Measuring air quality

There are four main methods for measuring air pollution: passive sampling methods, active sampling methods, automatic methods, remote optical/long path-analysers.

In the case of passive sampling methods, the flow of air is controlled by a physical process, such as diffusion. Active sampling methods use physical or chemical methods to collect polluted air and analysis is carried out later in the laboratory. Automatic methods produce high-resolution measurements of hourly pollutant concentrations or better, at a single point. Pollutants analysed include ozone, nitrogen oxides, sulphur dioxide, carbon monoxide and particulates. Remote optical/long path-analysers use spectroscopic techniques, make real-time measurements of the concentrations of a range of pollutants including nitrogen dioxide and sulphur dioxide.


NODES strategic objectiveContribution
Enhance accessibility and integration 0
Enhance intermodality 0
Enhance liveability ++
Increase safety and security conditions 0
Increase economic viability and costs efficiency 0
Stimulate local economy 0
Increase environmental efficiency +
Increase energy efficiency +

Good practice


Because of the bad air quality near trains in California, there are different measures for improving the air quality. These include installing particle filters.

Improvement of air quality in Barcelona metro system

The overall aim of IMPROVE is to provide a benchmark study that will lead to real improvement in subway air quality. It has made in January 2015 its first steps installing air quality measuring equipment at a station on the Line 5 of the Barcelona system. From now on until September 2016, a dozen campaigns will be held to collect samples at various points of the metro in Barcelona. The concentration levels of airborne suspended microparticles (PM) as well as their chemical composition will be determined both at stations and inside the trains. Measurements will be done both under normal situations and when performing activities that generate dust, such as the renovation work of the track, which take place regularly.



Potential interchange performance improvement

  • assessing public health impacts caused by poor air quality
  • determining whether an area is meeting the standards
  • evaluating changes in air quality as a result of state implementation plans


The costs for air quality measuring methods are very different. Costs depend on how the air is measured and what equipment is required for the different methods.

If the measures detect certain pollutants, further costs may arise in order to implement possible solutions.



This link of the local air quality managament (LAQM) provides several links to good practice sites and gives further detailed information: