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kitcat 发表于 2020-2-3 21:09 
你漏看了一条:BFE (Bacterial Filtration Efficiency) > 99% and PFE (Particle Filtration Efficiency) ...
不是我漏看了,N95是针对0.3um的颗粒,BEF测试用的是3.0 ± 0.3 µm。完全不是一个量级的。N95能达到BEF 99.
摘一段wiki上解释N95的:
block 95% of particles 0.3 μm or larger in diameter, which include PM2.5. They are insufficient to stop most dry individual viruses, which typically range from 0.004 to 0.3 μm, but many viruses only survive in droplet of watery fluid (e.g., sputum), which may be blocked by a mask.
普通外科口罩,不用NIOSH评级,都是BEF 95或者BEF99,wiki上说不建议用在高风险场合:
Plain surgical masks are standard for staff in hospital operating rooms, and often recommended to the public as part of avoiding seasonal flu.[4] They do not carry a NIOSH rating. They are designed to filter out relatively large particles, such as sputum droplets and hair – but the World Health Organization, Society for Healthcare Epidemiology of America, the Infectious Diseases Society of America, the Association for Professionals in Infection Control and Epidemiology, and the American College of Occupational and Environmental Medicine all recommend these except in cases of "high risk"
BEF测试方法:
The aerosol droplets are drawn through a six-stage Andersen sampler for collection. The number of bacterial aerosol droplets contacting the filter media is determined by conducting challenge controls without filter medium in the test system. Challenge controls are maintained at 1700 – 3000 colony-forming units (CFU) with a mean particle size (MPS) of 3.0 ± 0.3 µm. This allows filtration efficiencies to be reported up to >99.9%. |
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