What is the Daily Air Quality Index?

The DAQI tells you about levels of air pollution. It also provides health advice in the form of recommended actions you may wish to take, according to the level of air pollution. The index is numbered 1-10 and divided into four bands, low (1) to very high (10), to provide detail about air pollution levels in a simple way. This system was recommended by the Committee on Medical Effects of Air Pollutants (COMEAP).

You should follow the 3 step method to use the index.

Defra applies the DAQI to its air quality forecasts to tell you what pollution levels are predicted to be the next day. The forecasts are provided to allow you to plan ahead and where relevant, take the recommended action to reduce the effects of air pollution. In addition, Defra's latest air pollution monitoring data are displayed using the same index and this tells you what pollution has been like.

The overall air pollution index for a site or region is determined by the highest concentration of five pollutants:

  • Nitrogen Dioxide
  • Sulphur Dioxide
  • Ozone
  • Particles < 2.5µm (PM2.5)
  • Particles < 10µm (PM10)

Boundaries Between Index Points for Each Pollutant

Use the tabs below to view the bandings for each pollutant.

Nitrogen Dioxide

Based on the hourly mean concentration.

Band Low Low Low Moderate Moderate Moderate High High High Very High
µg/m³ 0-67 68-134 135-200 201-267 268-334 335-400 401-467 468-534 535-600 601 or more

Additional information for data providers

Defra has written a report describing how the index has been implemented, including details on use of the running 24-hour mean for the latest monitoring data on UK-AIR and the use of triggers to predict air pollution episodes. This report describes updates to the thresholds used and may be of interest to air quality data providers.

You may also be interested in: