Monitoring air pollution

Salford City Council has a long history of monitoring air pollution. The data is used for:

  • air quality review and assessments undertaken by Salford City Council and the Greater Manchester Combined Authority
  • demonstrating progress in meeting air quality standards
  • evaluating the impact of air quality action plan measures and other measures
  • determining air quality trends and highest pollutant concentrations
  • evaluating the effects of air pollution on public health
  • improving the accuracy of air quality modelling and forecasting
  • providing information for the public to engage with local air quality issues and measures taken to improve it 

Air pollution monitoring activity can be split into two categories:

1. Automatic monitoring

Automatic monitoring

Automatic monitoring involves the use of electronic monitoring instruments capable of giving almost real-time concentrations of pollutants. The instruments are operated to rigorous quality standards, independently audited to national standards and run continuously. They record the concentration of the pollutant they are measuring and store the results.

There are three automatic air quality monitoring sites in Salford:

Automatic monitoring site Air quality pollutants currently monitored
M60: a roadside monitoring site located close to the M60 in Worsley
  • Oxides of nitrogen (NOX, NO and NO2)
  • Particles (PM10 and PM2.5)
  • Ozone (O3)
Eccles: an urban background site located close to Eccles town centre
  • Oxides of nitrogen (NOX, NO and NO2)
  • Particles (PM10 and PM2.5)
  • Polyaromatic Hydrocarbons (PAH) 
Glazebury: a rural background site run by the Department for Environment and Rural Affairs (DEFRA)
  • Oxides of nitrogen (NOX, NO and NO2)
  • Ozone (O3)

Automatic monitoring site data:

Detailed historical data from all three monitoring sites can be downloaded from the Air Quality England website. Data from these sites and other automatic monitoring sites within Greater Manchester can also be downloaded from the Clean Air Greater Manchester website.

2. Non-automatic monitoring

Non-automatic monitoring is less sophisticated and cannot give real time results, but is cheaper to use and provides a wide coverage of measurements in different types of settings. Salford City Council currently has a monitoring network of over 40 passive diffusion tubes at locations across the city, that detect levels of nitrogen dioxide (NO2) by absorption. Monitoring in Salford is carried out according to government technical guidance and following rigorous quality control procedures in terms of storage, deployment, analysis and data reporting.

Diffusion tube bias adjustment:

Diffusion tubes are changed over monthly and sent to an independent UKAS accredited laboratory for analysis. Each year, the laboratory results are corrected for bias by comparing them to more sophisticated automatic analyser results. The correction factor is applied to the diffusion tubes in our network, and then the corrected results are used to compare the annual average to the national air quality objective for NO2. This is the standard way of using diffusion tubes across the UK. Further information on bias correction is available from Department for Environment and Rural Affairs (DEFRA).

Diffusion tube monitoring site data:

Bias adjusted annual average results since 2011 from the current diffusion tube network in Salford can be downloaded from the Clean Air Greater Manchester website.

Air quality modelling:

It is not practicable to carry out air quality monitoring on every road, and so the monitoring is supplemented by computer dispersion modelling. The latest industry standard modelling software is used and takes into account factors such as road traffic, rail movements, industrial stack emissions, background emissions (such as emissions from domestic and commercial heating systems) and weather data to predict pollutant concentrations over a wide area. Dispersion modelling can also predict concentrations under different situations, for example in the future or as a result of new policy scenarios.

Further information

Monitoring sites map:

An online and interactive map is available to view the locations of current air quality monitoring sites in Salford. The AQMA is also shown on the map.

The location of air pollution monitoring sites within Greater Manchester can be viewed on the Clean Air Greater Manchester website.

Current air quality, forecast and alerts

Daily air quality monitoring results, a free sign up service for air pollution alerts and a local air quality forecast for up to the next three days are available from Clean Air Greater Manchester.

Downloadable documents

If you are unable to view documents of these types, our downloads page provides links to viewing software.

This page was last updated on 20 April 2022

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