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.
3/ "If the most efficient systems were installed "we could pass from 250 cases per 100,000 students (the alert level set by the education ministry) to a rate of 50 per 100,000."
Yep, its about lowering inhalation dose to virus-laden respiratory aerosol particles.
4/ Lower the concentration of virus-laden respiratory aerosol particles in classroom air by increased ventilation or appropriate filtration & you lower inhalation dose to those particles and reduce infections.
5/ Been that way from the start & has never changed. Along w/ many other dedicated colleagues, we've been speaking w/ the media, giving webinars, writing papers, op-eds, letters & more to try to get across importance of airborne respiratory aerosol particles & actions to lower.
6/ It's been so darn obvious (& frustrating) for 2 yrs.
We have had the tools all along to dramatically reduce inhalation of virus-laden aerosol particles in classroom and other building air, but largely failed (miserably) to make use of those tools.
7/ I've written often that to implement exceptionally effective tools in classrooms costs less than 0.03% of the cost of educating 1 student in the US. Perhaps over 2 yrs beyond the obvious we can start prioritizing health of students & their families in an effective way.
8/ And in doing so we can also makes school environments healthier during wildfire season, & for students and teachers with allergies, asthma, and more. None of this is rocket science, folks. Just do it!
Big goof. That should have been we CAN achieve 10 ACH as an equivalent --- ventilation + filtration ACH.
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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.
3/ When ozone is elevated outdoors or when (unfortunately) devices are used that generate ozone indoors, more of these indoor reactions occur.
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/ 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.
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.