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Joshua C. Agar Profile picture
@JoshuaCAgar
Jan 8, 2022 • 21 tweets • 9 min read • Read on X
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Admittedly there's a research gap concerning face shields since they are mainly intended for hospital settings, hence scenarios limited to hospital settings. The general consensus is that face shields are intended for ballistic droplets, not for aerosols.

Below are the studies:
Lindsley et al. (2014). Efficacy of Face Shields Against Cough Aerosol Droplets from a Cough Simulator

Face shields are evaluated to stop the initial impact of the cough which brought heavy droplets, however, airborne droplets still make way around.

ncbi.nlm.nih.gov/pmc/articles/P…
Akagi et al. (2020). Effect of sneezing on the flow around a face shield. Phys. Fluids 32. doi:10.1063/5.0031150

A numerical simulation of a sneeze on a face shield, showing that transient effects actually directs aerosols inside even during impact.

aip.scitation.org/doi/10.1063/5.…
Pan et al. (2021) Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield, Aerosol Science and Technology, 55:6, 718-733, DOI: 10.1080/02786826.2021.1890687

Face shields are rated as the poorest protective layers.

medrxiv.org/content/10.110…
Salimnia et al. (2021). A laboratory model demonstrating the protective effects of surgical masks, face shields, and a combination of both in a speaking simulation

An experimental study evaluating little to no contribution of face shield.

pubmed.ncbi.nlm.nih.gov/33485923/
Bagtasa (2021). Efficacy of face shields to ambient aerosols in local indoor and outdoor setting. 2021: Proceedings of the 39th Samahang Pisika ng Pilipinas Physics Conference

Evaluating that face masks are the ones doing the work, not face shields.

proceedings.spp-online.org/article/view/S…
Wendling et al. (2021) Experimental Efficacy of Face Shield and the Mask against Emitted and Potentially Received Particles, J. Environmental Research and Public Health

One of the flawed studies conducted by medical professionals. Fails on equipoise.

pubmed.ncbi.nlm.nih.gov/33671300/
A visualization of TU Delft shows what happens to the emissions in the first place when the face masks are interfering:

If the face mask are already directing the emissions to the sides and the back instead to the front, what's the use of Wendling's setup?
Verma et al. (2020). Visualizing droplet dispersal for face shields and masks with exhalation valves

A visualization experiment by the Florida Atlantic University showing that face shields are poor source control... They don't stop aerosols at all.

aip.scitation.org/doi/10.1063/5.…
Most of these studies were derived from hospital settings, therefore they perceived sporadic (i.e. cough, sneezes, speaking) emissions as the high risk scenarios, and focused only for that scenario.

Here is what happens at different angles of approach:
If the cough is coming from behind, the wearer of the face shield is practically screwed:
Here is what happens when you walk in an indoor space (close spaces, crowded places) saturated with airborne particles while donning a face shield:
Faster accumulation of airborne particles if you're looking side-to-side while walking:
A face shield provide a place for retention of airborne particles:
If there's wind potentially carrying SARS-CoV-2 coming from behind:
Similar scenario, only at an oblique angle:
As Dr. Jimenez has said, face shields are useless against Covid-19, now that the understanding that it is airborne. When face shields are coupled with face masks, face masks are the ones doing the work while face shields do nothing.

There are in-fact, other atmospheric consequences of face shields that lead to the increase in infectivity of SARS-CoV-2.

This is the extended abstract of the conference paper that I'll be presenting two weeks from now.
If one insist on doing RCTs on face shields in public settings, despite these studies and despite the fact that face shields are physical items, not medicine, maybe for truthfulness sake, include the Pontresina Case
thelocal.ch/20200715/only-…

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More from @JoshuaCAgar

Joshua C. Agar Profile picture
Feb 28
I tried to start my class w/ a classroom chat, asking their reactions on the current events.

Students told me that they were not keeping tabs on the current events, as they were drained w/ their academic load.

There has to be an energy to spare if one wants people to care.
As I commute home one night, via the EDSA Carousel Bus, I had a long walk and a long climb to get on the bus.

Some people who boarded the bus at the same time, the moment when they sat, fixate themselves on the Reels on Soc Med, with some coming from the fake news purveyors.
Parents, tired at work, come home to only encounter their children question their political choices at the family table. As they have no longer the energy to spare to even engage in political discussion and welcome the prospect of them being wrong, they will shut it off.
Read 7 tweets
Joshua C. Agar Profile picture
Feb 26
The sense of elitism prevents us into looking deeper as to why most Filipino citizens make questionable choices at the ballot box.

Empathy requires us to understand that they are also overwhelmed by everything and as a result, tend to conserve their energy.
Reading posts such as this requires energy.

Processing the message requires energy.

Inquiring past the comfort zone requires energy.

Learning about all the candidates requires energy.

Combating the cognitive dissonance due to conditioning infos shoved on them requires energy.
But...

Working for make a living requires tremendous energy.

A hellish commute drains energy.

People require energy to get out of their comfort zones.

People require energy to make realizations and pull off rectifications.
Read 13 tweets
Joshua C. Agar Profile picture
Nov 14, 2024
I advise people to subscribe to vital weather information from weather agencies and reputable scientists with their reputations at hand, since accountability forges trust.

I also would want to you to sit through and read through this thread that gives complementary information🧵 Image
It is also important to anticipate and know where the winds will be coming from due to what's called wind exposure affecting the characteristics of typhoon winds, on how strong and/or consistent they will be depending on your location. Image
Winds at sea will experience little to no dissipative effects. Therefore the winds will be consistently strong.

The peak gust (bugso) will not be far on how strong the sustained winds will be. Image
Read 30 tweets
Joshua C. Agar Profile picture
Dec 21, 2023
Our study that developed CO2 monitors that informed occupants of the relative risk that they may be subjected to due to airborne diseases transmitted through shared room air transmission has been published. #CovidIsAirborne

doi.org/10.3389/fbuil.…
Image
Using a multivariate method, the ventilation rates of different indoor spaces are determined and used for the subsequent computations using the Wells–Riley model to derive the respective infection risk, particularly of COVID-19. Image
"Infection risks are determined to be higher in indoor spaces with low ventilation rates. However, having high ventilation rates does not mean low infection risks as smaller spaces will also have higher infection risks."
Image
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Read 7 tweets
Joshua C. Agar Profile picture
Dec 12, 2023
Part of the PowerPoint presentation to be presented on Thursday:

How aerosols move Image
Conservation of Mass
Image
Image
Infection risk modeling

Image
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Read 4 tweets
Joshua C. Agar Profile picture
Apr 23, 2023
High humidity also attributes to high infection rates and deaths due to Covid-19.

Shown below are the trends derived from the correlation between Covid-19 deaths and relative humidity. 60% RH is the Goldilocks Zone: lesser or greater than that results in the increase of the risk Image


Why 60%?

It has to do with two things: (1) lessening evaporation rates due to inhomogeneous mixing and (2) rate of condensation which attributes to the increase of pore pressure within the mask.royalsocietypublishing.org/doi/10.1098/rs…
Countries above the tropics experience case surges during their winter season when relative humidity is low. The hot and humid respiratory emissions will mix with the cold and dry indoor air resulting in higher evaporation rates,
Read 7 tweets

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