B117 is spreading in US but we have not seen the explosion yet. Brace yourselves. These outcomes in Italy & Israel should give pause, a motivation for tripling down on reducing inhalation dose in all activities, and a quintupling down on layered dose reduction in schools. more..
Dose and risk reduction in schools must include re-opening plans based on extent of community spread, rapid exit plans, rapid testing if possible, rigorous and universal mask requirements, distancing and lower occupant density, pod groups, increased ventilation ....
supplemented with single zone filtration, e.g., portable HEPA air cleaner, to achieve at least 6 effective air changes per hour, as much outdoor activity (including teaching) as possible (I used to teach lectures on occasion outdoors in Texas - it can be done when elements allow)
Add significantly enhanced filtration as possible when recirculation is necessary (to MERV13 if possible, but MERV12 and 11 are still much better than MERV8). Consider upper-room UVGI. Don't fall for unproven technologies or gimmicks.
Make ample use of time. Outdoor mask breaks for 20 minutes three times per school day while continuing to ventilate and filter in an empty classroom can dramatically reduce virus-laden aerosol particles in air prior to return and significantly reduce integrated school day dose.
Come on school districts. Be smart in the process. Just do it, right!

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More from @CorsIAQ

6 Feb
1/ Clean Air Delivery Rate (CADR). The CADR of a portable filtration system is:

CADR = f x Q.

f is the fractional removal efficiency of particles that pass through a device (value = 0 to 1). Q is the volumetric flow rate of air through the device (e.g., m3/hr, ft3/min). ...
2/ A portable air cleaner may be highly efficient (high value of f) but also highly ineffective at removing particles from air if Q is very small. This is the case for a wide range of ion generators. Don't be fooled by claims of high efficiency. It's f x Q that matters.
3/ On the other hand, a portable filtration system might have a lower efficiency (say, 0.5) but a very high air flow rate that leads to significant reduction of particle concentrations in air. It is f x Q that matters.
Read 19 tweets
3 Feb
1/ SCHOOLS. A few days ago I watched the Director of the National Economic Council say we need children back in school so parents can get back to work. While that is one benefit, it should not be construed as the sole or even primary reason for wanting children back in school.
2/ The school environment is important for the mental, social, and in some cases physical growth of children. Remote learning has also led to an extraordinarily high virtual drop-out rate in many cities.
3/ But whether for schools that are already open or those that will be re-opened, we ought to invest in infrastructure that makes them substantially safer during this pandemic and healthier beyond the pandemic. It is not rocket science. Just do it!
Read 21 tweets
31 Jan
1/ It takes a lot to move higher education, but COVID-19 is doing it. Many in higher ed are looking at a much different future, certainly much more on-line education (that's been happening and will accelerate).
2/ Expect more in-person (face-to-face) lectures w/ simultaneous live-streaming and recording to provide students w/ options, less demand for on-campus housing and transportation services at many universities, universities providing greater IT support off campus, and more.
3/ There is potential for greater service to under-served communities and advancement in diversity, equity and inclusion with these changes. But there is also a risk of doing it wrong and a loss of sense of academic community and support.
Read 9 tweets
27 Jan
1/ I am seeing many interpreting this as "it's safe to send kids back to school." That's a misinterpretation. First, safe implies certainty, which is not true here. What can be said is that it is much safer to re-open schools if specific risk reduction measures are taken.
2/ Densely-populated, poorly-ventilated (the majority of schools I have studied in Texas) schools, especially during any periods when masks are not worn are a recipe for infection. Ask Israel.
3/ Proper layered risk reduction works, is not rocket science, and does not have to break the bank. More on LRRS in my webinar here:
Read 6 tweets
23 Jan
We are a couple of weeks away from the anniversary of the first known COVID-19 death in the US. In February 2020 the US had approximately 20 total deaths. As we move into February 2021 we will be pushing 500,000 deaths w/ a trajectory aimed much higher.
We failed a year ago. Infections got too far ahead of us. Our response should now be an all-out war to starve this virus & its new variants of hosts, to do what we should have done 10-11 mos ago. We can lower the future death total before vaccines get us to where we need to be.
The ABSOLUTE MINIMUM that must be done to reduce inhalation dose in both the near- and far-fields is (1) UNIVERSAL mask wearing in ALL indoor environments other than one's own home in the presence of immediate family, and (2) physical distancing of AT LEAST six feet.
Read 6 tweets
21 Jan
I agree w/ @linseymarr that lower than 800 ppm is often needed, but we also need recognition that what is a "safe" CO2 concentration in on environment may not be safe at all in another, and vice-versa.
The actual max acceptable value depends on # of people present, typical time spent in environment, mask requirements, respiratory minute volume, and effectiveness of controls.
For 25 people spending 2 hrs in the same indoor space, a rough estimate based on a quanta generation rate similar to that in Restaurant X is CO2 < 695 ppm for an infection probability of < 5% w/o masks or controls. Assuming worst (no masks or controls) provides a safety factor.
Read 7 tweets

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