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).
3/ Without any other ventilation, this is 2 x a hospital isolation room! Measurements of natural ventilation in my home garage with the large garage door wide open have been in the range of 15 to low 20s for ACH depending on outdoor wind conditions.
4/ Upshot - Aerosol particle concentrations in the dorm room drop to a tiny fraction of what they would have otherwise been. Just sayin', folks.
5/ For a 700 ft2 classroom the eACH increase using a #CorsiRosenthalBox at 800 cfm is 7.6 ACH. When I apply ASHRAE 62.1 2019 calcs to K-12 classrooms I've studied in Texas and then convert to ACH, values typically range between about 2.5 to 3.5/hr.
6/ Adding these values to 7.6 ACH equivalent yields 10.1 to 11.1 ACH --- that's almost a hospital isolation room.
7/ Don't tell me that we cannot make classrooms MUCH safer without a small investment of time and money.
8/ The capital, electricity, and recurring filter replacement cost for a classroom of 25 students works out to an average of about $3/student/year over three years.
9/ That's one Venti Iced Coffee per student every year for a massive reduction in their exposure to virus-laden respiratory aerosol particles, wildfires smoke particles and more.
10/ The average cost of educating a student in the US is $13K/year. So, we are talking about $3K/year + $3 investment for a massive health benefit & reduction in probability of COVID-19 spread. That's a 0.023% increase, a Venti Iced Coffee, folks.
11/ That anyone has to think twice about this is painful. Just do it!
That is $13K + $3….
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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.
3/ If there is a silver lining that has come out of this H*O*R*R*I*F*I*C pandemic, it's that the public has started learning of the importance of indoor air quality, from sources to the importance of engineering controls & how buildings are operated, constructed, and maintained.
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.
3/ If source removal is not possible, then source reduction becomes important. Lowering density lowers the probability of a source being present, but does not assure removal of source. Everyone wearing high-quality, e.g., N95, masks dramatically lowers source emissions.
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.
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.
3/ Three criteria were considered for the device: (1) Effective, removing a reasonable amount of virus-laden aerosol particles from indoor air. (2) Inexpensive, much lower cost than HEPA air cleaners. (3) Open source, not a “money maker” for anyone or any organization.
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.
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).
3/ Data indicate CADR of 400 to 800 cfm depending on fan and fan speed. These results can then be translated to estimate benefits in actual building spaces.