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Dr. Richard Corsi

Feb 10 • 11 tweets • 2 min read

1/ Inhalation dose of virus-laden respiratory aerosol particles w/ at least one infector in shared indoor space (two contrasting scenarios).

Everyone wearing a (mediocre vs. high-quality) mask vs. nobody wearing a mask.

2/ Everyone wearing a mask serves to reduce emissions, lower concentration in air, and reduce inhalation by receptor. Nobody wearing a mask leads to neither benefit.

3/ Let's assume mediocre cloth masks (or poorly fitted better masks) yield 50% reduction at source and receptor vs. 95% for high quality masks with good fit & compare to no masks at all (lifting the mask mandate and forgetting about sources amongst the population).

4/ The benefit of a mask mandate with everyone wearing mediocre masks is an approximate 4 x lower inhalation dose than nobody wearing a mask.

5/ The benefit of a mask mandate with everyone wearing high-quality masks (N95 masks) w/ good fit is 400 x lower inhalation dose than nobody wearing a mask.

6/ of course, these are extremes and there is a lot of in between. The main point is that lifting the mask mandate if there is an infector present will dramatically increase inhalation dose receptors if the infector and receptor are each not wearing masks (by 4x to 400x).

7/ As I have written about since the summer of 2020, the dose makes the risk of infection. corsiairquality.wordpress.com/2020/08/19/the…

8/ So, without masks and with a more transmissible variant that is looking like the infectiousness of measles in our midst, logic and some simple math (not rocket science) should raise concern regarding greater inhalation dose and many more infections.

9/ Increased ventilation and very good room-scale air cleaners can make-up for (negate) the 4 x increase in inhalation dose from universal mediocre mask wearing but cannot come anywhere close to a 400x increase from universal high-quality mask wearing.

10/ More to come on the importance of air cleaners and ventilation ... more now than ever, folks!

To clarify .. that should have been 4 x increase in inhalation dose when no masks replace mediocre universal masks and 400 x increase when no masks replace universal high-quality (N95) mask wearing. Original text above may have been confusing.

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Dr. Richard Corsi

@CorsIAQ

Jan 27

1/ A single filter on fan can work, particularly in smaller spaces than a #CorsiRosenthalBox. Here are some concerns w/ a single filter that are not pointed out in a recent paper, & that led to the design of the box approach.

2/ Added resistance on the fan motor.
This was one of my primary concerns initially. This leads to lower air flow + potential for motor burnout.

3/ The filter has to be changed more often than filters when operated w/ four or five in parallel. The issue here is whether people replace the filter frequently enough. If not, the resistance on the fan can become even greater and air flow and overall CADR decrease even more.

Read 5 tweets

Dr. Richard Corsi

@CorsIAQ

Jan 27

@UCDavisCOE

1/ COVID-19 is an airborne infectious disease. Lowering inhaled dose of virus-laden respiratory aerosol particles is critical for lowering probability of infection and adverse outcomes. So, what are we doing @UCDavisCOE?

2/ We have invested in 60 very good right-sized HEPA air cleaners placed in communal spaces throughout the college, materials to build 50 #corsirosenthalbox es for teaching labs and other spaces, & over 5,000 N95 masks for those who don't already have some.

3/ We are also encouraging outdoor meetings whenever possible (I enjoy seeing group meetings in the Kemper Hall courtyard!)

Read 5 tweets

Dr. Richard Corsi

@CorsIAQ

Jan 13

1/ Tweets comparing the #corsironsenthalbox and portable HEPA filtration, including my own. I want to be clear that this is NOT a competition. The whole idea behind a CR box was to provide a viable and effective option for those without the resources to purchase a HEPA system.

2/ In fact, both will absolutely lower respiratory aerosol particles that convey the Omicron variant or other infectious agents. Both will reduce your inhalation dose to these agents, and that reduces your probability of infection and possible adverse outcomes.

3/ The CR box has the advantage of being much less expensive and highly effective if constructed well, and also a cool project and learning exercise for many. It has the disadvantage of being homemade (quality of construction varies) w/ possible leakage if kicked, etc.

Read 7 tweets

Dr. Richard Corsi

@CorsIAQ

Jan 12

@CappaSnappa

1/ In case anyone wants to see data that show how effective the #corsirosenthalbox is for a home office and a classroom at roughly 1/4 the price of HEPA #1 (which is a good system). Submitted (in peer-review) paper by Team @CappaSnappa @UCDavisCOE.

medrxiv.org/content/10.110…

2/ By application of results, range of equivalent ACH in a typical 2-person dorm room = 20 to 27 (low to high setting). For comparison, hospital isolation rooms typically designed for > 12 ACH.

Range for a 700 ft2 classroom w/ 9 ft ceiling = 5.7 to 7.6 ACH (low to high setting).

3/ Don't let anyone tell you that we cannot DRAMATICALLY lower inhalation dose of virus-laden aerosol particles w/o huge cost, particularly in spaces w/o elevated ventilation or non-universal high quality mask usage. No rocket science, folks. Just do it!

Read 4 tweets

Dr. Richard Corsi

@CorsIAQ

Jan 8

1/ Since start of the pandemic there's been one obvious and absolute truth. COVID-19 is an airborne infectious disease. As such, to reduce chance of infection and community spread we must significantly reduce the amount of virus-laden aerosol particles that we inhale. Period.

2/ That was true every second of every day before vaccinations, and while vaccinations are critical for reducing severe outcomes of infection, we should still be doing everything possible to reduce our inhalation dose of virus-laden aerosol particles. The steps are simple, folks.

3/ Wear a high-quality mask (e.g., KN95 or N95) at all times while indoors w/ others outside your own family.

Avoid indoor spaces where people are not wearing high-quality masks or masks at all.

Where one has control, ventilate to a much greater degree.

Read 6 tweets

Dr. Richard Corsi

@CorsIAQ

Jan 5

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.

Read 8 tweets

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