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David Elfstrom Profile picture
@DavidElfstrom
Apr 10, 2021 • 10 tweets • 4 min read • Read on X
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LISTEN as highly influential Prof John Conly (upper left) of UCalgary, AHS CV19 sci advisory grp, Public Health Agency Canada, Chair WHO Infection Prevention & Control R&D Expert Grp. opposes N95 wearing citing acne harm vs @DFisman & @kprather88 precautionary principle. /1
"there's been decreased O2 concentrations in pregnant women" yeah, well here's the reference from one of his publications, dissected in fine form by @caruzycki /2
Here's an example of Prof Conly's influence by the dedicated @jmcrookston /3
What would a dermatologist prefer, acne or COVID-19? Let's find out! /4
Because of Prof. Conly's influence, public health agencies around the world continue to double down on contact and droplet. Public Health Ontario: /5 January 29, 2021: Droplet and Contact Precautions continue to be recommended for the routine care of patients with suspected or confirmed COVID‑19.
February 19, 2021 Directive 5 FAQ from Ontario Ministry of Health & LTC:

Droplet & Contact precautions, and conserve PPE.

Conserve PPE, despite ample supplies. One year into the pandemic. It's egregious. /6 Image
Here's what the CDC and NIOSH have to say about the differences between Surgical Masks and N95 Respirators. /7
(image adapted from ) cdc.gov/niosh/npptl/pd…
Image
The presentations by Prather and Fisman make an excellent summary of how the wide variance in respiratory aerosols produced by people can explain the high dispersion factor of COVID-19. Highly recommended to view the 60 minute session in its entirety /8 ucalgary.yuja.com/V/Video?v=3323…
Dr. Conly is the primary & corresponding author of WHO commentary article stating "SARS-CoV-2 not airborne to any significant extent, respirators offer no advantage & may result in unintended harms" same as he said in the video above /9 aricjournal.biomedcentral.com/articles/10.11…
Image
Regarding the poor experimental design leading Conly to claim N95 leads to "decreased O2 concentrations in pregnant women", thread is archived here:

OF COURSE you can't get much air when you're breathing through such a restricted contraption. /10
Conor Ruzycki: They use a rigid Hans-Rudolph mask with the outlet covered by a snipped out circle of N95 mask material to simulate an N95. What's the problem with this? Well, with a normal N95 you breathe across the entire surface of the mask (or most of it, anyway), something that has an area of 150 square cm. The cross sectional area of this "N95-equivalent" is much smaller - lets call it 30 square cm.

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More from @DavidElfstrom

David Elfstrom Profile picture
Mar 28
Three years ago on this day ASHRAE stated that Airborne transmission of SARS-CoV-2 is significant.

Today, WHO finally released a model () of #CovidIsAirborne risk by experts in the field. /1 iris.who.int/handle/10665/3…

Landing page for the WHO document titled: Indoor airborne risk assessment in the context of SARS-CoV-2: description of airborne transmission mechanism and method to develop a new standardized model for risk assessment
Four years ago on this day WHO said : "FACT: #COVID is NOT airborne."

Today, WHO finally released a model () of #CovidIsAirborne risk by experts in the field that warned of airborne even earlier, but were shut out. /2
iris.who.int/handle/10665/3…
WHO Tweet March 28, 2020 FACT: #COVID19 is NOT airborne. The #coronavirus is mainly transmitted through droplets generated when an infected person coughs, sneezes or speaks. To protect yourself: -keep 1m distance from others -disinfect surfaces frequently -wash/rub your hands -avoid touching your eyes / nose / mouth Cover page of Indoor airborne risk assessment in the context of SARS-CoV-2
This document has been a long time coming. As described by @jljcolorado, Lidia Morawska, co-chair of the group that published the new WHO airborne model, was previously cut off by John Conly when making the case that #COVIDisAirborne to WHO. /3
Acknowledgements: WHO ARIA Technical Advisory Group: First name: Lidia Morawska (Co-Chair) (Queensland University of Technology, Australia) (many other names) John Conly (University of Calgary, Canada)
Read 4 tweets
David Elfstrom Profile picture
Feb 23
Air purifier manufacturers say HEPA should always be the filter of choice, and their product's proprietary filter delivers. Which HEPA? ISO 35H at 99.95% or ISO 40H at 99.99%? Why not ISO 50U? That's 10x better at 99.999%. Why stop there? Go for ISO 70U at 99.99999%! /1
The answer is, single-pass filtration efficiency DOESN'T MATTER except in specific cases like Powered Air Purifying Respirators (PAPR), clean rooms, operating theaters, or nuclear laboratory exhaust—HEPA's original purpose. /2
For portable/in-room air cleaners, all that matters is the Clean Air Delivery Rate (CADR) for a target particle size and type, within acceptable for sound power and frequency characteristics for the people in the room. /3
Read 13 tweets
David Elfstrom Profile picture
Jan 3
Four years into this and we can't keep duct-taping in-room filter solutions for clean air. It's just filter(s) and a fan. We need open-source, optimized design, certifiable product, efficient, repairable using commodity filters and commodity components. /1
We need air cleaners assembled and distributed by not-for-profit community-based social enterprise. No more lock-in to proprietary filters. Verified replacement commodity filtration performance for safety. /2
Low income with donated CR boxes will pay over time in electrical costs for the duct-taped solution for clean air.
Power utilization for Smoke CADR, same filters:
Conventional CR Box: 4 CADR/W. (77 W)
PC fan array air cleaner: 24 CADR/W. (8 W)
/3
Read 4 tweets
David Elfstrom Profile picture
Aug 28, 2023
1/ Levoit Core 400S versus Austin Air HM400 in a challenge to see which portable air cleaner removes submicron salt particle aerosols the fastest! Which do you think will win, and by how much? Poll in next tweet below... A large indoor tent with taped seams on a concrete floor is shown. On the left is a bench with instruments. A webcam is mounted on the top of a chair facing the instruments. In the middle are two air purifiers: The cylindrical Levoit Core 400S and the larger boxy Austin Air HM400. In the back right corner is a circular floor fan pointed diagonally upward into the middle. At the front right is a chair holding what looks like a tiny pitcher with a spout. A long thin clear plastic tube is connected to the side of this device, and exits the frame. Power cords are on the floor.
2/ Which has a higher CADR (Clean Air Delivery Rate):
Levoit Core 400S, or Austin Air HM400?
See if you can find the manufacturer's claims for both, and then come back and vote:
[sarcasm] Not only is the Austin Air bigger and far heavier, it also draws way more power, is much louder, and more expensive. It couldn't possibly be *worse* than the Levoit, right? Right?
Read 13 tweets
David Elfstrom Profile picture
Jun 12, 2023
When to change the filter on DIY #CorsiRosenthalBox? Holder et al (onlinelibrary.wiley.com/doi/10.1111/in…) showed that performance degradation depends on contaminant: Dust reduces airflow. Smoke kills electrostatic properties. @JimRosenthal4 @joeyfox85 @CorsIAQ Table for MERV 13 single-fi...
@JimRosenthal4 @joeyfox85 @CorsIAQ Note the test substance for the CADR PM2.5 performance measurement was simulated wildfire smoke.
The same would likely apply to a commercial HEPA air cleaner. Monitor for clearing time for a fixed release of contaminant with a simple PM meter.
Read 6 tweets
David Elfstrom Profile picture
Apr 12, 2023
When an IAQ report for an elementary school states the acceptable industry CO2 guideline is 700 ppm above ambient, or 1200 ppm, ask why the professional is using Std 62.1-2016 Informative Appendix D that was DELETED in 2018 because of misuse and outdated 1950's data.
@O_S_P_E 's calculator will give a target steady state CO2 value based on Standard 62.1 minimum acceptable outdoor air ventilation rates. Hint: It's not 1200 ppm for an elementary classroom. Link: https://t.co/V1DwupuJ3xospe-calc.herokuapp.com
Key phrases identifying that the deleted Informative Appendix D was used:
-Target of 700 ppm CO2 above ambient
-ambient is 300-500 ppm
-majority of occupants be satisfied with respect to human bioeffluents
-uses 1.2 MET, 15 CFM (7.5 L/s), 0.31 L/min
Read 4 tweets

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