Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p62
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 62/108)
Character Range: 1061376–1064561

The linearity verification shall be performed at least every 12 months or whenever a system repair or change is made that could influence the calibration.
              5.7. Calibration and validation of the particle sampling system
              Examples of calibration/validation methods are available at: http://www.unece.org/trans/main/wp29/wp29wgs/wp29grpe/pmpFCP.html
              5.7.1. Calibration of the PNC
              5.7.1.1. The responsible authority shall ensure the existence of a calibration certificate for the PNC demonstrating compliance with a traceable standard within a 13-month period prior to the emissions test. Between calibrations either the counting efficiency of the PNC shall be monitored for deterioration or the PNC wick shall be routinely changed every 6 months if recommended by the instrument manufacturer. See Figures A5/16 and A5/17. PNC counting efficiency may be monitored against a reference PNC or against at least two other measurement PNCs. If the PNC reports particle number concentrations within ±10 per cent of the arithmetic average of the concentrations from the reference PNC, or a group of two or more PNCs, the PNC shall subsequently be considered stable, otherwise maintenance of the PNC is required. Where the PNC is monitored against two or more other measurement PNCs, it is permitted to use a reference vehicle running sequentially in different test cells each with its own PNC.
       Figure A5/16
       Nominal PNC annual sequence

Figure A5/17
Extended PNC annual sequence (in the case that a full PNC calibration is delayed)
              5.7.1.2. The PNC shall also be recalibrated and a new calibration certificate issued following any major maintenance.
              5.7.1.3. Calibration shall be undertaken according to ISO 27891:2015 and shall be traceable to a national or international standard by comparing the response of the PNC under calibration with that of:
                  (a) A calibrated aerosol electrometer when simultaneously sampling electrostatically classified calibration particles; or
                  (b) A second full flow PNC with counting efficiency above 90 per cent for 23 nm equivalent electrical mobility diameter particles that has been calibrated by the method described above. The second PNC counting efficiency shall be taken into account in the calibration.
              5.7.1.3.1. For the requirements of paragraphs 5.7.1.3.(a) and 5.7.1.3.(b), calibration shall be undertaken using at least six standard concentrations across the PNC's measurement range. These standard concentrations shall be as uniformly spaced as possible between the standard concentration of 2,000 particles per cm³ or below and the maximum of the PNC's range in single particle count mode.
              5.7.1.3.2.  For the requirements of paragraphs 5.7.1.3.(a) and 5.7.1.3.(b), the selected points shall include a nominal zero concentration point produced by attaching HEPA filters of at least Class H13 of EN 1822:2008, or equivalent performance, to the inlet of each instrument. The gradient from a linear least squares regression of the two data sets shall be calculated and recorded. A calibration