Measurements of airborne particles have some similarities to those of gases, while bringing extra challenges. An international infrastructure to provide traceability for measurements of particle number concentration using condensation particle counters (CPCs) is currently being put in place. At low sizes (less than around 30 nm), results depend on the particle material. The use of silver nanoparticles is specified in PD CEN/TS 16976:2016 as the material for calibrating CPCs to be used for monitoring ambient air. Silver has a number of advantages over other materials such as the ability to generate particles with good morphology in the size range 5 to 20 nm. The National Physical Laboratory is developing a silver nanoparticle source with the aim of creating a stable, monodisperse source which can be used in these CPC calibrations. This capability is crucial in the running of the UK particle monitoring network, and also as a service to offer commercial clients. The background to this work will be discussed and results obtained so far presented.
Isabel is a Research Scientist in the Gas and Particle Metrology Group at NPL, working in the nanoparticles laboratory on a range of projects primarily based around air quality. Her role includes working with a variety of measurement instrumentation and carrying out calibrations on equipment such as Condensation Particle Counters (CPC) and Scanning Mobility Particle Sizers (SMPS). This work is for both commercial calibrations and to support the Defra Particle Number and Concentration Network. Isabel also runs the Defra Black Carbon Network, liaising with other organisations to ensure the smooth running of 14 monitoring sites across the UK and processing and reporting the data collected.