How do we monitor air pollution?
Air pollution is monitored at certain sites around Scotland 24 hours a day. There are many different ways of sampling the air to check how polluted it is.
Ways to sample ambient air
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
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
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
- Data is sent from the site directly to your computer which means it can be seen instantly
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 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