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2 Feb, 13 tweets, 6 min read
ASHRAE guidance on in-room air cleaners for reducing COVID-19 in the air (Jan 21, 2021)
@ShellyMBoulder
Link (PDF): ashrae.org/file%20library…
/1 IN-ROOM AIR CLEANER GUIDANCE FOR REDUCING COVID19 IN AIR IN
Stick to the basics of filtration. Beware of some technologies used by portable air cleaners: Ionizers, UV-PCO and other names may claim to remove or destroy contaminants but may convert them to other compounds that may be harmful
Link (PDF): ashrae.org/file%20library…
/2 In-room air cleaners may contain one or more technologies de
Good example of sizing a portable air cleaner for a classroom with a MERV-8 filter already present in the HVAC system to achieve 6 air changes per hour equivalent.
Link (PDF): ashrae.org/file%20library…
/3 Example of how to choose the right size: A 45 x 20 ft (14 x
Consider noise level for a portable air cleaner. Beware of construction-grade air scrubbers as they are usually loud.

Two units operating at a low speed may be quieter than one larger one.

Link (PDF): ashrae.org/file%20library…
/4 How do I select the right one? 1) Confirm the CADR of the un
US EPA: Air Cleaners and Air Filters in the Home
Link: epa.gov/indoor-air-qua…
/5 Screen capture of web page
Decibel Addition and Subtraction Calculator, to determine total noise level from more than one portable air cleaner
Link: noisemeters.com/apps/db-calcul…
/6 Screen capture of web page
Testing mobile air purifiers in a school classroom: Reducing the airborne transmission risk for SARS-CoV-2
J. Curtius, M. Granzin, J. Schrod
medRxiv 2020.10.02.20205633; doi: doi.org/10.1101/2020.1…
/7 Screen capture of web page
Don't be like Quebec. /8
HRAI has easy-to-read guidance on schools
Link (PDF): hrai.ca/uploads/userfi…
/9 January 2021: Reducing the Risk of Virus Transmission via HV
IAQ & COVID In Commercial Buildings with Dr. Jeffrey Siegel @IAQinGWN. A 1-hour webinar from Jan 26 2021 hosted by @HRAI_Canada /10
Note this example assumes most SARS-CoV-2 is in aerosols 1-6 µm. This may not be correct; smaller sizes may dominate.
The "Isolation of SARS-CoV-2 from the air in a car" study was only able to culture virus from 0.25-0.50µm sizes doi.org/10.1101/2021.0…
BUT you don't need to buy a portable HEPA!
A box fan, packing tape, and MERV-11 filters can beat a high end HEPA, because of the total volume of air it can push and cleans on multiple passes. It isn't pretty but it works. /11
/12

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More from @DavidElfstrom

David Elfstrom Profile picture
31 Jan
New plain-language guidance for reducing virus transmission in schools using HVAC systems, by @HRAI_Canada

#Ventilatio, #filtration, UV, CO2 meters, humidity, portable air cleaners

Link (PDF):
hrai.ca/uploads/userfi… Reducing the Risk of Virus ...
HRAI has also reached out to school boards and Education Ministries Canada-wide to ensure decisions concerning #ventilation and #IAQ in schools are informed by the best available information.

mediaedgedigital.com/supplierinsigh…
Since children are likely to be the last to receive a vaccine, we must continue to push for indoor air quality funding.

The lasting benefits of better academic performance and reduces absenteeism of students & staff alike are worth it. /3
Read 4 tweets
David Elfstrom Profile picture
15 Jan
New preprint from J Lednicky & al: Isolation of SCV2 from air in a car driven by a COVID patient with mild illness. (Jan 15 2021).
While virus detected at all sizes, "Remarkably, viable virus was only detected in particles 0.25um to 0.5um)"
doi.org/10.1101/2021.0…
@jmcrookston
Automobiles are one of the worst places to be. Roll down windows, wear good, well-fitting masks, and especially use NO recirculation.
"The patient drove the car for 15 minutes w/windows closed and the A/C on, then parked it and exited, leaving the windows up and the air sampler running for an additional 120 minutes. Total collection time of 135 min to
sample 1.22 m3 of air within the vehicle"
Read 4 tweets
David Elfstrom Profile picture
14 Jan
BREAKING! Ontario Society of Professional Engineers @O_S_P_E calls on the Ontario government @ONgov to IMMEDIATELY address the #airborne transmission of COVID-19 to help slow the spread.

Summary thread follows
/1
ospe.on.ca/featured/engin…
"OSPE and its engineers believe a key piece to our defence against this virus has not been properly addressed by the Ontario government - the need for proper #ventilation and air #filtration to stop the spread of the virus via #aerosol particles"
/2
"OSPE believes that airborne transmission is one of the main reasons why we are seeing so many outbreaks in schools and long-term care facilities across the province"
/3
Read 9 tweets
David Elfstrom Profile picture
11 Jan
🇨🇦EXCELLENT! Public Health Agency of Canada @GovCanHealth today (11 Jan 2021) releases a full pandemic #ventilation guide!

PROVINCES break out the #scicomm, update regulations, investigate ventilation in LTC, schools, & other congregate settings

Link: canada.ca/en/public-heal… Screen capture of web page titled: COVID-19: Guidance on ind
The new Public Health Agency of Canada #ventilation guidance references the Aerosol FAQ & work of @kprather88 @linseymarr @ShellyMBoulder @jljcolorado @ASHRAE_Journal & many others

FAQs on Protecting Yourself from COVID-19 Aerosol Transmission, link: tinyurl.com/FAQ-aerosols Screen capture of the top of the FAQs on Protecting Yourself
Read 4 tweets
David Elfstrom Profile picture
9 Jan
Published today (8 January 2021) Public Health Ontario's FAQ on Portable Air Cleaners and Transmission of COVID-19.

A good resource, and quite the opposite to what INSPQ released for Québec, also today.

PDF: publichealthontario.ca/-/media/docume… Screen capture of the top o...
Ontario's FAQ comes five months after @jljcolorado's 22-tweet thread on air cleaners, and earlier work by @ShellyMBoulder. Be ahead of the curve, follow them.
FOIRE AUX QUESTIONS - L’utilisation de dispositifs portatifs de filtration d’air et la transmission de la COVID-19 (PDF): publichealthontario.ca/-/media/docume… FOIRE AUX QUESTIONS L’utili...
Read 4 tweets
David Elfstrom Profile picture
3 Nov 20
Wow, this is what I've been advocating for Ontario school boards since August!

The School District of Philadelphia is measuring the outdoor air amount supplied by mechanical #ventilation of every room in every school. THREAD #onted
They use 15 CFM per person of outdoor air as the threshold.

Technically, ASHRAE Standard 62.1 is 10 CFM/person plus 0.12 CFM/sqft. If there are 18 persons in a 750 sqft room it works out to the same.

You can view the ASHRAE standards from this page: ashrae.org/technical-reso… Recommended healthy air flow in a classroom is 15 CFM per pe
Back in August, I recommended posting a sign on each school room:
Read 14 tweets

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