cleaner that utilizes common household fabrics that can be affixed to a box fan. We experimentally determined the clean air delivery rate (CADR) of the prototyped device with five fabrics attached (cotton batting, polyester, felt, flannel, and chiffon), and for comparison, tested two popular, homemade air cleaning configurations with and without flowrate-increasing shrouds, namely a single MERV 13 filter attached to a box fan and the Corsi-Rosenthal box. We employed the pressure-matching method in a 3-meter section of well-sealed ducting, directly measuring the air flowrate at three fan speeds through the device. We then measured the single-pass removal efficiency of the five selected fabric and MERV 13 filters via an apparatus that pulled air through a series of in-line particle counters, challenging filters with two distinct smoke sources: smoldering combustion of a powdered wood product and a smoke proxy from a commercially available smoke detector test aerosol. Preliminary field testing of a full-scale prototype using a simple cotton batting filter show PM_2.5 CADR > 100 cfm is achievable; these field tests results are generally consistent with CADRs calculated from laboratory testing of airflow and removal efficiency.