Laboratory measurements with solid particle number instruments designed for periodic technical inspection (PTI) of vehicles

Abstract

Particulates emitted by vehicles can be significantly reduced with the use of particulate filters. In some European countries, the control of these filters’ efficiency during their lifetime is done with a recently introduced solid particle number (SPN) test at low idling performed during periodic technical inspection (PTI) of Diesel vehicles. This paper examines the counting efficiency, linearity, and volatile removal efficiency of seven SPN-PTI instruments with laboratory-based particle generators and with vehicle exhaust. Some challenges related to low monodisperse particles concentration were identified during counting efficiency tests and discussed in view of type examination procedures. In agreement with the current metrological requirements, the maximum error (i.e., deviation from reference) of all instruments at linearity checks was < 25 % in a wide range of concentrations when testing with carbonaceous particles but error levels depended on the particle material used for testing. Finally, tetracontane removal efficiency of all instruments was > 95 %.