1/ Concerns about under-ventilation of indoor spaces are FAR from new. Here are just 3 of many examples.
2/ Ben Franklin (18th century): "I am persuaded that no common Air from without, is so unwholesome as the Air within a close Room, that has been often breath'd and not changed" Franklin advocated exposure to fresh air & including open windows when sleeping.
3/ Florence Nightingale (mid 19th century): “Keep the air the patient breathes as pure as the external air, without chilling him.”
4/ Florence Nightingale: And poorly ventilated air is “stagnant, musty, and corrupt as it can by possibility be made [and] [i]t is quite ripe to breed small-pox, scarlet-fever, diphtheria, or anything else you please.”
5/ Max von Pettenkofer (mid 19th century): Recommended a maximum acceptable CO2 concentration of 0.1% (1,000 ppm).
6/ There are many more examples from 19th century and a lot during 20th century. Poorly ventilated spaces are inexcusable and unhealthy, & we can deal w/ the issue of poor outdoor air quality that enters buildings. It is not rocket science.
• • •
Missing some Tweet in this thread? You can try to
force a refresh
1/ Proven Technology. The cost to put a very good portable HEPA filtration system in a classroom that typically holds 24 or 25 students is approx $10/student/yr (year 1), with recurring filter & energy costs of around $7/student/yr. Per year. Not per day, week, or month.
2/ The system can often yield an equivalent of 3 or more ACH &, at ventilation rates I have seen in a majority of schools in Texas, 60-75% overall reduction in inhaled dose of virus-laden paricles in shared air.
3/ In the US we spend approximately $15,000/year to educate a SINGLE student. To effectively reduce virus-laden particles in classroom air would add a whopping $7-10/student each year to this total. Two Grande Frappaccunios, folks. Proven technology.
1/ Proven and unproven technologies. We have proven technologies for removing virus-laden aerosol particles from air: Increased ventilation, portable HEPA filtration systems (properly sized for space), and advanced MERV-rated filters (12 or 13) if mechanical system can handle.
2/ We have a proven technology that will inactivate viruses in aerosol particles - upper-room UVGI.
3/ These technologies have been proven for many decades, studied by many independent researchers for their effectiveness and published in peer-reviewed journals (which means even more analysis by independent researchers).
1/ Recently spoke with an official for a private multi-school organization that has large garage-door-like openings on every classroom. I was asked about ventilation with what amounts to nearly an entire wall open to the outdoors.
2/ This is similar to research that @JohnnyGrinch & I did a few years ago on ozone decay rates in residential garages in Austin. This work required simultaneous analysis of air changes per hour in garages (abstract only here) sciencedirect.com/science/articl…
3/ In 12 garages @JohnnyGrinch measured a mean of approximately 0.5 ACH in garages w/ doors closed (range from close to 0 to 0.8/hr. A limited amount of experiments were done with the door completely open.
1/ I am entirely with @j_g_allen on this & have also been since last summer. This should not have been such a big deal, and just think if schools had been listening to the advice of good building scientists starting 10-11 months ago.
2/ @Portland_State does not have abundant resources. But we mobilized a team quickly in April '20, developed a plan, & spent the summer working hard to implement. Increased ventilation, MERV-13 filters where possible, portable HEPA air filtration in appropriate classrooms ..
3/ Reduced occupancy, physical distancing, required masks, revised schedules to allow more time between class use of rooms (to help flush rooms of any virus-laden particles before the next class enters).
Some highlights. Schools in US (in general) have been woefully under-ventilated even before COVID-19.
2/ Increase ventilation. Combine use of outdoor air supply & portable HEPA filtration to yield > 6/hr air change rate. For schools w/ mechanical systems, open outside air dampers and disable demand-control ventilation if it exists.
3/ It is important to flush out those classrooms even when students and teachers are out of them for some time.
1/ Investment in engineering and computer science education has a significant return on investment (ROI) to states.
Proud of the great ROI that the Maseeh College of Engineering and Computer Science provides the State of Oregon.
2/ Every dollar that the State spends on helping to educate one of our students yields a 320% ROI over 10 years, or 12% compounded annually.
3/ Based on a detailed analysis of graduates who stay and work in Oregon, their starting salaries, incremental annual salary increases, and use of a State income tax calculator ….