2.2.5. Artefacts

When comparing solid particle number concentrations, it has to be ensured that no artefacts take place. The volatile artefact is the formation, downstream of the evaporation tube, of volatile particles via re-nucleation of semi-volatile species in the measurement system [16,47]. These particles are volatiles but are counted as solids. The appearance of solid particles in the transfer line due to formation or growth in the transfer tube is defined as a nonvolatile artefact [14,15]. Artefacts at sub-23 nm particle measurements of mopeds and motorcycles have been reported in the literature [13,15]. The topic will not be further discussed; it should be noted though that due to the low exhaust gas temperatures and the high employed dilution in the SPN systems, we do not expect any artefacts in our results.
