A view of the San Francisco Bay Area from Berkeley Lab during the 2018 Camp fire (left) and three weeks prior. The graphs show PM2.5 concentrations (microgram per cubic meter), with the x-axis as measured by the regulatory monitor in downtown Berkeley and the y-axis as measured by PurpleAir monitors. On the good air day, the numbers were roughly the same. However, when wildfire smoke was present the PurpleAir readings were consistently far higher than the regulatory monitor's. (Photo credit: Kelly J. Owen/B
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