Great new study on #HEPA air cleaners by Lindsley et al. out today via @CDCMMWR: masks reduced aerosol by 72%, HEPA by 65%, together by 90%.
Conclusions are consistent with messages for months, but important that #CDC amplifying this strategy.
Short 🧵
cdc.gov/mmwr/volumes/7…
2/ "The use of masks without air cleaners reduced the aerosol exposure of the receivers by 72%, and the use of air cleaners without masks reduced the exposure by up to 65%. When used together, the HEPA air cleaners and masks reduced exposure to respiratory aerosols by up to 90%."
3/ "These findings suggest that the use of portable HEPA air cleaners and universal masking can each reduce exposure to simulated SARS-CoV-2 aerosols in indoor environments, with larger reductions occurring when air cleaners and masking are used together."
cdc.gov/mmwr/volumes/7…
4/ The study used simulated SARS-CoV-2 aerosol emitted from a manikin in a fixed location, w/ two portable HEPA cleaners at varied locations in room. Also tested w/ & w/out mask use. Always caveats & limitations, but study highlights importance of both masks & room filtration.
5/ The #MMWR report references several other studies to show similar efficacy of HEPA filters, e.g. the Curtius et al. study showing 90% reduction of aerosol w/in 5 min. in a classroom in Germany.
6/ And the study by Burgmann & Janoske "Transmission and reduction of aerosols in classrooms using air purifier systems"
aip.scitation.org/doi/10.1063/5.…
7/ The study could have also cited, among others, the nice, recent study by @KirstyBuising @RobynSchofield3 et al. showing reduction of aerosol in a hospital.
"Use of portable air cleaners to reduce aerosol transmission on a hospital COVID-19 ward"
cambridge.org/core/journals/…
8/ Addition of air cleaners like portable HEPA filters are an important part of keeping indoor air clean from infectious respiratory aerosols and all manner of suspended particles (like wildfire smoke, cooking aerosol, urban pollution PM).
9/ HEPA filters have been championed by indoor air experts as a key part of the strategy to offer in-person learning in the Fall and beyond. See this thread on an excellent example by NYC schools, with further comment & resources on filtration in schools.
10/ And if you like how well portable #HEPA filters work - just think of the tremendous benefit by adding to every school classroom in the US like @CorsIAQ & @j_g_allen have been saying for over a year.
Cost analysis from February:
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