Throughout the years, the performance of the FFRs has been the topic of extensive studies, resulting mainly in the characterization of aerosol penetration through filters using aerosols that are thought to be similar to those encountered in workplaces. There are limited number of studies in the literature reporting CE-marked respirator performance, and there is a need to perform a penetration evaluation of CE-marked respirators through all 3 filtering classes: FFP1 (80%), FFP2 (94%), and FFP3 (99%). In this study, the percentage penetrations and the most penetrating particle size (MPPS) of 47 mm filters cut out from 13 different CE-marked respirator half masks (2 samples of each FFR) were evaluated size-selectively using nine sizes of charge-neutralized monodisperse aerosol, which ranged from 20 to 400 nm (CMD). Comparison of the penetrations at MPPS from all the examined filters showed that the percentage penetration ranged 3.2–16.3% (FFP1), 2.4–34.3% (FFP2), and 0.02–3.3% (FFP3). Experimental data also revealed that the penetration difference between 2 samples from the same respirator was in most cases up to 6.8%, and between 2 identical respirators up to 2.5%. The MPPS was found to be between 30 and 60 nm (CMD) in all measurements. By comparing the obtained results to the European Standard we conclude that the standard method underestimates particle penetration (especially for particles < 100 nm) due to the usage of non neutralized, polydisperse test aerosol, detection methods burdened with measurement artifacts, and the assumption that the MPPS is at ≈ 600 nm (MMD) as the criterion for filtering facepieces to pass the penetration test.