Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p72
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 72/108)
Character Range: 1092039–1095333

test shall consist of vehicle operation on a chassis dynamometer on the applicable WLTC for the interpolation family. A proportional part of the diluted exhaust emissions shall be collected continuously for subsequent analysis using a constant volume sampler.
              2.1.3. Background concentrations shall be measured for all compounds for which dilute mass emissions measurements are conducted. For exhaust emissions testing, this requires sampling and analysis of the dilution air.
              2.1.3.1. Background particulate measurement
              2.1.3.1.1. Where the manufacturer requests subtraction of either dilution air or dilution tunnel background particulate mass from emissions measurements, these background levels shall be determined according to the procedures listed in paragraphs 2.1.3.1.1.1. to 2.1.3.1.1.3. inclusive of this annex.
              2.1.3.1.1.1. The maximum permissible background correction shall be a mass on the filter equivalent to 1 mg/km at the flow rate of the test.
              2.1.3.1.1.2. If the background exceeds this level, the default figure of 1 mg/km shall be subtracted.
              2.1.3.1.1.3. Where subtraction of the background contribution gives a negative result, the background level shall be considered to be zero.
              2.1.3.1.2. Dilution air background particulate mass level shall be determined by passing filtered dilution air through the particulate background filter. This shall be drawn from a point immediately downstream of the dilution air filters. Background levels in g/m3 shall be determined as a rolling arithmetic average of at least 14 measurements with at least one measurement per week.
              2.1.3.1.3. Dilution tunnel background particulate mass level shall be determined by passing filtered dilution air through the particulate background filter. This shall be drawn from the same point as the particulate matter sample. Where secondary dilution is used for the test, the secondary dilution system shall be active for the purposes of background measurement. One measurement may be performed on the day of test, either prior to or after the test.
              2.1.3.2. Background particle number determination
              2.1.3.2.1. Where a manufacturer requests a background correction, these background levels shall be determined as follows:
              2.1.3.2.1.1. The background value may be either calculated or measured. The maximum permissible background correction shall be related to the maximum allowable leak rate of the particle number measurement system (0.5 particles per cm³) scaled from the particle concentration reduction factor, PCRF, and the CVS flow rate used in the actual test;
              2.1.3.2.1.2. Either the responsible authority or the manufacturer may request that actual background measurements are used instead of calculated ones.
              2.1.3.2.1.3. Where subtraction of the background contribution gives a negative result, the PN result shall be considered to be zero.
              2.1.3.2.2. The dilution air background particle number level shall be determined by sampling filtered dilution air. This shall be drawn from a point immediately downstream of the dilution air filters into the PN measurement system. Background levels