Data from "low cost" PM (Particulate Matter) Luftdaten sensors in Bristol. These are not owned or maintained by Bristol City Council, but by individuals. The data are indicative and not to the same quality standard as air quality data supplied by the council. Data have been processed to give an hourly average from the raw data and timestamped with the hour ending the measurement timestamp. Data are updated daily at midnight and when the monthly data are made available at the luftdaten archive this dataset is updated with that file to cover any gaps that may be caused by glitches in the automatic update process.