Data Archive

Data Tools

Introduction to monitoring data

There are three types of data stored in this section and these are outlined below.

1. Monitoring data

There are over 1500 sites across the UK that monitor air quality. They are organised into networks that gather a particular kind of information, using a particular method. There are two major types - automatic and non-automatic networks. The Monitoring Networks section provides further network information. Download data from the networks using the Data Selector Tool or download raw automatic data using the preformatted files link.

2. Descriptive statistics

For each monitoring site you can select a range of statistics which are relevant to the particular monitoring method. Basic statistics are annual mean, maximum and minimum values, with daily means, monthly means and a range of percentile values available where these are meaningful. Data from the UK Urban NO2 Network can be found using this option.

3. Exceedance statistics

Exceedance statistics provide information about concentrations above a specific threshold value. The exact concentration and the metric used varies by pollutant and purpose. A selection of commonly used examples are the UK Air Quality Objectives, EU Limit and Target Values, Critical Loads, the health-effects based system of four bands and a 1-10 index and the Indicators of Sustainable development - the average number of days per site on which pollution levels were above National Air Quality Standards.

These links will provide more information on the UK and EU Objectives and Limits and the Air Pollution Index and Banding System.

You can select any of these exceedance statistics for a range of time periods, pollutants and locations.

Ammonia Data 2022-2023

The ALPHA data on the National Ammonia Monitoring Network is being reissued for the years 2022 and 2023 due to a change in uptake rate applied. The change in uptake rate leads to an increase in reported concentration from ALPHAs of 21.9% and 40.6% for 2022 and 2023, respectively. Data will be available across UK-AIR once processed. Please refer to the NAMN page for further details.

Ambient ozone concentrations from 1 January 2025

Ambient ozone concentrations are measured by UV photometry (EN 14625:2012 'Ambient air quality - standard method for the measurement of the concentration of ozone by ultraviolet photometry' (CEN, 2005a)).

The method passes light at wavelength 253.65 nm (from a Hg lamp) through a reaction cell containing the sampled air and measures the drop in intensity caused by the absorption of the light by the O3 molecule. The calculation of the concentration of O3 in the sampled air involves a constant – the 'absorption cross section' of O3 at the relevant wavelength. This constant has been updated by the BIPM (the international bureau of weights and measures) and reflected within the updated CEN reference method EN14625:2024.

This will be applied to all data from 1 January 2025, resulting in an increase of ~1.24% and will dramatically improve measurement uncertainty.

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