This document specifies a method for the sampling of NO2 in ambient air using diffusive sampling followed by extraction and analysis by colourimetry or ion chromatography (IC). It can be used for the NO2 measurement in a concentration range of approximately 3 µg/m3 to 130 µg/m3 [12]. A sample is typically collected for a period of 1 to 4 weeks [14], with exposure periods depending on the design of the samplers and the concentration levels of NO2.
Several sorbents can be used for trapping NO2 in ambient air using a diffusive sampler [15]. This document specifies the application of triethanolamine as the reagent.
This document describes the application of a tube-type sampler (with either a cylindrical or a slightly conical tube), a badge-type sampler and a radial-type sampler.
The relative expanded uncertainty of NO2 measurements performed using these tube-type diffusive samplers can potentially be lower than 25 % for individual measurements. When aggregating results to form annual average values, the relative expanded uncertainty can be further reduced to levels below 15 % due to the reduction of random effects on uncertainty [9].
NOTE NO2 passive samplers are also employed to measure NOx with the addition of an oxidant to convert ambient NO into NO2. A second NO2 sampler is also deployed without the oxidant and the concentration of NO is determined from the difference of the two samplers [16].