[Investigation of the Filter Performance in a Sample of Standardised Particle-filtering Half Masks].

Background:  Thanks to a simplified special approval process that was valid until October 1st, 2020, a large number of particle-filtering half masks have come onto the German market. When caring for SARS-CoV-2 infected patients, the RKI recommends wearing particle-filtering half masks with a filter performance of at least 94 %, which corresponds to FFP class 2 according to EN 149:2001+A1:2009. We have examined 15 particle-filtering half masks with different specifications for their filter performance METHOD:  The masks were clamped in a jig in an airtight test box. Radioactive particles with a size of 0.6 ± 0.4 µm were nebulized into the box and sucked into a filter through the port of the jig and an unfiltered reference port using an artificial lung. The activity deposited on the filter was measured by means of a gamma camera. The filter performance was calculated from this.

Results:  Five of the 15 masks tested had a filter performance of less than 94 % and therefore do not meet the FFP2 standard. The filter performance of these masks was 71.8 ± 2.3 %, 73.2 ± 2.3 %, 78.2 ± 6.7 %, 92.2 ± 0.5 % and 85.9 ± 1.6 %.

Conclusion:  One third of the examined masks did not meet the recommended FFP2 standard, which is recommended for the care of SARS-CoV-2 infected patients. A comprehensive review of already approved products by the supervisory authorities is advisable.