Improved vehicle exhaust quantification by portable emission measurement systems metrology

European legislation sets limits on Nitrogen Oxides (NO_x) and fine particle number (PN) emitted from vehicle exhausts which are a leading cause of air pollution. Conformity factors establish not-to-exceed limits for PN and NO_x for on-road tests compared to laboratory tests and from 2020 new conformity factors will apply. On-road tests are performed using portable emission system (PEMS) instruments which allow real-world testing but lack full performance and metrological characterisation. There is therefore a need for calibration standards and guidelines that are currently not available.

The project has developed new standards and calibration procedures for the three key components of a PEMS system: determination of NO_x concentrations, number of particulates (PN) and exhaust mass flow. Based on these new measurements an improved PEMS instrument will be developed and validated along with traceable methods to extend performance for NO₂ concentrations below 10 μmol/mol and up to 2500 μmol/mol.

The work is expected to support the comparability of air quality measures across the EU and help manufacturers conform to current and future legislation.