Characterizing outdoor infiltration and indoor contribution of PM2.5 with citizen-based low-cost monitoring data

Exposures and behavioral responses to wildfire smoke

“…This is consistent with a recent study on Purple Air monitor PM 2.5 calibration that found PM 2.5 concentrations derived from Purple Air particle counts best explained EPA measured PM 2.5 anomalies both overall and specifically during wildfire events (59). In light of these findings, we follow several recent publications (38,40,59) and present our main infiltration results with PM 2.5 concentrations derived from Purple Air particle counts. However, we also present infiltration estimates for all three versions of PM 2.5 concentrations (in each case using the same measure for indoor and outdoor concentrations) and find estimates are highly correlated across choice of measure (Fig S7).…”

“…Measuring indoor and outdoor household PM 2.5 using Purple Air To estimate household infiltration of outdoor PM 2.5 into indoor environments, we utilize data collected by low-cost Purple Air monitors measuring indoor and outdoor PM 2.5 concentrations. Raw 10-minute observations were downloaded for all available indoor and outdoor Purple Air monitors in the contiguous United States and then cleaned according to the procedures developed by recent studies (38,40) in order to produce hourly indoor and outdoor PM 2.5 concentrations. Namely, for each monitor, we download 10-minute observations from the earliest available date through the end of 2020 or the last available date, whichever is later.…”

“…A large number of previous studies [e.g., (33,35,38,39) among many others] have focused on average indoor-to-outdoor concentration ratios (I/O) as a metric of infiltration. If measured over long time periods, this average I/O ratio does represent the net atmospheric barrier provided by a building, but is inclusive of emissions from indoor sources (which may be either trapped or ventilated) (60).…”

“…Using data from the American Time Use Survey, we calculate that Americans on average spend >70% of their time indoors at home, with higher shares for lower-income and elderly individuals and overall shares trending up over time (Fig S1). Personal integrated exposure to variation in ambient exposure is then likely substantially mediated by characteristics of home and work environments that are hard to observe (33)(34)(35), and these differences could in turn affect outcomes (36)(37)(38)(39). If socioeconomic or demographic variables shape indoor environments in ways that affect exposures, as has been hypothesized (37), then exposure levels or policy choices that appear equitable based on traditional outdoor measures could obscure large disparities in realized exposures.…”

Intercomparison Of PurpleAir Sensor Performance Over Three Years Indoors and Outdoors at a Home: Bias, Precision, and Limit of Detection Using an Improved Algorithm for Calculating PM2.5

“…These values are quite Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 9 February 2022 doi:10.20944/preprints202202.0142.v1comparable to those found in a previous study including 91 PurpleAir indoor monitors averaged over times from 796 hours to 13,564 hours. The observed means ranged from a median of 3.4 ug/m3 to a 75 th percentile value of 5.5 ug/m3[15].…”