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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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.
"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
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…
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
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
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>
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
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