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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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
Five years ago, November 10 2020 #Toronto was a balmy 21.6 C.
Today? High of 1 C and snowing all day.
Environment Canada daily temperatures for TORONTO CITY weather station November 2020. There was a streak of four days with a high above 19 C.
November 10, 2025 at 3:16 AM
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
That feeling when the wind direction is perfectly aligned with your #bikeTO commute.
Map from intervals.icu showing bicycle route eastbound on College St in Toronto with three wind direction arrows of 9 to 11 km/h and gusts to 28 km/h perfectly aligned to the direction of travel
November 4, 2025 at 1:34 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
Those, and the Secret Railroad (aired on TVO)
Screen capture of animated series The Secret Railroad (circa 1978) showing the main characters of a boy, a man with white beard and tall hat, and a black cat sitting on the top of the hat. They are sitting at a dining table.
October 24, 2025 at 7:10 PM
davidelfstrom.bsky.social
This dapper gentleman #caturday
Tabby cat wearing a red bow neck tie sitting on hind legs staring at something over your left shoulder (it was an insect)
October 18, 2025 at 2:05 PM
davidelfstrom.bsky.social
Happy 10th anniversary to the best political tweet, ever.
Adrian Bott @Cavalorn 'I never thought leopards would eat MY face,' sobs woman who voted for the Leopards Eating People's Faces Party. 4:18 AM · Oct 16, 2015
October 17, 2025 at 11:35 PM
davidelfstrom.bsky.social
The motor vehicle-centric societal thinking observed by @shawnmicallef.bsky.social is demonstrated by @ianwalker.bsky.social et al in "Motonormativity: How social norms hide a major public health hazard" doi.org/10.31234/osf... /1
Statements showing motonormativity in survey responses. Statement 1: If somebody leaves their car in the street and it gets stolen, it's their own fault for leaving it there and the police should be expected to act: Disagree is 87%, agree is 4%. Statement 2: If somebody leaves their belongings in the street and they get stolen, it's their own fault for leaving them there and the police shouldn't be expected to act: Disagree is 37% Agree is 40%.
September 25, 2025 at 2:55 AM
davidelfstrom.bsky.social
Changing the filters on the open source PC fan-based air cleaner. It was still keeping the particulate mass in the bedroom below measurable (0.1 μg/m3) but it's been running for at least 17,000 hours. /1
New 20x20x2 pleated MERV-13 above a dirty one. The dirty one looks like fuzzy dust is covering it. Under that is the partially disassembled PC fan air cleaner, showing the top panel of three 140mm Arctic P40 fans with wires hanging out. 6-fan PC air cleaner made from painted black aluminum next to a 2-drawer filing cabinet. Its about as deep as the filing cabinet (20 inches) and is 20 inches high. The front has a width of about 6 inches.
September 20, 2025 at 11:46 PM
davidelfstrom.bsky.social
Emily May Rose finished panel spray paint illustration, September 14 2025.
A spray paint illustration on an approximately 7-foot tall by 3 foot wide panel. Two raccoons are toasting with beer bottles on top of a brick wall at an open window while a third spray paints a raccoon outline on the brick wall. The panel is on a drop cloth and a small step ladder is off to one side. Behind is the entrance to Northern Contemporary gallery.
September 14, 2025 at 8:21 PM
davidelfstrom.bsky.social
Emily May Rose signs her latest piece outside Northern Contemporary gallery during the Roncesvalles Polish Festival in Toronto
September 14, 2025 at 8:08 PM
davidelfstrom.bsky.social
My daughter and her friends made bracelets and sold them at the street festival yesterday.

Apparently two or three people bought a pair each, and paid the higher amount!
Handwritten sign: 2$ for 1 5$ for 2 Bracelets We only take cash! Thanks for stopping by!
September 14, 2025 at 1:36 PM
davidelfstrom.bsky.social
Find the headphone jack and insert one of these for some peace & quiet. disquiet.com/2019/06/09/d...
Arrangement of four various headphone jacks cut off from the wires
September 11, 2025 at 9:33 PM
davidelfstrom.bsky.social
New road markings have appeared in Toronto using the zig-zag pattern to indicate the passenger loading area in the curb lane adjacent to the streetcar stop. #BikeTO
View from the bicycle looking east on College St approaching Yonge St in Toronto. The right hand lane has zig-zag lines and STOP / TTC (to be read from bottom up) repeated three times, the length of the streetcar. On the curb edge there is a solid line that is offset from the curb by about 1.5 m.
September 11, 2025 at 1:21 AM
davidelfstrom.bsky.social
If you have a large building in Toronto (Postal Code M+), try out the new free automated energy data upload service to help with your building's reporting requirements using ENERGY STAR Portfolio Manager. 1st in Ontario!
www.torontohydro.com/energy-star-...
City buidings with text overlay, "Get automated electricity data uploads to ENERGY STAR® Portfolio Manager®. Energy reporting made easy."
September 3, 2025 at 10:42 PM
davidelfstrom.bsky.social
Brown Bear gets his wings at the CN Tower in Toronto
#Staycation
Well-worn brown teddy bear held up against a backlit transparency of butterfly wings
August 21, 2025 at 11:18 PM
davidelfstrom.bsky.social
#Staycation Toronto report:
There's two groups taking the train downtown: #FanExpoCanada2025 and #JonasBrothers concert. Each have their own unique costumes.
CN Tower viewed from below with blue sky and fluffy clouds
August 21, 2025 at 9:59 PM
davidelfstrom.bsky.social
17% price hike by way of shrinkflation: $10 bag originally had 7 uncooked chicken parmesan, now contains 6. Difference in expiry dates is three months. Manufactured by the sneaky little hobbitses at Grand River Foods, Cambridge, Ontario.
Two empty chicken parmesan bags. Old was $10 for 7x142g chicken cutlets, new is $10 for 6x142g, a 17% price increase. Expiry date of 7 cutlet bag: 2026 January 10. Expiry of 6 cutlet bag: 2026 April 10.
August 9, 2025 at 12:07 PM
davidelfstrom.bsky.social
Midea makes a saddle mount cold climate packaged window heat pump that plugs into a regular outlet just like a window A/C. It's quieter, but a lot more expensive to buy than a window A/C.
Midea Packaged Window Heat Pump specification sheet - operates down to -13 Fahrenheit (-25 Celsius)
August 5, 2025 at 10:03 PM
davidelfstrom.bsky.social
Timeline juxtaposition
Ricky Gervais post of a scowling tabby cat with the caption "Arghh! Shiver me timbers" immediately above Allyson Joule's post: I mistook your scowl for anger, but it was heartache wearing the cruel disguise of absence. I searched for softness, but your eyes were hollow as if love had been erased without ceremony. I broke in silence while you stayed whole.
August 3, 2025 at 7:23 PM
davidelfstrom.bsky.social
They HAD to write in the obvious "surgical masks shall not be used for respiratory protection" because of obstinate IPAC practitioners who claim otherwise.
9.6.3.11 Surgical masks Surgical masks are not considered respirators and shall not be used as respiratory protection by HCWs. Surgical masks may be used by patients who cannot otherwise wear respirators, as determined by the Qualified Person, to provide limited source control to protect HCWs.
August 1, 2025 at 12:02 AM
davidelfstrom.bsky.social
Unhealthy air quality from wildfire smoke over Southern Ontario today #BikeTO
Plot of Toronto West air quality station showing a sharp rise from 10 ug/m3 to 70 ug/m3 of PM2.5, starting the evening of July 30 and into the morning of July 31, 2025. Handheld Temptop Air Quality Meter on a balcony overlooking a Toronto streetcar in the blurred background. The meter is reading 65.8 ug/m3, AQI of 156, and is Poor air quality. Temperature is 21.9 C humidity is 55.8%.
July 31, 2025 at 12:47 PM
davidelfstrom.bsky.social
Protocol is for the driver to hug the right curb, allowing cyclists to pass safely on the left. Like in MTO's driver's handbook diagram 2-12.
Diagram shows vehicle turning right behind a cyclist by entering a pained bike lane (dashed lines, permitted) and hugging the right hand curb.
July 30, 2025 at 10:07 PM