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DrEricDing's profile
Eric Feigl-Ding
Eric Feigl-Ding
Eric Feigl-Ding
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@DrEricDing

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Eric Feigl-DingVerified account

@DrEricDing

Epidemiologist & health economist. Senior Fellow @FAScientists. Former 16 years @Harvard. @JohnsHopkins alum. COVID updates since Jan '20: http://nym.ag/3olszuo 

Washington DC & Virginia
fas.org/expert/eric-fe…
Joined January 2009

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    1. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

      This bothers me so much— 📍There are still no official CDC guidelines for ventilation for schools—no rules on adequate air exchanges—despite so much science on >=5 ACH/hour. 📍And 6 feet is not safe for airborne virus, says ex-OSHA chief. #COVID19 🧵 https://www.nj.com/opinion/2021/02/former-osha-head-were-getting-it-wrong-on-covid-workplace-safety.html …pic.twitter.com/JEwMZGv5oC

      182 replies 1,723 retweets 3,859 likes
      Show this thread
    2. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

      2) “We’ve known for nearly a year that COVID is airborne – yet aside from hospitals, few workplaces acknowledge that the virus can hang in the air. Instead, they emphasize surface-scrubbing and physical distancing”

      23 replies 315 retweets 955 likes
      Show this thread
      Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

      3) We need at 5 or more air exchanges per hour says @HarvardChanSPH researchers, either via natural ventilation or air cleaning.pic.twitter.com/juxZcNDaRe

      8:04 PM - 22 Feb 2021
      • 206 Retweets
      • 542 Likes
      • Ostara Fay 👑 Duck and Cover Frankenvanni SarahA Devin Nunes' Cabrito Jeffrey Martin Hayley Brown AK2=theAquisitionKnowledge2=GrandNegasAKarriemKhan Paulo M Espinosa
      8 replies 206 retweets 542 likes
        1. New conversation
        2. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          Eric Feigl-Ding Retweeted Eric Feigl-Ding

          4) And air disinfection such as with HEPA filters do work. New study this past month demonstrates it for the coronavirus. Reduced inhaled dose by 6x on optimal 5.7 ACH setting. Good thread 🧵 summary below.https://twitter.com/DrEricDing/status/1363638390432948227 …

          Eric Feigl-Ding added,

          Eric Feigl-DingVerified account @DrEricDing
          AIR DISINFECTION—To reduce airborne #SARSCoV2 risk, new study finds HEPA cleaners, with total air exchange rate of 5.7  ACH/hour, after 2 hours in closed room with a highly infective person—the inhaled dose is 6x reduced! ➡️We need these for schools.🧵 https://www.tandfonline.com/doi/full/10.1080/02786826.2021.1877257 … pic.twitter.com/wkckfQ5CU3
          Show this thread
          9 replies 121 retweets 382 likes
          Show this thread
        3. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          5) To understand air cleaning and not be tricked by snack oil disinfection machines, you have to understand the CADR value... The key to portable air cleaners is what is called a clean air delivery rate (CADR).

          3 replies 61 retweets 207 likes
          Show this thread
        4. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          6) The CADR is the product of two numbers: CADR = f x Q.  f is the fraction removal efficiency of particles that go into the system. Q is the volumetric flow rate in cubic feet per min. If 100 particles go in & 70 are removed, then f = 0.7. HEPA has basically 0.999+, or ~1.0.

          1 reply 53 retweets 169 likes
          Show this thread
        5. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          7) warning—some shady manufacturers who claim that their devices are nearly 100% efficient (f ~ 1.0)—sounds great.  But what they do not tell you is that the flow rate of air through the device (Q) is very low.  So, f x Q is low—many devices that are quiet, e.g., ion generators.

          1 reply 60 retweets 174 likes
          Show this thread
        6. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          8) CADR ➡️ ACH conversion: Eq ACH = CADR x 60/(A x Z) CADR = clean air delivery rate in cubic feet per minute A = floor area in square feet Z = ceiling height in feet The number 60 is to convert the CADR to cubic feet per hour Eq ACH = air changes per hour.

          4 replies 45 retweets 172 likes
          Show this thread
        7. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          9) Basically if you know the air cleaning device’s CADR, and you know the room size (volume), then you can calculate ACH that the cleaner adds. If your room has 2 ACH via natural ventilation, and your HEPA filter has +3 EqACH via above formula, then your room’s total ACH = 5!

          2 replies 57 retweets 168 likes
          Show this thread
        8. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          10) The organization that certifies air cleaners for manufacturers who want certification.  It is the Association of Home Appliance Manufacturers (AHAM) - https://www.aham.org/  They have a standard test with smoke, dust and pollen to determine CADR for each.pic.twitter.com/CXznYbwR25

          5 replies 69 retweets 214 likes
          Show this thread
        9. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          Eric Feigl-Ding Retweeted Eric Feigl-Ding

          11) I want declare I have no financial relationship with any HEPA filter maker. Also really cool is this low cost MERV13 homemade device called “Corsi Box”. This fan’s air speed is 580 feet/min—so multiply by the area of the fan—to get Q. The F of these filters is 0.9 I’m told.https://twitter.com/DrEricDing/status/1362895328459059200 …

          Eric Feigl-Ding added,

          Eric Feigl-DingVerified account @DrEricDing
          20) “So how did “Corsi Box Fan with 5 MERV 13 Filters” Air Cleaner perform? Great. Airflow from the fan was 580 feet per minute. Box ensures more surface area of the filter media – better air flow with minimal strain on the fan motor. Plus the filters will last for 6 months” pic.twitter.com/NzsEGPOH6E
          Show this thread
          7 replies 72 retweets 245 likes
          Show this thread
        10. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          12) Now to be fair, the CDC does put out general suggestion on ventilation and air cleaning in buildings for COVID risk. And says HEPA and UV work for Covid. But they don’t set specific guidelines on classrooms meeting 5 ACH per hour. That’s the issue. https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation.html …pic.twitter.com/V1zKQHSQhR

          3 replies 57 retweets 187 likes
          Show this thread
        11. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          13) one of my favorite videos— VENTILATION is key. Both ventilation and masks needed to reduce risk indoors. But most buildings & classrooms not ventilated well enough. Hence need for air cleaners like portable HEPA filters.pic.twitter.com/qhz8cs0grH

          Eric Feigl-Ding
          7 replies 167 retweets 339 likes
          Show this thread
        12. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          14) I want to add, CDC doesn’t need to bless any specific machines or filters. That’s not their job. They need to just set standards on adequate ACH for workplaces and schools, and maybe minimum CADR for devices — some bad devices have CADR of 20-30, while good HEPA have 250-300.

          4 replies 54 retweets 196 likes
          Show this thread
        13. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          15) So if total ACH we should aim for is 5+ from natural ventilation + air cleaning, then what is the typical ventilation ACH in classrooms? Well, it’s rarely ever 4. @CorsIAQ says the median he’s seen is 2, while Arlington VA schools it’s 2.4, but as low as 0.5 in some classes!

          4 replies 39 retweets 107 likes
          Show this thread
        14. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          16) How important is ventilation outside of COVID risk? “There is compelling evidence, from both cross‐sectional and intervention studies, of an association of increased student performance with increased ventilation rates.”...https://onlinelibrary.wiley.com/doi/abs/10.1111/ina.12403 …

          2 replies 46 retweets 135 likes
          Show this thread
        15. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          17) “There is evidence that reduced respiratory health effects and reduced student absence are associated with increased ventilation rates.”

          1 reply 35 retweets 133 likes
          Show this thread
        16. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          18) “The net annual costs, ranging from a few dollars to about 10 dollars per person, are less than 0.1% of typical public spending on elementary and secondary education in US. Such expenditures seem like a small price to pay given the evidence of health & performance benefits.”

          3 replies 36 retweets 132 likes
          Show this thread
        17. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          19) Here is the cost breakdown of one good portable HEP filter per standard classroom, done by @CorsIAQ. The total cost across 3 years is just $11/student. That is nothing compared to the cost of other school materials. And this improves learning! We need to do this.pic.twitter.com/BrZFV8zB09

          8 replies 69 retweets 193 likes
          Show this thread
        18. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          20) The good news is that $130 billion designated for schools is coming in the Democrat proposed bills! And it will offer funding for ventilation. But will it be prioritized? I’m working on a push for this on behalf of safe reopening. I will announce tomorrow.pic.twitter.com/ZYBJo7OlgW

          6 replies 54 retweets 196 likes
          Show this thread
        19. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          21) I want to add that while HEPA cleaners are well-suited for rooms under 1,000 square feet, with ceiling heights of 8-10 feet—they are not sufficient for larger rooms like big cafeterias, gymnasiums, auditoriums, indoor swimming pools. For these, you then need “Upper Room UV”pic.twitter.com/hITrNSsefL

          7 replies 49 retweets 152 likes
          Show this thread
        20. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          22) Upper-room UV fixtures are mounted on ceilings and are safe for humans because they do not expose UV to students and teachers. They draw air upward, then disinfect the air above people who are in the room, adding a high number of clean air exchanges to a room’s air supply.

          4 replies 47 retweets 140 likes
          Show this thread
        21. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          23) Upper-Room Ultraviolet devices can sometimes achieve 15 or more air exchanges per hour if done well. Some UV devices can also avoid specific wavelengths that cause ozone, allowing it to be further safe.

          4 replies 54 retweets 158 likes
          Show this thread
        22. Eric Feigl-Ding‏Verified account @DrEricDing 22 Feb 2021

          Eric Feigl-Ding Retweeted Eric Feigl-Ding

          24) Bottomline: there are MANY ways to achieve 5 or more air exchanges per hour. Natural ventilation + also via air disinfection approaches. Some don’t want to chase 5 ACH per hour, but I say $11/year per child is definitely worth it—& there is funding coming soon. See this 🧵https://twitter.com/DrEricDing/status/1362880620343484416 …

          Eric Feigl-Ding added,

          Eric Feigl-DingVerified account @DrEricDing
          📍Pardon my vent about insufficient ventilation / air exchange & school policy. Air exchange (via fresh air or disinfection) is really important for reducing #COVID19 transmission—we should aim for 5-6 air exchanges per hour. Achieving 5-6 is harder, but should we give up? No!🧵 pic.twitter.com/OTSTv4MoG6
          Show this thread
          8 replies 69 retweets 195 likes
          Show this thread
        23. Eric Feigl-Ding‏Verified account @DrEricDing 23 Feb 2021

          25) Ventilation with new air is best. Here is how to ventilate your school classrooms if unable to open window. #COVID19pic.twitter.com/ZiOdMG2GPs

          NHK WORLD News
          COVID-19: Clearing the Air Effectively
          6 replies 114 retweets 223 likes
          Show this thread
        24. Eric Feigl-Ding‏Verified account @DrEricDing 23 Feb 2021

          26) let’s learn some lessons from 100+ years ago in the last great global pandemic... doctors and nurses kept all windows open. Fresh air ventilation was the key to defeating the pandemic. If only we can heed these lesson now. Great piece by @sarahzhang.https://www.theatlantic.com/health/archive/2021/02/bad-air/618106/ …

          13 replies 175 retweets 432 likes
          Show this thread
        25. Eric Feigl-Ding‏Verified account @DrEricDing 23 Feb 2021

          Eric Feigl-Ding Retweeted Eric Feigl-Ding

          27) CDC needs to emphasize school ventilation. This is something all airborne virus experts agree on. Masks, ventilation / air cleaning, and rapid testing. Vaccination is good if available, but air cleaning is much easier and faster to solve if we have Biden Covid bill fundinghttps://twitter.com/DrEricDing/status/1360343218177646597 …

          Eric Feigl-Ding added,

          Eric Feigl-DingVerified account @DrEricDing
          What is missing from this CDC school reopening priority list? Airborne virus guidance! Like almost nothing in 33 page document on ventilation except 1 paragraph on open the windows, but only if feasible. Ventilation should be #2 behind masks! #COVID19 https://www.cdc.gov/coronavirus/2019-ncov/downloads/community/schools-childcare/K-12-Operational-Strategy-2021-2-12.pdf … pic.twitter.com/WA2T2yDkVN
          Show this thread
          10 replies 63 retweets 133 likes
          Show this thread
        26. End of conversation

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