Our new office policy we're finalizing essentially takes this viewpoint. In 3 of our offices, we've assessed high vaxx rates combined w/ addressing the Delta far field risk via ventilation/filtration is adequate enough for vaxxed employees (almost 100%) to go sans masks. 1/
Even in metro areas currently deemed by the CDC as having high or substantial community transmission.

To have vaxxed employees go sans masks in our other 2 offices, relative to their current lower office vaxx rates, the Delta far field risk needs to be addressed through... 2/
some combination of additional ventilation/filtration improvements, increasing vaxx rates, setting lower occupancy limits, or having non-vaxxed employees WFH - we are still assessing the best path forward for each of those locations.

We estimated the far field risk for... 3/
each office location using our Facility Infection Risk Estimator (branchpattern.com/research/facil…), taking office vaxx rates into account & assuming 1 infected individual is present. We also assessed our eACH for each office.

For the near field risk, we are able to locate seats a... 4/
minimum of 3' apart (greater in many cases). Though we recognize depending on airflow patterns 3' isn't necessarily adequate in some cases. We will be asking vaxxed employees to mask up in situations where they have to be in close proximity (< 3') to others for more than a... 5/
brief encounter, such as during a meeting. For the 3' - 6'ish range, it will likely be up to employees to decide if they want to wear a mask.

Once our metro rates fall w/in the moderate community transmission range, we will likely drop the near field masking requirement. 6/
But as @j_g_allen points out, this near field masking requirement may be over conservative relative to the actual risk that an infected employee, who is also shedding a lot of virus, is in the office on any given day, & that another vaxxed employee then becomes infected. 7/
As a thought exercise, I'll take the KC metro area where one of our offices resides. Let's assume actual community transmission falls somewhere between cases/100,000 & % positivity rate (though likely much closer to the former). Using CDC tracking data from 10/4, I'll... 8/
arbitrarily assign a weighting of 0.825 to the cases/100,000 & 0.175 to the % positivity rate. I'll use the resulting weighted average as an estimate of the community transmission rate and determine this for 8 counties in the metro area. I'll then average those 8 values,... 9/
weighted by each county's population. This gives me a value of 1.59% as the KC metro area's estimated average transmission rate on 10/4. The KC office has 30 employees, so if everyone is there, the probability that 1 employee is infected is 38.2% using this 1.59% estimate... 10/
of community transmission.

BUT this assumes our employees are a representative sample of the KC metro area population. They aren't, because we're almost 100% vaxxed compared to the roughly 45% - 65% fully vaccinated rates, depending on the county. 11/
In addition, our employees generally aren't in situations that potentially expose them to infected individuals as much as some other demographic groups in the metro area. And just because an infected person is present doesn't mean they are at their most infectious stage. 12/
These & other factors mean that the 38.2% over-estimates the likelihood of an highly infectious employee being present in the office on any given day. Maybe it's under 15%. Maybe even under 5%. And that's w/ community transmission deemed by the CDC as High. 13/
So our near field risk masking measures may be conservative, but I think even if the risk is just 5%, we'll continue w/ them until community rates drop lower. Certainly at 15% we would want to keep them. We don't want to be a link in a chain of community transmission. 14/
However, I generally feel confident going sans masks otherwise in these 3 offices that have addressed the far field risks via ventilation/filtration & vaccinations.

But it's important to note that we are able to go sans mask in our work environment, w/ current community... 15/
transmission rates what they are, because of privilege. 16/

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More from @MarcelHarmon1

8 Oct
"'We were in no way expecting what happened,' says Superintendent Adam Hatfield." @TheKLC

Expression of every aerosol scientist, engineer, etc., who've been promoting #COVIDisAirborne strategies since spring 2020: media.giphy.com/media/A928XcII…. #ksed #ksleg 1/

klcjournal.com/covid-19-schoo…
W/ the #DeltaVariant we knew districts would be taking larger risks than necessary if all relevant mitigation strategies weren't implemented - . That we haven't had more districts close for a period of time is pretty fortunate considering everything. 2/
That we're still arguing over the basics of how to respond to a pandemic driven by a predominantly airborne virus demonstrates a multi-level failure of public health & government, exacerbated by a history of underfunding public health, public education, current levels of... 3/
Read 4 tweets
6 Oct
A few questions for the UV specialists. 1st, are the studies/modeling that have been done so far relative to Far UVC impacts on eyes/skin sufficient to answer questions regarding a) potential negative impacts from chronic (continuous or repeated) exposure,... 1/
b) age/developmental specific concerns related to short term or chronic exposure, & c) concerns for those w/ pre-existing eye/skin conditions after experiencing short term or chronic exposure?

2nd, have studies been done looking at the impacts on the built environment's... 2/
microbiome, & the subsequent impacts on human health? And for this 2nd question, not just relative to Far UVC, but also for more traditional upper room UVGI systems.

Manufacturers are already marketing fixtures exposing occupants to Far UVC. Do the answers to either of the... 3/
Read 4 tweets
15 Aug
This is an all hands on deck moment. In-person school is starting. W/ the #DeltaVariant, even w/ the majority of the relevant strategies in place, it’s going to be difficult to prevent transmission in our schools (linkedin.com/pulse/in-perso…). 🧵1/

#ksed #ksleg
In an elementary classroom w/ unvaxxed students, generally ASHRAE compliant ventilation/filtration, the addition of (1) portable HEPA filter unit, & theoretical 100% mask wearing (double layer cloth mask), max exposure is only about 1.2 hrs before an additional student... 2/
is potentially infected at full occupancy (assuming 1 infected student is present).

Accounting for the potential reality of younger kids not always effectively wearing their masks (50% mask wearing), the max exposure is under an hour before an additional student is infected. 3/
Read 17 tweets
5 Jan
These are the type of actions our pharmacies, hair salons, retail stores, offices, universities, k-12 schools, individual residences, etc., need to be taking, particularly w/... 1/

@KDHE @LDCHEALTH @lawrenceks @douglascountyks @UnivOfKansas @usd497 @LawrenceChamber #ksleg #ksed
a more transmissible strain spreading in the U.S. & months left before vaccination levels are where needed to be.

CO2 levels can be used to estimate ventilation levels, though it's important to account for factors like the number of people present, the size of,... 2/
the space, & the use of portable air cleaners. Pages 23-24 of this document from @HarvardChanSPH & @j_g_allen provide a means for estimating ventilation rates based on measured CO2 levels. 3/

schools.forhealth.org/ventilation-gu…
Read 16 tweets
3 Jan
I would challenge your point that “No matter what we do, resources will remain scarce and people will compete over them.” First, there’s an abundance of evidence from the archaeological, historical, & contemporary ethnographic records of individuals & groups cooperating... 1/
(employing some or all of Ostrom’s principles) to survive in environments of scarce resources (& not just hunter/gatherer groups). Not saying the evidence for competition (including violent competition) isn’t also there, or that the competition between groups isn’t also... 2/
what often drives the cooperation among group members (because it does), only that cooperation seems to have been most effective when these principles are applied (even as part of a larger competition between groups).

Cooperating (& squashing toxic individualism) was... 3/
Read 17 tweets
22 Sep 20
Sure. I think that’s great advice, whether or not we’re in a pandemic. As high performance bldg consultants, we’ve been doing that since last March. Engaging school districts to help them work through building/behavioral strategies for reopening relevant to their situation. 1/
As part of that effort we also developed a viral infection risk estimator to help districts (in conjunction w/us, by themselves, or w/ other consultants) evaluate the most effective strategies room by room. Particularly important when resources are limited. I know other... 2/
consultants have been doing similar things (though perhaps not the behavior focus or developing calculators).

But there are limits to such efforts, or other local partnerships w/ businesses, short of a nationally coordinated effort to reopen schools. Decades of deferred... 3/
Read 14 tweets

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