Thread by @CorsIAQ

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.