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Feb 2 • 4 tweets • 3 min read
Highly recommended! Detailed summary of the main engineering controls for airborne infection control to reduce transmission indoors:
#Ventilation #Filtration #UVGI
👇
#DoAllTheThings! Implement multiple engineering controls to reduce airborne infection and improve indoor air quality
#Ventilation
#Filtration
#UVGI Image
If you want a partial data dump of my brain, the Time Magazine article is a great summary. time.com/6143799/covid-…
For more on UV, this 1h 35min webinar featuring David Sliney, @Don_Milton, Ed Nardell (who wrote the Time Magazine article), @WBahnfleth, and Paul Jensen is a great introduction. Use it for CE credits! ghdcenter.hms.harvard.edu/keeping-public…

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More from @DavidElfstrom

David Elfstrom Profile picture
Jan 20
Having a CO₂ meter with visible display can enable an educator to be a manual version of a demand-controlled ventilation system, with control over the indoor environment using windows (Source: Di Gilio et al 2021, pubmed.ncbi.nlm.nih.gov/34224708/) #COVIDCO2
HT @Billius27 "Fig. 5 are shown the ...
@Billius27 If a CO₂ display was in my daughter's mechanically ventilated classroom, her teacher might have opened the windows, or moved to another room after seeing rising levels. Principal: waiting for parts to repair the HVAC system. Daughter developed common cold symptoms 48h later. Image
@Billius27 Here is one of many reasons WHY we want to monitor and take action on CO₂ concentrations:
Read 4 tweets
David Elfstrom Profile picture
Jan 12
Very exciting news on the #corsirosenthalbox front! @CorsIAQ & @CappaSnappa thanks for the (Elfstrom 2021) reference, it made my day! Some comments & questions follow: /1
"AHAM recommends that CADR is 2/3 of floor area" Yes, it's floor area = 1.55 x sqft. That's for 8' ceiling with 1 ACH residential outdoor air exchange, described in Annex E of AHAM AC-1 2020: /2
"Our method allows for determination of CADR values above the 450 CFM upper limit of the standard method AHAM 2014" Yes, larger test chambers are needed!
This has been updated, upper limit now 600 ± 10 CFM except for pollen which is 450 ± 25 CFM /3
Read 8 tweets
David Elfstrom Profile picture
Jan 11
The air cleaner purchased by @nseducation for schools has a Clean Air Delivery Rate almost HALF of a common retail unit and may create secondary products by reacting with gas phase contaminants in a poorly ventilated room using photocatalytic oxidation #nspoli /1 Guardian Beyond Air F159E: ...
As seen in the photo, it's not running on its highest setting. For #ventilationequity in non-mechanically ventilated classrooms, should be a min 15 CFM per person, or 375 CADR for 25 people, AND at an acceptable noise level. How many per classroom? #DoTheMath! /2
Don't get me wrong, any filtration is better than nothing! But it's a mere band-aid over a gaping wound.
A DIY $120 #corsirosenthalbox will beat the air cleaners purchased by @nseducation AND can be used in STEM lessons! See cleanarair.com /3 Screen capture of web site
Read 15 tweets
David Elfstrom Profile picture
Dec 14, 2021
My wife & daughter traveled to @sickkids @SickKidsNews today for an appointment.

Several lapses occurred at screening. Most egregious:
They were made to remove their CA-N95 respirators for the blue surgical mask, shown below.

Let's go through all of them: /1 Photo of left hand holding ...
Your policy is to protect everyone, especially those at higher risk of COVID-19. How is downgrading masks consistent with that? What is the "right" amount of protection, anyway?
My wife and daughter were NOT offered the option of masking overtop. /2 Several extracts from unive...
Health Canada:
"If you're at higher risk, it's even more important to consider wearing a respirator if one is available to you"
"Respirators are designed to fit snugly on the face, which may allow for a better fit than a medical mask" /3
canada.ca/en/public-heal…
Read 11 tweets
David Elfstrom Profile picture
Dec 9, 2021
Swiss study finds SIX TIMES the cases in poorly ventilated classrooms (those with over 2000 ppm CO₂) compared to better-ventilated ones. #COVIDCO2
#Ventilate2Educate #COVIDisAirborne
H/T @SamJCauston
swissinfo.ch/eng/society/st…
More details on the Swiss CO₂ classroom study here: empa.ch/web/s604/covid…
For those school administrators who say “we have a ventilation system, it meets or exceeds ASHRAE standards”—That's not enough. You MUST monitor #COVIDCO2. My daughter's fully ventilated classroom, from her backpack monitor, yesterday vs today:
Read 7 tweets
David Elfstrom Profile picture
Dec 9, 2021
While #Ventilate2Educate is geared towards schools, we can #Educate2Ventilate with simple directives for small businesses & organizations. Simple low-cost changes can make for an enormous indoor air quality improvement. Low-rise small commercial buildings are everywhere. Simplified schematic of small business rooftop unit: Maximiz
These simple ventilation actions and more are described on the CDC's Ventilation in Buildings Page: cdc.gov/coronavirus/20…
Idea for a local Business Improvement Area #Educate2Ventilate campaign: Team up with a local HVAC contractor and visit all the storefronts with a CO2 meter to promote simple changes to improve indoor air quality. Add energy efficiency measures too.
Read 5 tweets

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