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"
Was "late model Honda Accord".
Unknown: Recirc setting? Fan speed setting? Actual model (so we can measure air flow), cabin air filter type? Even so, was only 15 minutes. However filters may have caught larger particles during the drive.

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More from @DavidElfstrom

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
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
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
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
2 Nov 20
I'm already seeing 6 Air Changes per Hour as a blanket number. However this depends on volume, or rather, the ceiling height vs floor area and occupancy. A rough guide might be:
12 ACH small volume (vehicles)
6 ACH average (office, classroom)
3 ACH large vol (arena, warehouse)
Houses and apartments are quite a bit different: ASHRAE has an entirely different standard just for residential #ventilation! Easier to think of per person amounts.

Try for 30 CFM per person for COVID-19 but no less than ASHRAE 62.1 Table 4-1a in ASHRAE 62.1-2019
Drat. I meant no less than ASHRAE 62.2

By the way, the relevant pandemic ASHRAE standards are available for free to view on their website, which I greatly appreciate. <glares at CSA>
Read 5 tweets
20 Sep 20
BREAKING
CDC changes COVID-19 guidance, airborne is primary way the virus spreads, touching surfaces is NOT the main way. #Ventilation is important, as it goes beyond 6 ft and remains suspended in the air.
H/T @jljcolorado & @jmcrookston Comparison of text from archive.org showing difference betwe
Canada, you need to revise your guidance to be in line with science, known since February. Add breathing and inhalation. Minimize surface transmission. Add poorly ventilated spaces as risk factor, remains in the air and travels greater than 2m indoors.
canada.ca/en/public-heal…
One-stop must-read by the top aerosol scientists:
FAQs on Protecting Yourself from COVID-19 Aerosol Transmission
This document is frequently updated.
Shortcut: tinyurl.com/FAQ-aerosols
Read 8 tweets

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