CDC spravilo novy vyskum respiratoroch FFP2
"Based on a sample size of 13 models, this study found that unmitigated FFRs with an exhalation valve that were tested in an outward position (with particles traveling in the direction of exhalation) have a wide range of penetration, emitting between <1% and 55%. Further testing could measure greater particle penetration.
Even without mitigation, FFRs with exhalation valves can reduce 0.35-µm MMAD particle emissions more consistently than surgical masks, procedure masks, cloth face coverings, or fabric from cotton t-shirts; however, the 0.35-µm MMAD particle emissions are not expected to be lower for every model.
With mitigations that cover the exhalation valve, 0.35-µm MMAD particle emissions can be limited to 5% if the filter media does not interfere with providing a good seal to the exhalation valve. The exhalation valves could be improved by establishing criteria for valve performance. Such criteria may be to maintain a plastic surface that is not obstructed with filter media or to have minimum and maximum outward leakage at given airflow conditions.
Covering an FFR with a surgical mask was not the most effective mitigation strategy evaluated here. The best mitigation strategy evaluated was to cover the exhalation valve inside the FFR with an ECG pad.
Securing surgical tape over the exhalation valve inside the FFR performed nearly as well as using the ECG pad. Researchers intentionally selected products with no expected toxicological effects in relation to skin contact, inhalation, and ingestion."
https://www.cdc.gov/niosh/docs/2021-107 ... 21-107.pdf
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