1/ Reducing respiratory aerosol particle concentrations in dorm rooms.

I have heard from parents who have children returning to dorms at universities across North America. The #corsirosenthalbox can help with these situations a lot! Really a lot, folks. read on.
2/ 8 hours unmasked while sleeping each night w/ 2 or 3/room should be a concern regarding infection, not to mention being poorly-masked while studying with others in the room.
3/ Increasing ventilation will help to reduce respiratory aerosol particle concentrations to the extent it is possible, but will be limited by system constraints or inoperable windows.
4/ Quick calculation --- The corsi-rosenthal box (well sealed and on top fan speed with four parallel MERV-13 filters) can yield clean air delivery rates across a spectrum of relevant particle sizes of 600 to 800 cfm. So what does that mean in a dorm room?
5/ When applied to a 200 square foot dorm room w/ a 9 ft ceiling, the corsi-rosenthal box yields a respiratory aerosol reduction equivalent to 20 to 27 air changes per hour, much more than commercial airliners or isolation rooms in hospitals. So, what's the cost?
6/ There is a time cost. A student wishing to make one would need to read instructions. See, for example, cleanaircrew.org/box-fan-filter…. The time to build varies by individual. It usually takes me 60 to 75 minutes for proper sealing. Others claim less time. Dollars?
7/ The materials needed to build a good air cleaner will run about $80-85 (US). However, it is easy to get bulk discounts on filters if groups of students purchase together. In that case the cost can be less than $60/unit.
8/ So, think about this - about $60,000 for 1,000 dorm rooms for equivalent of 20+ ACH. $300,000 for 5,000 dorm rooms, etc. And likely to remain effective for 6+ mos.

Rocket science? Nope. A little #citizenengineering, folks, & signif' infection reduction when masks not worn.

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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
31 Dec 21
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.
Read 7 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

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