Study of the uncertainty in NO₂ chemiluminescence measurements due to the NO-O₃ reaction in sampling lines
2011
Miñarro, Marta Doval | Ferradás, Enrique González | Rico, Jonathan Barberá | Alonso, Fernando Díaz | Martínez, Francisco J Marzal | Trigueros, Cristina Romero
Introduction The change in light intensity that takes place when an ambient air sample is drawn into the detection chamber of a chemiluminescence monitor generates changes in the concentrations of several species, such as NO₂, NO and O₃. Although this phenomenon has been known for several decades, there is still no commonly accepted approach on when or how to correct for it in NO₂ and O₃ readings. Discussion In this work, we have assessed the expanded uncertainty of two chemiluminescence NO x analysers commercially available according to EN 14211:2005, with the aim of establishing the maximum allowable standard uncertainty due to the reaction between NO and O₃ in the sampling system. Conclusion Although this maximum allowable uncertainty cannot be a universal value--as it will depend on the performance of each analyser--our results have led us to propose the conservative value of 2%. We have also proposed a methodology for improving data quality which could be easily implemented by those responsible for air quality data validation.
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