Monitoring sites may be closed for a number of reasons which are not recorded on a case-by-case basis here. These include:
- Concentrations are consistently well below objectives so monitoring is no longer required at a particular location.
- The overall statutory minimum number of monitoring sites is reduced due to general declining concentrations of some pollutants e.g. sulphur dioxide and carbon monoxide.
- The site was only established for a short-term investigative study, e.g for an environmental impact assessment.
Historical data and statistics for closed monitoring sites can still be accessed by clicking the link even though they no longer report data for the real-time information services.