Air pollution is monitored at certain sites around Wales 24 hours a day. There are many different ways of sampling the air to check how polluted it is.
There are 5 main methods of sampling air quality:
1
Passive Monitoring
- Diffusion tubes absorb a specific pollutant from the ambient air - no power supply is needed
- Diffusion tubes normally monitor for 2-4 weeks at a time
- The tubes must be sent to a laboratory for analysis to see how much pollution they have detected
- Semi-automatic sampling
2
Active (Semi Automatic) Sampling
- An analyser pulls the ambient air through a filter for a set period of time e.g one filter per day
- The filters are then collected and sent to a laboratory for analysis to see how much pollution they have detected
- Automatic monitoring point
3
Automatic point monitoring
- Ambient air is pulled through an analyser which recognises the chosen gas and will calculate its concentration
- Automatic sites monitor pollutants 24hours a day
4
Photochemical and optical sensor systems
- These are portable monitoring tools that can continuously monitor a range of pollutants. The sensors are of low sensitivity and mostly suitable for identifying hotspots at roadsides and near point sources.
- Data can be downloaded to your computer and analysed.
5
Remote optical/long-path monitoring
- This method of sampling detects pollution between a light source and a detector which are placed separately at a site
- Real time measurements can be taken with this type of sampling.
- Data can be sent from the analyser directly to your computer which means it can be seen instantly.