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.🧵…
2) In times when classes were conducted with windows and door closed, the aerosol concentration was reduced by more than 90% within less than 30 minutes when running the purifiers (air exchange rate 5.5 /hour)—and decreased by more than 95% within 37 minutes.
3) A **halving of the particle concentration was reached in 10.0, 7.0 or 5.4 minutes** (green, black and red lines, respectively), depending on the total flow of the purifiers.

The blue line shows a typical slow decrease when no purifiers were used.
4) Bottomline: Air disinfection cleaners can “reduce the aerosol load in a classroom in a fast, efficient and homogeneous way.”

(I have no relationships with any HEPA filter company)
5) “In situations when windows and doors are closed for a longer period of time a large reduction in the inhaled dose of particles containing virus RNA is achieved and therefore the risk of aerosol infection is likely to be lowered”
6) That said, ventilation is most key. VENTILATION is key. Both ventilation and masks needed to reduce risk indoors. But most buildings not ventilated well enough. Hence need for air cleaners like portable HEPA filters.

7) The good news is that there is $130 billion designated for schools in the Democratic proposed bills! And it will offer funding for ventilation. But will it be prioritized? I’m trying to work on this on behalf of schools. Will keep you all posted on the progress.
8) Meantime, there is another alternative poor-man’s Jerry rigged solution with a box fan + 4 or 5 MERV13 air filters... to create a “Corsi Box”!!! And it works great according to experts if you can keep it together well.
9) Ideally, we want 5-6 air exchanges (ACH) per hour, via combination of air cleaning + natural ventilation. But many school classrooms have natural ACH of just 0.5 per hour... average was 2-2.5 for school classrooms sampled / assessed in Arlington, Virginia (personal comm).
10) Sadly, ventilation guidance in the CDC school reopening report was buried. It does exists but very weakly in the technical details.
11) That said, the CDC does give indoor air guidance for #COVID19 and recognizes ventilation, HEPA filters, and germicidal UV light (that avoid ozone).…
12) Meanwhile, the EPA also give indoor air cleaning guidance. Depending on room size you should get a HEPA filter with certain minimum CADR (Clean air delivery rate) needed for your room. Go with 300 CADR level HEPA filter to be safe for most rooms.…
13) If you’re technical, there is calculator for what you need based on room size, ceiling height and ventilation situation. The higher the CADR, the more air changes per hour. Your goal is minimum three to five total air changes per hour. But 6 is ideal.…
14) Besides #COVID19 risk, there’s also small studies that show low ventilation rates in elementary schools correlate with low math scores.
15) To be clear, natural ventilation still best. Here is how to ventilate your school classrooms if unable to open window. #COVID19
16) Air disinfection for classrooms with portable HEPA is also very affordable— cost is just <$10 per student to start and only $11/student for 3 years, according to @CorsIAQ. Much less than cost of most school books.
17) The DIY Corsi Box (also called by some as the Comparetto Cube) as a low cost way to filter the air, is also a good kids learning activity.

Though nota bene—don’t touch the sides of the filter after it starts running. Virus particles can stick to it.…
18) We need CDC and OSHA standards for safe school & workplace ventilation and air cleaning guidelines!!! See my detailed 🧵 of what we need for safe schools!

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Eric Feigl-Ding

Eric Feigl-Ding Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @DrEricDing

23 Feb
TRIPLE WORRISOME—Data says the new variant that is now dominant strain in California:

📌spreads FASTER

📌evades antibodies from #COVID19 vaccines or prior infection

📌causes more severe illness.

➡️Scientist says “the devil is here” #B1427 / #B1429🧵… Image
2) “In a study that helps explain the state’s dramatic surge in COVID-19 cases and deaths — and portends further trouble ahead — scientists at UCSF said the mutations that characterizes the homegrown CA should mark it as a “variant of concern” on par with those from 🇬🇧 , 🇿🇦 & 🇧🇷”
3) “The devil is already here,” said Dr. Charles Chiu, who led UCSF team of geneticists, epidemiologists, statisticians and other scientists in a wide-ranging analysis of the new variant, which they call B.1.427/B.1.429. “I wish it were different. But the science is the science.”
Read 19 tweets
23 Feb
STEALING VACCINE SLOTS FROM MINORITY COMMUNITIES—A CA program intended to improve #COVID19 vaccine access to people in hard-hit communities of color is being misused by affluent using codes to steal appointments reserved for underserved residents. 🧵… Image
2) “The program to address inequities in vaccine distribution relies on special access codes that enable people to make appointments on My Turn vaccine scheduling website. The codes are provided to community organizations to distribute in largely Black and Latino communities.”
3) “But those codes have also been circulating, in group texts and messages, among the wealthier, work-from-home set in Los Angeles, The Times has learned. Many of those people are not yet eligible for the vaccine under state rules.”
Read 6 tweets
23 Feb
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 🧵… Image
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”
3) We need at 5 or more air exchanges per hour says @HarvardChanSPH researchers, either via natural ventilation or air cleaning. Image
Read 27 tweets
22 Feb
I think Texas needs new leaders... First Ted Cruz and now...

Texas’s Attorney General Ken Paxton and wife TX Senator Angela Paxton both fled to Utah during #TexasBlackout to avoid the freezing cold and water outage while their voters suffered.…
2) Texas’s elected leaders directly control @ERCOT_ISO — and the deregulation and lack of safety investments that led to Texas’s electricity ⚡️ crisis and humanitarian crisis.
3) The breathtaking callousness of Texas leaders is quite something to behold. It is bottomless.
Read 7 tweets
22 Feb
When I promised all of you Biden listens to scientists, I meant it. 👇
2) Like I said... promises made, promises kept....

Our TV 📺 ad months ago...
3) In contrast to [he who shall not be named] and ignored warnings of doctors and us epidemiologists...
Read 4 tweets
22 Feb
📍OUTBREAK OF #B117 AT SEVEN SCHOOLS—sudden outbreak of #COVID19 cases at a British Columbia 🇨🇦—all elementary and middle schools. Genetic sequencing shows #b117 in early cases linked to outbreak. Classes quarantined. All the schools still remain open. 🧵…
2) British Columbia 🇨🇦 teachers are now incredibly worried by the latest sudden 7 school outbreaks, and demanding decisive actions.
3) British Columbia is having a major increase in transmission — and has the highest R in Canada 🇨🇦 currently.
Read 20 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!