Overview of Vehicle Exhaust Particle Number Regulations

Abstract

Vehicle emissions are a significant source of air pollution in cities. Particulate matter (PM) is a pollutant with adverse health effects. Regulations worldwide determine the PM exhaust emissions of vehicles by gravimetric quantification of the mass deposited on a filter over a test cycle. The introduction of particulate filters as vehicle exhaust gas aftertreatment devices led to low PM emissions. A particle number methodology (counting solid particles >23 nm), complementary to the PM mass measurement, was developed by the PMP (Particle Measurement Programme) group of the GRPE (Working Party on Pollution and Energy) of the UNECE (United Nations Economic Commission for Europe) during the first decade of the 21st century. The methodology was then introduced in the EU (European Union) regulations for light-duty (2011), heavy-duty (2013), and non-road mobile machinery (2019). In parallel, during the last 15 years, UN (United Nations) regulations and GTRs (Global Technical Regulations) including this methodology were also developed. To address the on-road emissions, the EU introduced RDE (real-driving emissions) testing with PEMS (portable emissions measurement systems) in 2017. Other countries (e.g., China, India) have also started adopting the number methodology. The PMP group recently improved the current laboratory and on-board methodologies and also extended them to a lower particle size (counting solid particles >10 nm). Due to the rapid evolution of the vehicle exhaust particle number regulations and the lack of a summary in the literature, this paper gives an overview of current and near future regulations. Emphasis is given on the technical specifications and the changes that have taken place over the years.

Emissions of Carbonaceous Particulate Matter and Ultrafine Particles from Vehicles—A Scientific Review in a Cross-Cutting Context of Air Pollution and Climate Change

“…They concluded that control policies for condensable particles and their precursors are needed to further reduce the vehicle-exhaust-derived PNs in the environment. The 23 nm lower size does not always cover the whole or the largest part of the size distribution of the emitted particles, as highlighted in a recent review [ 274 ] and references therein. High amounts of sub-23 nm particles are measured very often, both for diesel and gasoline direct-injection vehicles, but in particular for the technologies not subject currently to a SPN limit (port fuel injection gasoline and gas engines).…”

Experimental research on instrumentation for measuring automotive exhaust particle concentrations

“…However, with the increasing awareness of the harm of particulate emissions from vehicles [14,15], governments and environmental agencies have imposed more stringent regulations and standards for vehicle emissions, along with higher testing requirements, making particulate matter detection increasingly important. There has been a significant shift in recent years from traditional particle mass (PM) measurements to particle number (PN) measurements for particulate detection [16][17][18], with a particular focus on the quantity and size distribution of fine particles [18,19]. Therefore, the independent development of equipment suitable for measuring particulate number concentration in in-use vehicles in China is of great significance.…”

Assessment of two condensation particle counters (CPCs) in photometric mode for high concentration exhaust emission measurements

“…The PN method was introduced in the EU regulation for light-duty diesel vehicles in 2011. The PM and PN limits were extended to gasoline vehicles with direct injection engines, heavy-duty engines, and non-road mobile machinery (NRMM) [2,3]. A similar method has also been proposed for measurement of particles from brake emissions [4].…”

“…CPCs are instruments that optically count particles using light scattering after their growth to micron size in a supersaturated environment [9,10]. The CPCs of the laboratory systems have strict linearity requirements (±5%), while the PEMS more relaxed (±15%) [2].…”