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David Elfstrom 🍁

@davidelfstrom.bsky.social
11K followers 1.5K following 3.6K 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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David Elfstrom 🍁 @davidelfstrom.bsky.social · 14h
It's kind of seasonal with the worst in Dec-Feb but it would be very much less seasonal if we actually deployed proper measures that would cut off that exponential growth starting on Labour Day, from vaccines to clean air
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 18h
The data is up to September 27 so it's a week in the rearview mirror, and general public is told they can't get COVID & influenza vaccine until October 26, one month after this data.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 20h
Yeah, that coughing and "something going around" discussions is COVID. That nice low summer is over. Toronto's wastewater viral load is showing a consistent upward trend in COVID-19 and nearly zero levels of influenza A & B and RSV. wwater.ca/Ontario/Toro...
Most recent wastewater virus levels for Toronto, with date ending week ending September 27, 2026, showing a clear upward trend in COVID-19 and minimal for influenza and RSV.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 07/10/2026
istock is a Getty company.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 06/10/2026
In Toronto (similar to Chicago) a strong wind usually accompanies rain, turning the umbrella inside out within a few minutes of stepping outside, bending the spine or ripping it apart. Different on the west coast where there are long periods of drizzle without wind.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 04/10/2026
It's an undesire path
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 01/10/2026
FULL SPEED AHEAD!
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 01/10/2026
Another one to add to the list of studies of CR boxes! The supplemental data includes inferred CADR for each unit deployed as well as sound pressure measurements in two classrooms at several distances.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 01/10/2026
Temperature in Vancouver was about 12 C at 9 PM that day. Maybe heating turning on, increasing air exchange through temperature differentials? @mosssphagnum.bsky.social what does the temperature plot show?
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 30/09/2026
By the way, what happened at 9 PM? It starts decaying faster indicating more ventilation.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 30/09/2026
By the time that classroom reached steady state the CO2 levels would likely be in excess of the occupational limit for industrial workers, ignoring all the other contaminants building up in an occupied classroom with 0.13 air changes per hour.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 30/09/2026
Ah! Now that we have the decay curve we can calculate ACH. Given: start 1860; end 1100, ambient 435, duration 6 hours. The air change rate in that classroom is 0.13 air changes per hour. That's what air leakage on a mild day looks like. Completely insufficient by any measure!
ACH = negative natural log of (concentration end minus ambient)/(concentration start minus ambient) all over duration in hours
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 30/09/2026
The shape of that curve looks like near zero outdoor air exchange in a classroom and then the meter was moved outside (otherwise it would follow a decay curve instead of an instant drop)
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Reposted by David Elfstrom 🍁
Save Standard Time @savestandard.bsky.social · 30/09/2026
Congress votes to repeal permanent Daylight Saving Time—less than 9 months after it took effect! On this day in 1974.
Newspaper clipping from the Redlands Daily Facts, California, on September 30, 1974. Headline “Daylight Savings Repeal Voted”.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 30/09/2026
It's also a very narrow sidewalk there on Dundas St W and it smells of urine at that old Giraffe building.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 30/09/2026
AND all-day GO train every 30 minutes to Union and K-W.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 30/09/2026
TWO streetcar routes (504 Dundas and 504 King) plus the 506 is two stops away for both of them.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 29/09/2026
Just Price It happens to work well with emissions too!
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Reposted by David Elfstrom 🍁
Mark Ungrin @mark-ungrin.bsky.social · 28/09/2026
An absolutely damning report on the unnecessary COVID deaths of workers at the Cargill plant in High River, AB, highlighting public health and infection control's mismanagement of the crisis, and failure to engage OHS or follow the precautionary principle. albertapolitics.ca/wp-content/u...
As the evidence marshalled in this report shows, the massive
outbreak associated with Cargill was by no means inevitable. It
occurred because systems designed to protect worker health and
safety failed. And they failed for a number of interrelated reasons.
OHS and AHS Did Not Adopt the
Precautionary Principle
The virus SARS-CoV-2 is spread among humans via aerosol
transmission. The period during which someone with COVID-19
can transmit the virus varies depending on factors such as the
variant and severity of illness, but transmission can occur both
before and after symptom onset. Some infected individuals never
experience illness but still spread the virus to others.
At the beginning of the pandemic, Hinshaw and many other
public health leaders believed that COVID-19 only spread via
large droplets and that asymptomatic transmission was not
occurring. As a result, AHS EPH primarily focused on physical
barriers, physical distancing, hand-washing, and surgical masks as
preventative measures at Cargill.Cargill, AHS, and OHS did not consider the possible range of
aerosol transmission of the virus in a large crowded industrial
work setting and, therefore, did not prioritize — let alone consider
— higher-level control measures such as improved ventilation, air
filtration, and N95 (or equivalent) respirators.
Surgical masks, which were made mandatory at Cargill after April
16, provided inferior protection to workers working eight hours a
day, especially for those working in close quarters with inadequate
ventilation. Sometime between the closure of the facility (April
22) and its reopening (May 4), Alberta OHS came to believe that
tight-fitting, higher-filtration respirators (N95 or equivalent
masks) were required, as demonstrated by the ministerial order
approving KN95 masks (May 3) and OHS officers’ decision to wear
N95 masks during their May 4 inspection. However, the evidence
suggests that this view was not shared by Hinshaw.
Ventilation was not identified as a potential factor in the spread
at Cargill until early May, and even then, there is no evidence that
this pathway was further investigated by AHS or OHS.
Had OHS, AHS, and Cargill adopted the precautionary principle,
which requires taking proactive measures to maximize human
safety before the science about the transmission of a new virus
is known, more aggressive control measures would have been
adopted early on. If improved ventilation, provision of N95 masks
(or cartridge respirators), and other actions had been taken earlier,
hundreds of workers may have been spared from illness.None of the evidence we reviewed showed any communication
or coordination between AHS EPH officials and Alberta OHS at
this time. In response to our freedom of information requests for
email correspondence between the manager for OHS in Calgary
and several AHS officials who were directly involved in the Cargill
response, we were informed by the Government of Alberta’s
access to information that “a thorough search […] did not yield any
records responsive to your request.”195
By April 16, the total number of known confirmed positive cases
had reached approximately 550. At this point, there had only
been one in-person inspection of the plant, that being AHS’ April
7 visit, which resulted in non-binding recommendations. And, as
mentioned, there was no epidemiological analysis of the outbreak
showing the temporal pattern of the spread within the plant and
in the community.
An internal AHS MOH update on April 17 noted that “84% of
new COVID-19 cases [in the province] are in Calgary Zone, ‘most
related to Cargill.”196 By this time, a Cargill worker and union shop
steward had been admitted to an ICU. On April 18, another worker
would need life support care in the ICU. Cargill, AHS, and OHS had
lost control of the outbreak.Echoing Cargill’s response to the union’s April 12 letter, Dreeshen
cautioned workers not to listen to “inflammatory rhetoric” and
appealed to them to instead focus on information from public
health experts:
“…On this call are Alberta’s best medical minds and
they provide Alberta’s government with the best up
to date information on a daily basis and I would just
like to encourage everyone to not get distracted by
misleading noise or inflammatory rhetoric because
any government's primary goal — our core goal — is
to keep our people safe…”
Immediately after the town hall, Dreeshen posted on his social
media: “Directly communicated with [Cargill] workers to reassure
them that their worksite is safe.”217 Internal email messages
among senior officials with the Ministry of Agriculture and
Forestry suggest there was also “a request” to share some “key
messages” about the safety of Cargill’s plant through Hinshaw’s
Twitter account.218
Hours after the town hall, Dr. Nick Etches, acting lead medical
officer of health for the Calgary Zone, wrote to colleagues
requesting assistance with an epidemiological analysis of
the outbreak:
“[Hu] just spoke with [Hinshaw] and she wants us
to answer some questions that will likely require
additional epi support. Essentially we want to
determine the proportion of the Cargill-associated
cases that are due to:
1) Workplace transmission
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 28/09/2026
Wow check out the US Treasury yield. That explains why the Canadian dollar has fallen lately too.
US 10 year Treasury yield chart YTD started at 4.25% and is now 5.27% September 28 2026 mid-day
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 28/09/2026
The lane removal is temporary for the railpath bridge repair. Full details here (PDF): www.toronto.ca/wp-content/u...
Screenshot of PDF: Construction Update #1
West Toronto Railpath Pedestrian Bridge Rehabilitation over Bloor Street West Additional Coating and Repair Work
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 26/09/2026
That's called MGIF Must Get In Front
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 25/09/2026
Definitely NOT gen-AI
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 24/09/2026
We're "good vein" buddies! 🤜🤛
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 23/09/2026
It's that (second) time of the year in Toronto when it makes sense to use as much outdoor air as possible in buildings. At the office. Breathing zone CO2 611 ppm at 10:45 AM
Aranet 4 Home meter on top of a task light reading 611 parts per million of carbon dioxide, 21.8 degrees celsius temperature, 49% relative humidity
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Reposted by David Elfstrom 🍁
Institute of Health Emergencies & Pandemics @uoftpandemics.bsky.social · 22/09/2026
🛡️ As flu season approaches, air filtration remains an important layer of protection against infectious diseases. IHEP member Jeff Siegel @engineering.utoronto.ca) explains how high-efficiency air filtration can help reduce airborne pathogens in shared indoor spaces.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 23/09/2026
This was excellent. Thank you @julieslalonde.bsky.social It really was for everyone. Interactive while private. The video examples helped reinforce the actions using bystanders of all types.
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Julie S. Lalonde @julieslalonde.bsky.social · 17/09/2026
There are many, many reasons to feel powerless these days. Everything feels big & scary. But what if you had the confidence to de-escalate situations - even when it's in public with a bunch of strangers? Give me 1 hour of your time & I'll teach it to you for FREE Register: zoom.us/webinar/regi...
Image of a nighttime cityscape with the words "Stand Up! Bystander intervention training to end street harassment. Happening September 22 from 6-7pm EST. Zoom webinar"
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Glendon Mellow @flyingtrilobite.com · 18/09/2026
Welcome to the #TOphoto Feed! Photography of Toronto, Canada. Currently an open Feed: use hashtag #TOPhoto for your work to appear. 🦝 No AI 🦝 SFW, please 🦝 Use Alt text 📸 Let's see your best photos 📸 Tap the 3 dots at top-right to Like and Pin the Feed 📸 bsky.app/profile/flyi...
An early morning photo of the lyrical white and red Cherry Bridge on Cherry Street, from when Biidaasige Park was under construction. The dark blue water is still and an almost perfect reflection of the bridge can be seen. I am not a professional. iPhone 11 Pro.
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Reposted by David Elfstrom 🍁
George Monbiot @georgemonbiot.bsky.social · 17/09/2026
A macho culture of performative selfishness might start on the roads, through racing, rolling coal, ever bigger SUVs ... But it doesn't end there. If we want to live in a decent country which values human life, we need to change this culture. My column. www.theguardian.com/commentisfre...
theguardian.com
Driving that’s too fast, too dangerous and utterly lawless: why do we tolerate this petro-masculinity? | George Monbiot
In towns and in the countryside, I see 4x4s and pick up trucks driven without care or consicence. It’s a Magafication of transport, says Guardian columnist George Monbiot
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Bean & Sprout's Mom @beansproutsmom.bsky.social · 16/09/2026
The last breath of the aerosol-generating procedure? Scotland's new infection-control guidance and implications for anaesthesia   research-information.bris.ac.uk/en/publicati...
Abstract
In August 2026, Scotland fundamentally changed its infection control guidance regarding how respiratory disease transmission risk is managed - replacing the droplet–airborne dichotomy with the simpler concept of air transmission, and entirely removing the aerosol-generating procedure (AGP) list. This evidence-informed approach is based largely on the findings of clinical aerosol studies undertaken during COVID-19 which demonstrated that many procedures on the existing AGP lists, such as tracheal intubation, generate little or no respiratory aerosol (substantially less than talking or coughing). Removing the AGP list does not mean less protection; it means precautions are based on the likely pathogen, patient's respiratory activity, practitioner exposure and environment. Scotland’s revised guidance offers a timely opportunity to replace the inherited dogmas in international guidelines with rational and evidence-informed respiratory protection before the next respiratory disease pandemic.
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Kanchan @kayehm.bsky.social · 16/09/2026
It's not common for Engineers to take a stand on anything (much to my frustration), that's why this statement from OSPE about Bill 212 and the recent court ruling is so important. ospe.on.ca/advocacy/osp...
ospe.on.ca
OSPE Statement: Where Things Stand on Bill 212 and Toronto's Bike Lanes
Explore the OSPE Statement on Bill 212 and its impact on Toronto's bike lanes and transportation planning.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 15/09/2026
And here they are, last weekend. I'm posting a fan video because the official one from the channel doesn't include the audience sounds. The future is so bright for all of them, but especially Nene.
youtube.com
NENE ROYAL x OZONE BAND LIVE IN NAKAMARKET #PHUKET#12/09/2026
YouTube video by anon saelee
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 15/09/2026
Here's Nene Royal with OZONE performing Welcome to the Jungle by Guns N' Roses when SHE WAS 11 YEARS OLD, and Boon the drummer WAS EIGHT YEARS OLD!
youtube.com
WELCOME TO THE JUNGLE (Guns N' Roses) - Cover by OZONE Kids Band
YouTube video by OZONE Band FC
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Oh The Urbanity! @ohtheurbanity.bsky.social · 14/09/2026
Here’s an angle grinder resistant bike lock on sale at MEC in Canada for $345. This one is on the larger side, good for e-bikes and cargo bikes. Especially ones with larger tubes.
mec.ca
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Reposted by David Elfstrom 🍁
Matt Bors @mattbors.bsky.social · 14/09/2026
It was exactly ten years ago today, on my 33rd birthday, that I posted this comic online.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 13/09/2026
Mike D, 10 days ago! youtu.be/ysCp0E-Fndo
youtu.be
MIKE D So What Cha Want LIVE
YouTube video by MetalNick1
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 13/09/2026
On this day 8 years ago It's a bulldozed wasteland now.
Ontario Place entrance at night. A 3D steel lattice holding a 3D sculpture of the Ontario Place tri-lobed logo is lit by magenta spotlights against a black sky.
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Serenity Now! @cpo10za.bsky.social · 12/09/2026
Great satirical take on the recent AI employee resignation posts.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 11/09/2026
@savestandard.bsky.social here's an article for you 👆
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 11/09/2026
As the western provinces move to permanent Daylight Savings Time, there's real safety and health concerns. It should really have been permanent Standard Time. Here's what school facilities need to consider:
reminetwork.com
Dark edge awaits Alberta and B.C. school days - REMI Network
Alberta and B.C. schools days will begin in the dark this fall and winter after the two provinces transition to permanent daylight saving time on Nov. 1
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 08/09/2026
Exactly. Under Carney, corporations benefit on either side of climate (cause & solutions). Citizens - nope!
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 08/09/2026
The feds have been very much involved in solar for corporations. They have a huge non-refundable 30% tax credit to reduce the cost of solar and batteries, and 100% capital cost allowance in the first year to quickly write them off as an expense.
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Canadian History Ehx @cdnhistoryehx.bsky.social · 07/09/2026
When a Canadian engineer graduates, they are given an iron ring in a ceremony called The Ritual of the Calling of an Engineer. The tradition dates back a century and includes a connection to Rudyard Kipling and a terrible bridge disaster. This is the story. 📸 TranBC 🧵1/8
Six diverse hands forming a circle with fists touching at the center, each wearing a matching silver ring to symbolize unity and solidarity.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 07/09/2026
The abbreviation for Sound Power Level is SWL (the W indicating watts) but it's easy to confuse it with SPL for Sound Pressure Level. Also Lw and Lp respectively.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 07/09/2026
Sound power and sound pressure are both expressed in decibels, but have different base units. IKEA's air cleaner specs have high dB levels but when I had one it was relatively quiet. Turns out they were reporting sound power (the correct way to report) which is numerically higher.
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 07/09/2026
Good article about air cleaner device noise levels (sound pressure vs sound power) by @adamwong.bsky.social
air-fanta.com
The Decibels You Hear May Not Be the Decibels You Think
We often talk about noise in terms of decibels, but few people realize that behind this seemingly simple number lie two entirely different measurement frameworks: sound power level and sound pressure ...
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 07/09/2026
Splendid example of #carchitecture Gibeau Orange Julep in Montreal at dusk as viewed from across its parking lot and 15 lanes of traffic.
View at dusk of a 69-foot tall orange sphere in the background. A car is entering the frame from the left. Two traffic pylons are in front of the car, illuminated by headlights. Bright spotlights illuminate the sphere on its horizontal axis. Taken at GPS 45.496303,-73.655401
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 07/09/2026
That photo is *chefs kiss*
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David Elfstrom 🍁 @davidelfstrom.bsky.social · 07/09/2026
Duralast brand tactile metal plates for pedestrians in Montreal are either Made in France (if square) or Made in USA (if curved).
Two adjacent tactile plates of brand Duralast with a slightly rusty appearance. The left one is slightly curved and says Made in USA while the right one of square shape says Made in France.
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