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j_g_allen's profile
Joseph Allen
Joseph Allen
Joseph Allen
@j_g_allen

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Joseph Allen

@j_g_allen

Assoc Prof @HarvardChanSPH; Lancet @CommissionCOVID (Chair Task Force on Safe Work/School/Travel); Coauthor of HEALTHY BUILDINGS @Harvard_Press; WaPo, NYT, HBR

Boston
hsph.harvard.edu/joseph-allen/
Joined October 2011

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    Joseph Allen‏ @j_g_allen 16 Apr 2021

    In this new piece in @JAMA_current, I teamed up w/ colleague @AndrewMIbrahim to argue that 1) evidence for airborne spread is strong 2) enhanced ventilation/filtration is needed 3) 4-6 air changes per hour should be target for small volume spaces THREADhttps://jamanetwork.com/journals/jama/fullarticle/2779062 …

    8:03 AM - 16 Apr 2021
    • 99 Retweets
    • 164 Likes
    • Konstantia Papadaki Comunidad @AIREyVIDA2021 marc k9icu Adria Dre Claudia Doris Gratzke Jeanne Bayaca meridianfire SD🐝💙💜🤍💚🪓
    7 replies 99 retweets 164 likes
      1. New conversation
      2. Joseph Allen‏ @j_g_allen 16 Apr 2021

        An important flaw exists in how buildings operate. Current ventilation standards are bare minimums not designed for infection control. Several orgs have called for higher ventilation, but no targets set.

        1 reply 6 retweets 20 likes
        Show this thread
      3. Joseph Allen‏ @j_g_allen 16 Apr 2021

        Can’t really go to a school, university, office and just say ‘bring in more air’. Next question is always, “ok, but how much?” That’s what we tried to address with this commentary.

        1 reply 4 retweets 20 likes
        Show this thread
      4. Joseph Allen‏ @j_g_allen 16 Apr 2021

        The case for higher ventilation/filtration is straightforward: 1) majority of aerosols emitted are small (<10um), stay aloft for a long time, and travel beyond 6 feet 2) many well-described outbreaks indoors, no masks, low/no ventilation, even with physical distancing

        1 reply 4 retweets 16 likes
        Show this thread
      5. Joseph Allen‏ @j_g_allen 16 Apr 2021

        3) basic principles of exposure science and inhalation dose risk reduction (lower intensity exposure = lower risk) 4) 4-6 ACH is consistent with what healthcare settings use

        1 reply 2 retweets 15 likes
        Show this thread
      6. Joseph Allen‏ @j_g_allen 16 Apr 2021

        5) historical evidence shows ventilation plays key role in mitigating disease spread (measles, TB, influenza, SARS-CoV-1...)

        1 reply 3 retweets 16 likes
        Show this thread
      7. Joseph Allen‏ @j_g_allen 16 Apr 2021

        This call for higher ventilation is (finally!) supported by Fauci/NIAID and CDC. Has also been supported by ASHRAE. One problem – when orgs have said ‘higher ventilation’, they failed to set a target! (Whoops!)

        2 replies 4 retweets 20 likes
        Show this thread
      8. Joseph Allen‏ @j_g_allen 16 Apr 2021

        We argue for 4-6 effective air changes per hour. The ‘effective’ part is key because typically ACH means ‘outdoor air changes’. Here we just want ‘clean’ air, either from outdoors or through highly filtered air. (‘clean’ here refers to virus-free, not ‘clean’ in absolute sense…)

        1 reply 5 retweets 17 likes
        Show this thread
      9. Joseph Allen‏ @j_g_allen 16 Apr 2021

        The 4-6 total air changes of clean air is what hospitals use in lower-risk areas of the hospital. But, if you take a look at the table we provide in the supplement, most other places you spend time don’t come close to this. Schools? ~3 ACH Homes? ~0.5 ACH Stores? ~1.7 ACH

        1 reply 5 retweets 15 likes
        Show this thread
      10. Joseph Allen‏ @j_g_allen 16 Apr 2021

        Last, bringing in more outdoor air / using better filters isn’t without challenges/caveats: 1) more outdoor air = more energy. Need energy-efficient systems 2) ventilation/filtration only address far-field airborne, not near-field

        1 reply 4 retweets 16 likes
        Show this thread
      11. Joseph Allen‏ @j_g_allen 16 Apr 2021

        3) ACH approach not the best for large volume spaces (gyms, atria) 4) ACH v. volumetric flow (eg, cfm/p + cfm/sqft) both valid. ACH ensures minimums, even for under-occupied space. cfm/p approach scales up if have high densitites.

        1 reply 3 retweets 11 likes
        Show this thread
      12. Joseph Allen‏ @j_g_allen 16 Apr 2021

        5) 4-6 ACH may not be enough for higher risk locations, and for places where masks are not being used 6) There are many other benefits to more outdoor air beyond infection control (reduced absenteeism, better cognitive function, fewer ‘sick building’ symptoms…).

        1 reply 4 retweets 13 likes
        Show this thread
      13. Joseph Allen‏ @j_g_allen 16 Apr 2021

        I also want to thank @ShellyMBoulder and @cedenolaurent for early convos on ACH for schools. We built a simple tool over weekend in July to help schools pick portable air cleaner. But again, there were no targets set by any authoritative body. So we added this chart to the toolpic.twitter.com/i0E9kS2fGN

        2 replies 15 retweets 47 likes
        Show this thread
      14. Joseph Allen‏ @j_g_allen 16 Apr 2021

        Big picture. The way we design/operate our buildings has a big impact on our health, including infectious disease. The reality is our ventilation design standards are bare minimums not designed for infection control, or health promotion. That needs to change. #HealthyBuildings

        0 replies 7 retweets 34 likes
        Show this thread
      15. End of conversation

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