1/ Distancing and Shared Air.

Full disclosure. I want children back in school for their mental, social, & physical health, & for their future.

But I continue to be deeply concerned by a lack of attention & messaging on what needs to be done to EFFECTIVELY make schools safer.
2/ IMO, 3 ft of physical distancing is probably fine with UNIVERSAL MASK WEARING in classrooms in terms of inhalation dose by close contact.
3/ I have some concern about such distancing when masks are NOT worn, e.g., while eating, particularly given a much more infectious virus now than "coronavirus classic". I provided some guidance on lunch periods in my EPA school webinar months ago - at corsiaq.com
4/ My greater concern w/ 3 ft distancing is that it leads to potential for higher occupancy of classrooms. This is good for getting kids back in school, but remains a significant concern if we miss the need to EFFECTIVELY address shared air.
5/ A 6 ft radius in most classrooms yields between 30 to 40% of normal occupancy, depending on classroom configuration. It is easy to see how 3 ft will lead to doubling or more of occupancy.
6/ 2 x occupancy means a doubling of the probability of an infected student in the space, or conversely 2 x the number of infected students in a school. Since masks do not capture all emissions, this means higher levels of virus-laden particles in shared air.
7/ What this means is that with less distancing MUCH MORE attention needs to be given to EFFECTIVELY reducing virus-laden particle concentrations in the far field (shared air). This message is NOT being appropriately conveyed to the public or school districts.
8/ Greater occupancy should mean even higher ventilation rates coupled with some combination of improved filtration for the fraction of air recirculated, use of portable HEPA filtration systems, & consideration of UVGI (upper-room or in mechanical system [if recirculation used]).
9/ Again, I want children back in school for their social, physical, & mental health. Have agreed w/ @j_g_allen and others on that point since last summer. But we all stressed the need for greater ventilation & PROVEN engineering controls before re-opening.
10/ Our message was not received then. Our nation fumbled the football. And we are fumbling again as school districts across the US are not getting the message pounded into them that this is an airborne infectious disease and that far-field (shared air) inhalation dose matters.
11/ And many of those who seem to be getting the general message are WASTING precious financial resources on unproven, highly ineffective, and in some cases detrimental technologies. They are hearing from salespeople and not experts who know what is effective vs. not.
12/ The lack of consistent (or any) messaging by central authorities on the importance of shared air beyond close contact, and how to EFFECTIVELY lower inhalation dose in indoor spaces, has been an unfortunate failure during this pandemic.
13/ And that lack of effective messaging is now leading to woefully unfortunate decisions by school districts across North America. Get kids back in school - yes. Do it wrong - NO. Let's do it right.

• • •

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

Keep Current with Dr. Richard Corsi

Dr. Richard Corsi 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 @CorsIAQ

20 Mar
1/ As states struggle w/ funding higher education they should not look at this as allocation, but rather investment in both the short & long-term future. Investment in STEM education has a rapid and significant return on investment when students stay in-state after graduation.
2/ I've done a detailed analysis based on graduates of the Maseeh College of Engineering and Computer Science @Portland_State. Every $1 spent on a student yields a return on investment of 12%/yr ($320% over 10 yrs) in Oregon State income tax alone.
3/ This analysis is based on fraction of graduates employed in Oregon, starting salaries w/ annual increases, and use of the State's income tax calculator. The ROI would be much higher if property tax, start-up businesses, etc., are included.
Read 4 tweets
17 Mar
1/ I have spoken with dozens and dozens of school districts. My recommendations include universal masks, increased ventilation, and stick with PROVEN technologies.
2/ Improved filtration as per MERV rating (to MERV-13 if possible), portable HEPA filtration (appropriately-sized), and upper-room or in-mechanical-system UVGI (in-system if significant recirculation rates high). Add good DYI box-and-fan systems if sealed properly. Just Do It!
3/ When a district official says "Yes, but I hear that this ..." or "What about this ....". I just repeat - stick with PROVEN technologies (see above). "But we were told ..." stick with PROVEN technologies. "But ...." Stick with PROVEN technologies.
Read 7 tweets
14 Mar
1/ Concerns about under-ventilation of indoor spaces are FAR from new. Here are just 3 of many examples.
2/ Ben Franklin (18th century): "I am persuaded that no common Air from without, is so unwholesome as the Air within a close Room, that has been often breath'd and not changed" Franklin advocated exposure to fresh air & including open windows when sleeping.
3/ Florence Nightingale (mid 19th century): “Keep the air the patient breathes as pure as the external air, without chilling him.”
Read 6 tweets
12 Mar
1/ Proven Technology. The cost to put a very good portable HEPA filtration system in a classroom that typically holds 24 or 25 students is approx $10/student/yr (year 1), with recurring filter & energy costs of around $7/student/yr. Per year. Not per day, week, or month.
2/ The system can often yield an equivalent of 3 or more ACH &, at ventilation rates I have seen in a majority of schools in Texas, 60-75% overall reduction in inhaled dose of virus-laden paricles in shared air.
3/ In the US we spend approximately $15,000/year to educate a SINGLE student. To effectively reduce virus-laden particles in classroom air would add a whopping $7-10/student each year to this total. Two Grande Frappaccunios, folks. Proven technology.
Read 4 tweets
11 Mar
1/ Proven and unproven technologies. We have proven technologies for removing virus-laden aerosol particles from air: Increased ventilation, portable HEPA filtration systems (properly sized for space), and advanced MERV-rated filters (12 or 13) if mechanical system can handle.
2/ We have a proven technology that will inactivate viruses in aerosol particles - upper-room UVGI.
3/ These technologies have been proven for many decades, studied by many independent researchers for their effectiveness and published in peer-reviewed journals (which means even more analysis by independent researchers).
Read 9 tweets
8 Mar
1/ Recently spoke with an official for a private multi-school organization that has large garage-door-like openings on every classroom. I was asked about ventilation with what amounts to nearly an entire wall open to the outdoors.
2/ This is similar to research that @JohnnyGrinch & I did a few years ago on ozone decay rates in residential garages in Austin. This work required simultaneous analysis of air changes per hour in garages (abstract only here)
3/ In 12 garages @JohnnyGrinch measured a mean of approximately 0.5 ACH in garages w/ doors closed (range from close to 0 to 0.8/hr. A limited amount of experiments were done with the door completely open.
Read 10 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!