The ‘Air Quality in Europe – 2016’ report of the European Environment Agency states that around 70,000 premature deaths were attributable to nitrogen dioxide (NO2) in Europe in 2013[1]. This makes NO2 next only to particulate matter as the most deadly air pollutant in Europe. The continuous monitoring of NO2 is, therefore, essential.
Measurements show frequent exceedances of the limits set in the European Air Quality Directive, leading to an official warning in February 2017 to five EU member states[3]. The EU Air Quality Directive also specifies chemiluminescence as the reference method for NO2 measurements[2].
To calibrate a chemiluminescence analyser, several methods can be employed including use of NO2 reference gas mixtures. VSL – the Dutch National Metrology Institute – produces NO2 standards by gravimetric methods using a highly accurate mass comparator. VSL provides primary reference standards for NO2 in nitrogen and air at 10-100 parts-per-million (2% uncertainty and 12 month stability) and 101-1000 ppm (1% uncertainty and 24 month stability).
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