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I'm not sure I get what you're saying here, HEPA is a standard that was developed for medical environments & clean rooms [1]. To qualify as HEPA, a filter shoul

I'm not sure I get what you're saying here, HEPA is a standard that was developed for medical environments & clean rooms [1]. To qualify as HEPA, a filter should be able to remove 99.97% of particles 0.3µm and above so it is definitely impacting PM2.5 (particles 2.5µm and below). See my other comment [2] for my opinion on smartair solutions. [1] https://en.wikipedia.org/wiki/HEPA https://en.wikipedia.org/wiki/HEPA [2] https://news.ycombinator.com/item?id=17720802 https://news.ycombinator.com/item?id=17720802

staikken 8y ago
I was under the impression that the filtration efficiency by particle size for such a filter was not a linear relationship.[0] So manufacturing to a lower bound of 3 may not say much for particles even slightly smaller. My estimation of the magnitude of this effect may be off however as this company seems to suggest. [0]https://www.globalspec.com/learnmore/manufacturing_process_equipment/filtration_separation_products/hepa_filters_ulpa_filters https://www.globalspec.com/learnmore/manufacturing_process_e...