Recent Developments in the Measurement of Low Particulate Emissions from Mobile Sources: A Review of Particle Number Legislations

Abstract

The combination of modern engine technologies, efficient aftertreatment, and tighter emission standards resulted in drastically lower particulate emission levels in Europe today. The conventional methods defined to test particulate emissions fail at such low levels as they are aimed at determining the mass of the particles collected on a filter (PM). This led to particle number (PN) measurement having become established as the method of choice to test for low particulate emissions from mobile sources. At present, there are several emission legislations that have added PN as an additional emission parameter, while there are no mandatory regulations for ambient air monitoring anywhere in the world so far. An overview of already enforced as well as an outlook of upcoming emission legislations for mobile sources that will require PN measurement will be given in this review and corresponding test solutions are described. Special emphasis is given to emission testing of construction machinery diesel particle filters in the field. Portable test equipment capable of measuring nonvolatile PN from such combustion sources is explained. Despite the progress, challenges in the measurement of low particle emissions remain, including the fact that solid particles that exist in the sub-23-nm-size range could be of more importance than originally thought.