Document ID: chunk:federal_register_of_legislation:F2024C00356:reg:20:p11
Version: federal_register_of_legislation:F2024C00356
Segment Type: reg
Provision Reference: reg 20 (pt 11/19)
Character Range: 254393–257501

the particle and hydrocarbon filters into the particle number measurement system. Background correction of particle number measurements shall not be allowed for type approval, but may be used at the manufacturer's request for conformity of production and in service conformity where there are indications that tunnel contribution is significant.
              6.2.6. Particulate mass filter selection
               A single particulate filter without back-up shall be employed for both urban and extra-urban phases of the cycle combined.
               Twin particulate filters, one for the urban, one for the extra-urban phase, may be used without back-up filters, only where the pressure-drop increase across the sample filter between the beginning and the end of the emissions test is otherwise expected to exceed 25 kPa.
              6.2.7. Particulate mass filter preparation
              6.2.7.1. Particulate mass sampling filters shall be conditioned (as regards temperature and humidity) in an open dish that has been protected against dust ingress for at least 2 and for not more than 80 hours before the test in an air-conditioned chamber. After this conditioning, the uncontaminated filters will be weighed and stored until they are used. If the filters are not used within one hour of their removal from the weighing chamber they shall be re-weighed.
              6.2.7.2. The one hour limit may be replaced by an eight-hour limit if one or both of the following conditions are met:
              6.2.7.2.1. A stabilized filter is placed and kept in a sealed filter holder assembly with the ends plugged; or
              6.2.7.2.2. A stabilized filter is placed in a sealed filter holder assembly which is then immediately placed in a sample line through which there is no flow.
              6.2.7.3. The particulate sampling system shall be started and prepared for sampling.
              6.2.8. Particle number measurement preparation
              6.2.8.1. The particle specific dilution system and measurement equipment shall be started and readied for sampling.
              6.2.8.2. Prior to the test(s) the correct function of the particle counter and volatile particle remover elements of the particle sampling system shall be confirmed according to Appendix 5, paragraphs 2.3.1. and 2.3.3.:
               The particle counter response shall be tested at near zero prior to each test and, on a daily basis, at high particle concentrations using ambient air.
               When the inlet is equipped with a HEPA filter, it shall be demonstrated that the entire particle sampling system is free from any leaks.
              6.2.9. Checking the gas analysers
               The emissions analysers for the gases shall be set at zero and spanned. The sample bags shall be evacuated.
              6.3. Conditioning procedure
              6.3.1. For the purpose of measuring particulates, at most 36 hours and at least 6 hours before testing, the Part Two cycle described in paragraph 6.1. of this annex shall be used for vehicle pre-conditioning. Three consecutive cycles shall be