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Air quality monitoring network

Use this page to find out about air quality monitoring in the Bath and North East Somerset area.

Monitoring sites and pollutants

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

  • Nitrogen Dioxide
  • Particular Matter (PM)
  • Benzene

For additional up to date monitoring information view the UK Air Quality Archive.

Select a topic below to find out more:

Nitrogen Dioxide

Nitrogen dioxide (NO₂) is one of the most dangerous of the oxides of nitrogen to human health. It can cause inflammation of the airways and increased susceptibility to allergens and respiratory infections. It also exacerbates the symptoms of lung and heart conditions. 

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.

  • Diffusion tubes - which provide monthly average concentrations. Currently around 160 in Bath & North East Somerset.
  • Continuous analysers which measure the oxides of nitrogen using chemi-luminescence.

Particulate Matter (PM)

Particulate matter (PM) is classified according to size:

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

PM is hazardous to human health. It can penetrate deep into the lungs and bloodstream. It can aggravate asthma and other respiratory symptoms as well as decrease lung function. This increases hospital admissions and long term exposure can decrease lifespan.


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.

Benzene is detrimental to human health. It is a known carcinogen and can reduce the production of red and white blood cells. It can also be a moderate eye and skin irritant.

Monitoring sites

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

Live data

View the Air Quality Forecast for a more detailed interactive view of the UK Air Pollution Forecast for up to 5 days ahead.