We operate a number of different monitoring sites that measure the following pollutants:

Nitrogen Dioxide

Nitrogen dioxide (NO2) is one of the most dangerous of the oxides of nitrogen to human health. It can be directly released into the environment or formed in secondary reactions in the atmosphere.

The main sources of nitrogen dioxide in the UK are road transport, energy generation and domestic and industrial combustion.In Bath and North East Somerset two methods to monitor Nitrogen Dioxide are used.

Particulate Matter (PM)

Particulate matter (PM) is classified according to size:

  • PM10 is particles that are less than or equal to 10 micrometres (µm) in diameter
  • PM2.5 is particles that are less than or equal to 2.5 micrometres (µm) in diameter

Particulate matter has a number of sources, both natural (sea spray and desert dust) and human made (smoke from fires and dust from tyres and brakes).

Primary PM is directly emitted from the source, whereas Secondary PM is formed in the atmosphere through chemical reactions between other pollutants.

BAM Tape


Benzene (C6H6) is a complex compound of carbon and hydrogen which is a liquid at room temperature but readily evaporates to emit small amounts into the atmosphere. Benzene concentrations measured on London Road (Bath) have been lower than the Government objective of 5 micrograms per cubic metre (µg/m3) at all times. Results from the Benzene monitoring are available on the UK-Air website.

Monitoring Sites

We operate four continuous monitoring sites providing up to date information on various pollutants.

  • Bath A4 Roadside* (London Road enclosure) - nitrogen dioxide, benzene and particulate matter (PM10)

  • Chelsea House (enclosure at junction with Snow Hill) - particulate matter (PM2.5) and nitrogen dioxide

  • Guildhall - nitrogen dioxide

  • Windsor Bridge (enclosure at Lower Bristol Road junction with Windsor Bridge Road) - nitrogen dioxide and particulate matter (PM10)

*For up to date monitoring information from the UK Air Quality Archive visit their website at  http://uk-air.defra.gov.uk.

Monitoring enclosure at Lower Bristol Road nr Windsor Bridge NO2 diffusion tube on a lamppost in Odd Down, Bath

For monitoring data, click on the following links:

 - Live air quality data

 - Long term air quality data

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