Comparison of mask and respirator filtration test methods

NIOSH has issued a federal registration notice to explore the possibility of incorporating FDA-required mask (SMs) filtration tests into the 42 CFR Part 84 respirator certification process. No published study compares the NIOSH-certified filtration efficiency test method for the N95 filter mask respirator (N95 FFR) with the FDA's method for removing SM.

To solve this problem, the filtration efficiency of "N95 FFR”, including six N95 FFR models and three surgical N95 FFR models and three SM models, was measured using the NIOSH NaCl aerosol test method, while the FDA required particle filtration efficiency (PFE) and bacterial filtration efficiency (BFE) methods and viral filtration efficiency (VFE) methods. Use each method to test five samples of each model.According to FDA guidance documents, both PFE and BFE tests are carried out using un-neutralized particles. PFE was measured using polystyrene latex particles of 0.1 µm size and BFE and particles of about 3.0 µm size.Staphylococcus aureus bacteria. VFE was obtained using particles of about 3.0 µm in size containing phiX 174 as an attack on viruses and E. coli. As the host.The results showed that the "N95 FFR” efficiency measured by the NIOSH NaCl method was 98.15-99.68%, while the PFE, BFE was 99.62-99.9% and the VFE method was 99.8-99.9%. The efficiency of the NIOSH NaCl method is significantly lower than that of other methods (p = <0.05). The SM efficiency measured using the NIOSH NaCl method was lower (54.72–88.40%) than the "N95 FFRs”, while there was no significant difference between the PFE, BFE and VFE methods.

The above results show that, NIOSH NaCl method is relatively conservative, it is possible to identify poor performance of the filter device. The higher efficiency obtained using PFE, BFE and VFE methods shows that the addition of these supplementary particle penetration methods does not improve respirator certification.