UC Berkeley

Fine particulate matter (PM2.5) contributes to millions of excess deaths worldwide each year. Wildfires are a major source of PM2.5 and sheltering indoors using central air filtration is effective in reducing indoor PM2.5 levels during an event. We analyzed smart thermostat usage in California homes during the 2020 wildfire season and found that central air is not generally utilized for air filtration. We evaluated the effectiveness of operating central air systems to reduce indoor PM2.5 levels using a mass balance model. Simulation results showed up to a 56% reduction in indoor PM2.5 during wildfire days from central air filtration. Installing a MERV 13 filter, as opposed to a MERV 10 filter, can further lower indoor PM2.5 concentrations by up to 31%. Using central air systems for filtration can match the efficiency of four portable air cleaners in an average Californian home. These results may serve as the basis for an automated control logic to utilize central air filtration during a wildfire event.