# Commission Regulation (EU) 2017/1151 of 1 June 2017 supplementing Regulation (EC) No 715/2007 of the European Parliament and of the Council on type-approval of motor vehicles with respect to emissions from light passenger and commercial vehicles (Euro 5 and Euro 6) and on access to vehicle repair and maintenance information, amending Directive 2007/46/EC of the European Parliament and of the Council, Commission Regulation (EC) No 692/2008 and Commission Regulation (EU) No 1230/2012 and repealing Commission Regulation (EC) No 692/2008 (Text with EEA relevance), Division 5.7.2: Calibration/validation of the VPR


Nin(di) and Nout(di) shall be corrected to the same conditions.
The arithmetic average particle concentration reduction factor fr– at a given dilution setting shall be calculated using the following equation:
fr–=fr30nm+ fr50nm+ fr100nm3
Where a polydisperse 50 nm aerosol is used for validation, the arithmetic average particle concentration reduction factor fv– at the dilution setting used for validation shall be calculated using the following equation:
fv–=NinNout
where:
Ninis the upstream particle number concentration;
Noutis the downstream particle number concentration.

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Source: https://www.legislation.gov.uk/eur/2017/1151/annex/Sub/5/division/division/5./division/5.7./division/5.7.2. (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-1151/annex-Sub/5/division/division-5./division-5.7./division-5.7.2.
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.