yup. not entirely useless, but especially for the borderline yellow/orange AQI you want to know the error. http://www.aqmd.gov/aq-spec http://www.aqmd.gov/aq-s

yup. not entirely useless, but especially for the borderline yellow/orange AQI you want to know the error. http://www.aqmd.gov/aq-spec http://www.aqmd.gov/aq-spec tests and compares commercial AQM vs lab grade instruments. It isn't quite enough to compare a commercial unit with the same sensor, because you don't really know the mfr calibration (if any), but this will get you a much better idea of performance. i personally prefer to have a commercial sensor that has an API, rather than DIY.