Index: the UK Daily Air Quality Index (DAQI) on Defra's averaging: NO₂ 1-hour, O₃ 8-hour, PM₂.₅ and PM₁₀ 24-hour running means. A site's index is its highest pollutant index.
Hourly values are labelled by the end of the hour (12:00–13:00 is shown as 13:00). Dashed lines: UK objective, WHO 2021 guideline (AQG) and interim targets, and the borough target once Lewisham sets it.
Automated daily checks on every site and pollutant. Values are never changed: each finding is a flag beside the data, and the same flags appear in the qc_flag column of every download.
Data capture and findings by site
Findings
Check, in this browser, that the data on the chart are exactly what the sensors' raw data produced and have not changed since the day they were sealed. Nothing here relies on trusting this page: the same checks run in the free script verify_air_priori_data.py (Python 3; pip install requests pandas cryptography rfc3161ng).
One request returns everything selected, whatever the date range.