Purchase of SMPS (Scanning Mobility Particle Sizer)

The SMPS (Scanning Mobility Particle Sizer) is used to measure aerosol concentration and aerosol particle size distribution. The system comprises of an Electrostatic Classifier (EC), a Differential Mobility Analyser (DMA), a Condensation Particle Counter (CPC), and an Aerosol Neutraliser.

They have been identified needing replacement in 2021-22 because there are no longer spare parts available from the manufacturer, and they are nearing the end of their useful life. They are difficult to communicate with as the technology for their communication systems is out of date and cannot be upgraded. We would not be compliant if they fail completely with Current UK Air Quality Legislation, which asks for information on the total mass concentration of particulate matter, and also for the purpose of the European Monitoring and Evaluation Programme (EMEP - part of the Convention on Long Range Transboundary Air Pollution (CLRTAP) which requires monitoring of particle number concentration).

In addition to the replacement of the components, a new sampling system is also required with driers and splitters that will replace the current system. Historically the old system has not performed and data capture loss is high. Additional a Butanol stripper will be purchased that will improve the life of the pump and minimise risks to the site users as Butanol will no longer be at risk of 'leaking' from the outlet pipes that should be vented outside the cabin, as it will be stripped as part of the sampling process. This has historically caused unwelcome smells for site users and interfered with other measurements.

The National Monitoring -Contracts, Monitoring Survey Team manage the Operational contracts on behalf of DEFRA on the PCN (Particle Size and Concentration) Network run by NPL (National Physical Laboratory) and Imperial College London - who will be able to deliver their management contract with the new equipment to a higher standard and with far less data loss than currently.

The upgrade is also well time for a change in the standard monitoring CEN standard which will result in a change of 'cut off' from 7nm to 10nm for measurements. The replacement will be for all 3 existing locations. Only TSI currently offer this new CEN Condensation Particle Counter component complies with CEN/TS 16976 and another Differential Mobility Analyser component complies with ISO 15900:2020.