Annex D(informative)Main test conditions for filtration efficiency test methodsTo determinate the filtration efficiency, it is recommended to apply the following parameters:a) Nature of the aerosol:— Solid particles (Sodium Chloride NaCl, Talcum powder, Holi powder, dolomite, PSL) are recommended,— Liquide particles (DEHS Di-Ethyl-Hexyl-Sebacat, parafin oil) are recommended.b) The filtration velocity shall be of 6 (± 1) cm/s.c) The upstream concentration should be at least 40 particles per cm3.d) The particle size shall be a monodisperse or polydisperse aerosol characterized by a sufficient 3 (± 0,5) µm particle concentration upstream of the test media.For measurement equipment a particle sizer is recommended to determine the number concentration of particles with a diameter around 3 µm. The technology of the instrument used and the type of equivalent diameter measured shall be specified in the test report.The results could be presented as average values.The determination of the filtration efficiency could be calculated as follows: With: Cupstream Cdownstream x100 C upstream Cupstream: the particle number concentration associated to particles denoting a diameter around 3 µm and measured upstream of the media composing the tested community face covering.Cdownstream: the particle number concentration associated to particles denoting a diameter around 3 µm and measured downstream of the media composing the tested community face covering.The test report shall include the set-up used (reference to standard if applicable) and parameters used for testing:— nature of aerosol;— airflow and sample size.