Richard Corsi, PhD, PE (Texas) Profile picture
Dean of Engineering, University of California, Davis. Faith in younger generations. Lover of dogs, music, & technology for the good of all of society.
Sue Strong 🦋🌻🚜🇺🇦#StandWithUkraine 🇺🇦🚜🌻🦋 Profile picture NotOralHistory, but actually *yes we are* Profile picture Perpetual Mind Profile picture Aviva Gabriel Profile picture Mong How Ooi Profile picture 31 added to My Authors
May 15 16 tweets 6 min read
1/ Had a few folks ask where I’ve been in twitter discussions of COVID-19. Still here & doing what I can to promote & act on lowering inhalation dose of virus-laden aerosol particles. Continuing discussions w/ reporters & policymakers (when asked), but largely in the shadows. 2/ Been keeping up w/ twitter banter when I have breaks, some of which has been great & some enormously frustrating. My position as dean of @UCDavisCOE is demanding but exciting, and has been job 1 for the past 7 months. Hopeful to engage a bit more once the spring term ends.
May 6 4 tweets 2 min read
More periodic table tiles in front of Peter A Rock Hall @ucdavis.

A fairly important atom! 1/ 2/
Apr 8 11 tweets 2 min read
1/ 15 minute Rule?

Remember that what matters is the inhalation dose (D) - which is equal to C x B x t x f
C = concentration of SARS-CoV-2 virions in breathing zone air (inside of mask if mask worn) (#/L) embedded in respiratory aerosol particles.
B = ..... 2/

B = Respiratory minute volume (L/min) (aerobic exercise gives a much larger B than you have reading this at your computer --- perhaps 5 to 10 x)
t = time in indoor environment shared by an infected individual (min)
f = ....
Mar 22 9 tweets 2 min read
1/ Important study of over 10,000 classrooms.

Upshot = lowering concentration of virus-laden respiratory aerosol particles in classroom air lowers inhalation dose of these particles and significantly reduces infection. Always been about this, folks.… 2/ Increasing ACH from lower than 2.4 to 2.4/hr - infections reduced by 40%. To 4 ACH lowered by 66.8%, to 6 ACH lower by 82.5%. With an appropriately-sized portable HEPA system or a #CorsiRosenthalBox we cannot achieve 10 ACH.
Mar 22 18 tweets 4 min read
1/ Very interesting study on effects of ozone on adolescent depression. The study focused on elevated ozone concentrations outdoors. 2/ Remember that ozone of outdoor origin penetrates into buildings and reacts with indoor materials & unsaturated organic compounds in indoor air to form a wide range of reaction products, many of which are lacking tox studies.
Mar 18 6 tweets 2 min read
1/ Almost 22 years ago I wrote an article for Environmental Manager entitled Indoor Air Quality: A Time for Recognition. I called for new clean air act amendments that address indoor air quality due to its profound impacts on human health.… 2/ From well before that article to the 22 years since I have tried to be a relentless advocate for formal recognition of indoor air quality and its importance, often feeling defeated, as I know many, many of my wonderful colleagues have as well.
Mar 18 12 tweets 2 min read
1/ A context slide from my CITRIS webinar on 3/16/22.

We know it is possible to achieve a CADR > 800 cfm for a Corsi-Rosenthal box. So, let's compare its impact in a realistic dorm room & classroom relative to air changes per hour in, say, a hospital infection isolation room. 2/ In a standard 2-person dorm room (where masks are unlikely to be worn when two people are sleeping 10 ft away from one another for 8 hours!) the CR box yields an aerosol particle reduction equivalent to 24 air changes per hour (ACH).
Mar 16 5 tweets 1 min read
1/ In the indoor air quality field, source removal (or avoidance of ever having the source in a space) is a fundamental principle.

“If there is a pile of manure in a space, do not try to remove the odor by ventilation. Remove the pile of manure.” Max von Pettenkofer (1858) 2/ During the pandemic that means doing all that's possible to avoid having infected persons in a space with others. Stay home if feeling symptoms. Test and isolate.
Mar 15 9 tweets 3 min read
1/ Really excited to get this paper into the pipeline for peer review. See…

Involves a novel method to assess near- and far-field exposures using specific terpenoids/VOCs in breath mints & a PTR-ToF-MS. Teaser below for distance from human source. 2/ Results, of course, are limited to the specific chamber and ventilation assembly (27 m3 chamber at 3 ACH w/ top-down ventilation).
Mar 7 29 tweets 10 min read
1/ 3 hours in the late night & a seed tossed into the social media wind. Origin of the #CorsiRosenthalBox.

There were 2 motivations for the concept.

Motivation 1. Make effective air cleaning more accessible to those who cannot afford $300 HEPA air cleaners. 2/ Motivation 2. Help schools employ effective air cleaning at a cost that would not be prohibitive given financial constraints. In summer 2020 school districts seemed overwhelmed, confused, & vulnerable to purchasing shiny objects that might not actually be all that effective.
Mar 6 13 tweets 5 min read
1/ I always go in for my asymptomatic PCR testing @ucdavis on Sunday mornings & take the time to walk around campus before & after. It is such a gift to work at a great university w/ such a wonderful campus. A few images taken on those walks today & previously ..... 2/ Our beautiful arboretum - Such a nice play to walk away from the office to clear one's mind and get some exercise.
Mar 5 10 tweets 3 min read
1/ It would be easy to put a #CorsiRosenthalBox in a 3 m3 chamber with 0.05 ACH, inject particles, switch the system on, and show a dramatic downward trajectory of particle concentrations to effective 0 ug/m3 in 10s of seconds. But we do not do that, for it would be deceiving. 2/ Instead, studies are being done in actual classrooms, home environments, etc., and showing remarkable effectiveness at reducing aerosol concentrations. Further, experiments are being done to determine highly-relevant metrics like clean air delivery rate (CADR).
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.
Jan 27 5 tweets 2 min read
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.
Jan 27 5 tweets 2 min read
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.
Jan 13 7 tweets 2 min read
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.
Jan 12 4 tweets 2 min read
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.… 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).
Jan 8 6 tweets 2 min read
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.
Jan 5 8 tweets 2 min read
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.
Jan 1 18 tweets 3 min read
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.
Dec 31, 2021 7 tweets 2 min read
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.