1/ The governor's words might be turned on those making such absurd statements. Inhalation of aerosols that contain the SARS-CoV-2 virus causes COVID-19. Right-sized HEPA air cleaners can be effective at reducing aerosol concentrations in classrooms.
2/ It is one important intervention amongst others (vaccines, masks, ventilation, testing) & plays a magnified role when significant increases in ventilation are not possible, when children have masks off, and/or some are not vaccinated. But it provides benefit in all scenarios.
3/ There have been dozens and dozens of peer-reviewed papers in high quality journals by high quality researchers that reinforce the value of HEPA filters for lowering indoor aerosol levels, even during the past two years and in the context of COVID-19.
4/ Like so many others, the governors are not well read on this topic, not paying attention, or choosing to look the other way because it sounds too complex or may cost some money. Here is a result of a very simple calculation.....
5/ In the US it costs about $15,000/year to educate a single student. The cost (capital + recurring filter replacement + electricity) of placing a right-sized HEPA air cleaner in a typical classroom is just about $10 per year for every student.
6/ Think about that. The cost of reducing indoor aerosol concentrations that deliver SARS-CoV-2 to the respiratory systems of children is just under 0.07% of the cost to educate that child. Obvious benefits here, folks. No rocket science.
7/ @JBEYFS. Not sure where you are, but will try to provide some papers and also connect you with exceptional aerosol and building scientists in your region. Don't stop trying.

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More from @CorsIAQ

1 Jan
1/ Some thoughts spurred by the guidance below

6 eACH (ventilation + filtration) is somewhat arbitrary, but a reasonable guidepost. Keywords here are "at least." The allusion to 95% removal of contaminant in 30 min is a bit deceiving. It ONLY relates to after source is removed. Image
2/ For a well-mixed indoor air space, an increase in eACH from, say, 2/hr (unfortunately not untypical for K-12 classrooms) to 6/hr yields a maximum decrease in indoor aerosol concentration of 67% and not 95%. Starting at 3/hr = max of 50% reduction w/ increase to 6 eACH.
3/ And the net benefit is particle size dependent, as particle deposition to surfaces is a third sink (removal mechanism) that adds to removal by ventilation and filtration.
Read 18 tweets
23 Nov 21
1/ With COVID-19 on the rise (again). Remember, the SARS-CoV-2 virus is transported by respiratory aerosols. INHALATION of aerosols is the dominant transmission pathway. Many of us have not wavered on this fact since early in the pandemic. It's about inhalation dose, folks.
2/ Since the dominant pathway is INHALATION of virus-laden respiratory aerosols, then reducing inhalation dose of these particles or inactivating viruses in the particles is the answer to reducing infection (pre- or unvaccinated & even vaccinated breakthroughs).
3/ Science & engineering gave us all of the tools we need to drive this pandemic into the ground. Vaccinations are a gift handed to us on a silver platter. The rest is not rocket science. The rest should be common sense.
Read 7 tweets
29 Oct 21
1/ A Quantitative Risk Estimation Platform for Indoor Aerosol Transmission of #COVID19 (Open Access paper)

Some Cliff Notes in thread below.

2/ This paper offers a platform that is somewhat more mechanistic than traditional risk estimates for airborne infectious disease. It includes ability to include aerosol size distributions & emissions from infected individuals + particle fate mechanisms indoors.
3/ Insertion of control options (increasing ventilation, masks, filtration) in single zone systems can be employed. The model predicts particle deposition in the respiratory system of receptors & converts these to total volume of particle deposition.
Read 7 tweets
21 Oct 21
1/ Indoor Air Quality in Schools
Some slides from a presentation on indoor air quality in schools a decade ago. It contains reference to what I thought were important/insightful papers at the time. A lot more slides than shown here. Will post at corsiaq.com
Read 18 tweets
12 Oct 21
1/ Don't be fooled by some air cleaning companies that claim their device is highly efficient. When claims are made about removing 95% or 99% of particles from air, this nearly always refers to % of particles removed THAT FLOW THROUGH THE DEVICE (single pass removal efficiency).
2/ A device can be 99.5% efficient & highly INEFFECTIVE if it has little flow moving through it. The product of fractional removal efficiency (max = 1.0) & volumetric flow rate (e.g. cubic feet per minute) is the important parameter (& known as CADR or Clean Air Delivery Rate).
3/ Example - Company for device 1 claims it removes 99.5% of particles from air (fractional single-pass removal efficiency = 0.995), but the device moves only 30 cfm of air (CADR = 0.995 x 30 cfm = 30 cfm).
Read 5 tweets
19 Sep 21
1/ Inhalation Dose
It's been about inhalation dose from day 1. We have not kept our eye on the ball. Critical pre-vaccination. Critical post-vaccination. Been writing & speaking about this for nearly 20 mos. Reducing inhalation dose is a must. Come on folks, just do it!
2/ Reducing Inhalation dose using layered interventions is still important, whether unvaccinated or vaccinated (breakthrough cases), in close contact (near field) or far field in the same indoor space, in a car or classroom, in a restaurant or apartment, young or old.
3/ Inhalation dose associated with virus laden aerosol particles is defined by the same variables (whether close contact or far field ---- don't bicker about one or the other - I've previously tweeted about this):

Dose(inhal,i) = C(i) x B x t x fdep(i)
Read 25 tweets

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