Particle Transport and Building Ventilation Limit Indoor Air Cleaner Performance during Wildfire Smoke Events

Portable air cleaners (PACs) are often recommended to mitigate indoor particulate matter levels during wildfire smoke events. These devices can remove smoke particles by using mechanical filters or mechanisms that add energy or chemicals. However, the efficacy of PACs is typically evaluated by manufacturers in confined laboratory settings with pulse inputs rather than multizone buildings with constant sources. Here we use data collected in a test house to investigate how building characteristics, such as the presence of multiple zones, the outdoor air change rate, and air recirculation rate within multiple zones, impact PAC performance when removing indoor particles. Results show that while the tested PAC can remove 90% of pulse-introduced particles within 2 h in a sealed house, simulating a wildfire smoke event with constant infiltration of outdoor PM2.5 yields steady-state cleaning effectiveness of 70%, 45%, and 55% at different locations of the house. We provide evidence-based recommendations for using PACs to reduce the concentrations of infiltrating PM2.5 from outdoor air pollution, such as wildfire smoke or urban smog.