3 ms·SO2 and O3 sensors are very expensive, so almost all sensors made for homes measure PM.by xiphias2 6y agoSO2 and O3 sensors are very expensive, so almost all sensors made for homes measure PM.xxpor 6y agoIn that case it's almost certainly the highway. Tires are a massive source of PM2.5.akor 6y agoThat's my main concern although maybe air pollution from toast / allergens is just as bad.