David Elfstrom 🍁
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davidelfstrom.bsky.social
David Elfstrom 🍁
@davidelfstrom.bsky.social
11K followers 1.4K following 3.1K posts
P.Eng, Energy management, measurement & verification. Toronto, Canada. Born 327ppm CO2. Climate Action & electrification; Safer infrastructure; cycling; air filtration & ventilation
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Reposted by David Elfstrom 🍁
davidelfstrom.bsky.social
This is literally the method they used for aerosol droplet sample collection.
Cough and continuous speech samples were collected in sealable, transparent polyethylene bags (~ 27 × 27 cm and 18 × 19 cm, respectively) which were opened wide enough to accommodate the mouth and lower face and held in place at a distance < 2–4 cm to ensure adequate sample collection. Two to 5 mL of DMEM + was added to the bags, followed by thorough mixing to ensure the contents of the bags, including the condensation on the inside surfaces from the continuous speech samples and retained air would have contact with the culture media, prior to closing and sealing, given some air was expelled with sealing. Man coughing into a medium size PC Brand polyethylene bag, held at the stated 2-4 cm distance away from the face, as described in what can be described as having a complete lack of understanding of fluid mechanics
November 11, 2025 at 12:55 AM
davidelfstrom.bsky.social
Meanwhile this is how respiratory aerosols are captured by infectious disease researchers who understand physics.
Diagram of G-II exhaled breath bioaerosol collection system. It's a cone with the wide end over a person's face, inside a tent with controlled humidity. The funnel draws air into equipment including an impactor and then is filtered with a HEPA filter and returned to the room. (U = upstream sampling location; D = downstream sampling location; T = temperature sensor; M = Magnehelic R pressure gauge; RH/T = relative humidity and temperature sensor; V = voltage controller; F = flow controller). Virus shedding by participants was measured using the Gesundheit II machine developed by the University of Maryalnd's Dr. Don Milton Credit University of Maryland School of Public Health
November 11, 2025 at 1:02 AM
davidelfstrom.bsky.social
This is literally the method they used for aerosol droplet sample collection.
Cough and continuous speech samples were collected in sealable, transparent polyethylene bags (~ 27 × 27 cm and 18 × 19 cm, respectively) which were opened wide enough to accommodate the mouth and lower face and held in place at a distance < 2–4 cm to ensure adequate sample collection. Two to 5 mL of DMEM + was added to the bags, followed by thorough mixing to ensure the contents of the bags, including the condensation on the inside surfaces from the continuous speech samples and retained air would have contact with the culture media, prior to closing and sealing, given some air was expelled with sealing. Man coughing into a medium size PC Brand polyethylene bag, held at the stated 2-4 cm distance away from the face, as described in what can be described as having a complete lack of understanding of fluid mechanics
November 11, 2025 at 12:55 AM
davidelfstrom.bsky.social
or No Name or PC Brand polyethylene bags, because hey it's Canadian research
November 11, 2025 at 12:32 AM
davidelfstrom.bsky.social
Oh wait again. That was the flight. The previous United flight on that number and route was Friday and it went to 34,000 ft and 430 kts, as is typical.
November 10, 2025 at 3:37 AM
davidelfstrom.bsky.social
Oh, the flight above was today. The Reddit post seems to indicate it was yesterday, which explains why the flight tracker link above is only 6075 ft (!!) rather than 8000 ft.
November 10, 2025 at 3:27 AM
davidelfstrom.bsky.social
Five years ago it was 21 C!
November 10, 2025 at 3:18 AM
davidelfstrom.bsky.social
Here is the flight www.flightaware.com/live/flight/...
Flight Track Log ✈ UAL2320 09-Nov-2025 (KEWR-KSAV) - FlightAware
Best Flight Tracker: Live Tracking Maps, Flight Status, and Airport Delays for airline flights, private/GA flights, and airports.
www.flightaware.com
November 10, 2025 at 2:36 AM
davidelfstrom.bsky.social
Yep bsky.app/profile/davi...
davidelfstrom.bsky.social David Elfstrom 🍁 @davidelfstrom.bsky.social · Nov 20
Stunning cover design by Beverley McDonald, UNEP
Report available from: www.unep.org/resources/em...
Cover of the report: Emissions Gap Report 2023: Broken Record – Temperatures hit new highs, yet world fails to cut emissions (again). By: UN environment program Deep blue background with bright coloured concentric circles. The inner circles are smooth and cool colours while the outer circles are bumpy and hotter colours. A record player needle head over top suggests this is an overhead view of a turntable and the circles are the grooves in an album as well as being temperature records.
November 5, 2025 at 1:08 AM
davidelfstrom.bsky.social
Thank you! Followed.
November 4, 2025 at 11:23 PM
davidelfstrom.bsky.social
Arg! The direct headwind component on the return trip was about 15 km/h:
cos(30°) * 18 km/h. Nice temperature though, clear sky and 13°C.
Map from intervals.icu showing a westbound commute along College St in Toronto showing headwinds at a 30 degree angle, of 18 km/h with gusts to 37 km/h
November 4, 2025 at 10:54 PM
davidelfstrom.bsky.social
Neighbours just shot off fireworks

A good game indeed
November 2, 2025 at 4:32 AM
davidelfstrom.bsky.social
I would hate to be a car — period.
November 1, 2025 at 9:48 PM
davidelfstrom.bsky.social
Reminds me of the old "Internet Explorer is slow" joke
Firefox, Internet Explorer, and Safari browsers responding to Chrome's questions (What are we? Browsers! What do we want? Fast Internet!) except IE is silent. Then Chrome asks When do we want it? And IE finally says "Browsers!"
October 29, 2025 at 2:50 PM
davidelfstrom.bsky.social
6-7
October 25, 2025 at 11:05 PM