Document ID: chunk:federal_register_of_legislation:F2012C00283:reg:21:p29
Version: federal_register_of_legislation:F2012C00283
Segment Type: reg
Provision Reference: reg 21 (pt 29/39)
Character Range: 336760–339804

the ET shall be controlled to a wall temperature greater than or equal to that of the first particle number dilution device and the wall temperature held at a fixed nominal operating temperature between 300 °C and 400 °C, to a tolerance of ±10 °C.
              1.4.4.3. Second Particle Number Dilution Device (PND2)
               PND2 shall be specifically designed to dilute particle number concentration. The diluter shall be supplied with HEPA filtered dilution air and be capable of maintaining a single dilution factor within a range of 10 to 30 times. The dilution factor of PND2 shall be selected in the range between 10 and 15 such that particle number concentration downstream of the second diluter is less than the upper threshold of the single particle count mode of the PNC and the gas temperature prior to entry to the PNC is < 35 °C.
              1.4.5. Particle Number Counter (PNC)
               The PNC shall meet the requirements of paragraph 1.3.4.
              2. Calibration/validation of the particle sampling system[7]
              2.1. Calibration of the Particle Number Counter
              2.1.1. The Technical Service shall ensure the existence of a calibration certificate for the PNC demonstrating compliance with a traceable standard within a 12 month period prior to the emissions test.
              2.1.2. The PNC shall also be recalibrated and a new calibration certificate issued following any major maintenance.
              2.1.3. Calibration shall be traceable to a standard calibration method:
               (a) By comparison of the response of the PNC under calibration with that   of a calibrated aerosol electrometer when simultaneously sampling                             electrostatically classified calibration particles; or
               (b) By comparison of the response of the PNC under calibration with that   of a second PNC which has been directly calibrated by the above                             method.
               In the electrometer case, calibration shall be undertaken using at least six standard concentrations spaced as uniformly as possible across the PNC's measurement range. These points will 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. With no calibration factor applied to the PNC under calibration, measured concentrations shall be within ±10 per cent of the standard concentration for each concentration used, with the exception of the zero point, otherwise the PNC under calibration shall be rejected. The gradient from a linear regression of the two data sets shall be calculated and recorded. A calibration factor equal to the reciprocal of the gradient shall be applied to the PNC under calibration. Linearity of response is calculated as the square of the Pearson product moment correlation coefficient (R2) of the two data sets and shall be equal to or greater than 0.97. In calculating both the gradient and R2 the linear