DavidElfstrom

@DavidElfstrom@masto.ai

P.Eng, Energy management, measurement & verification. Born @ 327 ppm CO₂. Safer infrastructure, #ventilation, #IAQ #CorsiRosenthalBox optimization #COVIDisAirborne #COVIDCO2 🇨🇦

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DavidElfstrom, to random

New ASHRAE 62.1-2022
#ventilation addendum adds density correction (PDF: https://ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20errata/standards/62_1_2022_k_20240422.pdf) Most locations will increase.
Calgary #YYC at 1045 m will need 15% more outdoor air than before. Denver CO, 20% more.

DavidElfstrom, to random

Article posted April 10 2024 on MSN (https://www.msn.com/en-us/travel/news/new-study-reveals-surprising-impact-of-hvac-units-on-indoor-air-quality-in-canada-homes/ar-BB1lLyCu) regarding a new study of Indoor Air Quality in Canadian homes sounds interesting!
Except: The institute, the quoted scientists, and the study don't exist. It's completely fabricated by generative AI, with poor sentence structure.

DavidElfstrom,

The author of the MSN article has a LinkedIn profile as being the Digital Marketing and SEO Operations Manager of a company named LinkMill.

There is a single link to a Toronto-based HVAC company named Smile HVAC which is legit but has a very SEO-heavy (near useless) web page.

DavidElfstrom,

Feel free to report this article (https://www.msn.com/en-us/travel/news/new-study-reveals-surprising-impact-of-hvac-units-on-indoor-air-quality-in-canada-homes/ar-BB1lLyCu) by selecting the three dots on the left and "Report an Issue". Check the appropriate boxes.

DavidElfstrom, to random

#Ventilation & CO2 Addendum ab (PDF: https://www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/62_1_2022_ab_20231031.pdf ) to ASHRAE Std 62.1-2022 (Ventilation & Acceptable Indoor Air Quality) provides maximum CO2 levels for the minimum ventilation requirements.
Example: 600ppm + Outdoor (420ppm)= 1020 ppm max for classroom

This is for code MINUMUM ventilation, which in most cases have not changed for many years. It's not for airborne disease control.

DavidElfstrom, to random

This paper reports transmission occurring after 4 hours of vacancy in a room with 6 ACH ventilation measured at some undisclosed time before the outbreak.

24 air changes (6 ACH x 4 h) is a 99.999999996% reduction. Highly improbable to infect. More likely the actual ventilation rate was much lower at the time. https://www.ajicjournal.org/article/S0196-6553(24)00162-7/abstract

DavidElfstrom,

There really needed to be some multidisciplinary input to this report, and not accept "6 ACH" at face value. Inspect the equipment. Do a test with tracer aerosols. Anything.

PieterPeach, (edited ) to llm
@PieterPeach@mastodon.social avatar

While driving, my iPhone not only read aloud a text message, but also accurately described an attached photo.
That was unexpected

DavidElfstrom,

@PieterPeach How do you drive your iPhone when it doesn't have any wheels 😅

DavidElfstrom, to random

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%!

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. /1

DavidElfstrom,

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.

HEPA-class filters aren't the optimal solution, unless that's all you are offering as a product. Instead, design for a system using a ISO 16890 or ASHRAE 52.2 rated filter, say ePM1 > 60% or MERV-13. These filters have far less restriction to airflow than HEPA filters. /2

DavidElfstrom,

A portable air cleaner designed to use a less expensive general ventilation filter can move substantially more air through it to achieve a greater CADR at low noise, and with lower electrical power consumption than a unit based on a HEPA filter.

And in case you are wondering, good quality general ventilation filters will remove health-damaging ultrafine submicron particles too, that optical particle counters can't even detect. /3

DavidElfstrom,

To recap, for in-room air cleaners, a HEPA-class filter IS NOT NEEDED. What matters is the combination of filtration, fit, and airflow, to maximize the Clean Air Delivery Rate for a target particle type and size, verified by an independent laboratory test to an industry standard, with acceptable noise parameters.

Everything else is just marketing. /4

DavidElfstrom,

This is why it doesn't matter if some brand of air purifiers aren't a certain class of "HEPA" by a particular rating system, other than for faithful labeling & consumer trust (looking at you, Levoit). All that matters is the independent CADR test (looking at you, Austin Air). /5

DavidElfstrom, to random

This passage should be cut out and stapled to the front of every report from a school board that says it wasn't possible to upgrade filters to MERV-13. https://asteriskmag.com/issues/05/lies-damned-lies-and-manometer-readings A wide-ranging look on the state of the (mostly residential) HVAC sector.

DavidElfstrom, to random

Hospital acquired chicken pox in child due to unvaccinated health care worker transmitting from one patient to another https://www.cambridge.org/core/journals/epidemiology-and-infection/article/case-report-hospitalacquired-chickenpox-in-a-healthcare-setting/CAD9FE221545EBC0DC3B5BBE5A2E3CBC

DavidElfstrom, to random

Air cleaning is simple. It's a filter and a fan. DIY air cleaners are an example. But products are designed to lock you into a proprietary system to generate ongoing profit from early replacement of overpriced filters, generating unnecessary waste. https://hackaday.com/2024/01/26/hacking-a-xiaomi-air-purifiers-filter-drm-to-extend-its-lifespan/

DavidElfstrom, to random

Nukit has open sourced a DIY air purifier frame that can be made with a laser cutter. Quie, like other similar PC fan array designs. I tested it with MERV-13 and Arctic P14 fans: Dust/Bioaerosol CADR of ~290 CFM, Smoke CADR of ~210 CFM, and draws just 8 watts https://github.com/opennukit/Nukit-Open-Air-Purifier/

DavidElfstrom, to random

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 design, certifiable product, efficient, repairable using commodity filters and commodity components. Assembled and distributed by not-for-profit community-based social enterprise.

No more lock-in to proprietary filters, but verified commodity filtration performance for confidence and safety.

DavidElfstrom,

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)

/2

DavidElfstrom,

People also don't want to operate the donated duct taped solution due to appearance and noise. (study: https://mdpi.com/2073-4433/14/12/1734)

That's why it's important to have an open-source repairable product design assembled and distributed by non-profit community-based enterprise. /3

mastodonmigration, (edited ) to random
@mastodonmigration@mastodon.online avatar

So apparently Tesla cars are falling apart. Tesla refuses to recall them and fix critical safety problems. Tesla has been lying to safety agencies. And now two Senators are joining in and demanding the company recall their dangerous product.

https://www.reuters.com/business/autos-transportation/two-us-senators-call-tesla-recalls-after-reuters-investigation-2023-12-27/

DavidElfstrom,

@mastodonmigration Same advice applies to billionaire pet project spacecraft and submersibles

DavidElfstrom, to random

Doing the job of correcting public health messaging for three years

DavidElfstrom, to Toronto

From 2016.
T-shirt for subway riders. Creator unknown.

DavidElfstrom, to random

"I feel like somebunny's watching me"

DavidElfstrom, to random

perched on the mat

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