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Measurement of particle number was introduced in the Euro 5/6 light duty vehicle emissions regulation. Although particle number measurement systems have to be calibrated by the manufacturers, labs have to validate the proper operation of their systems within one year of the emissions test. The systems must achieve a >99% reduction of an aerosol containing 30 nm tetracontane (CH3(CH2)38CH3) particles (C40) with an inlet concentration >104 #/cm3. They must also include an initial heated dilution stage with dilution of at least 10 which outputs a diluted sample at a temperature of 150°C–400°C. The system as a whole must achieve a particle number concentration reduction factor for particles of 30 nm and 50 nm electrical mobility diameters, that is no more than 30% and 20% respectively higher, and no more than 5% lower than that for particles of 100 nm.

A test programme designed to investigate the influence of gasoline vapour pressure and ethanol content on evaporative emissions from modern passenger cars was carried out by the Joint Research Centre of the European Commission together with CONCAWE and EUCAR. Seven gasoline passenger cars representative of current EURO 3/4 emissions technology were tested for evaporative emissions with ten different test fuels. The test fuel matrix comprised 60 and 70 kPa hydrocarbon base fuels with 5 and 10% ethanol splash blends and 5 and 10% ethanol matched volatility blends. The test protocol was based on the European homologation test procedure. Although the test protocol turned out to have a significant influence on the results, the programme provided valuable information and it was possible to draw several clear conclusions.