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Prof. Jose-Luis Jimenez Profile picture
@jljcolorado
Sep 24, 2020 • 5 tweets • 4 min read • Read on X
A5(1) It is clear that ventilation reduces transmission
- Ballistic droplets & close proximity aerosols not affected by vent.
- Only shared-room-air aerosol transmission impacted by ventilation. This is a major pathway of transmission

#LeapsChat @leapsmag
A5(2) "ventilation" here = remove virus from the air
- A fan that moves air around is not ventilation

- 2 things:
(a) expel indoor air outdoors, bring clean air indoors (open windows, or through mechanical HVAC systems)

(Details: sciencedirect.com/science/articl…)

#LeapsChat @leapsmag
A5(3) Second thing to do:

(b) Filtration: either through HVAC systems (MERV 13 if possible), or through portable HEPA filters, or through cheaper fan-filters.

Extensive details: tinyurl.com/FAQ-aerosols

#LeapsChat @leapsmag Image
A5(4) There are other types of air cleaners.

- UV is good, but needs professional installation for several reasons (see 9.8 in tinyurl.com/faqs-aerosol)

#LeapsChat @leapsmag
A5(5) We don't recommend other types of air cleaners. Stick w/ ventilation w/ outdoor air, filtration if needed, and UV is really needed.

More details:

#LeapsChat @leapsmag

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More from @jljcolorado

Prof. Jose-Luis Jimenez Profile picture
May 8
1/ "After four years of fighting about it, @WHO has finally proclaimed that viruses, including the SARS-CoV-2 virus that causes COVID, can be spread through the air"



By @maggiemfoxscientificamerican.com/article/a-figh…
2/ "It took four years to get here because some leaders in public health, medicine and science clung too tightly to precision and semantics"

"One particular moment of shame came on March 28, 2020, when WHO tweeted: “FACT: #COVID19 is NOT airborne.”

3/ "Words matter. When people heard that COVID might spread on surfaces, they wasted time wiping down groceries. People who misunderstood airborne spread needlessly wore masks on outdoor walks and veered off sidewalks to avoid their neighbors."
Read 7 tweets
Prof. Jose-Luis Jimenez Profile picture
Apr 18
1/ @WHO has published a report on updated terminology for disease transmission

I've seen some debate about it. My take:

- Terminology itself is ok. Big progress
- But no recommendations of how to protect!

Report:

Press release: who.int/publications/m…
who.int/news/item/18-0…
2/ The report was likely the result of intense pressure on @WHO during the pandemic:

- They denied that #COVIDIsAirborne on March 2020
- They finally accepted it 2 years later

nature.com/articles/d4158…
@WHO 3/ To their credit, @WHO did invite some of their critics to be part of the committee.

What was the terminology before. In medical circles:

- droplet transmission: if it happened in close proximity, or if particles were > 5 microns

- airborne transmission: if it happened far
Read 34 tweets
Prof. Jose-Luis Jimenez Profile picture
Mar 28
1/ New paper in @ScienceMagazine: "Mandating Indoor Air Quality for Public Buildings"

Explaining current status of indoor air quality standards (in short: bad or non-existent), the huge health benefits that would arise from them & proposing a path forward
science.org/doi/10.1126/sc…
Image
2/ "People living in urban & industrialized societies, which are expanding globally, spend more than 90% of time indoors, breathing indoor air (IA)."

"Most countries do NOT have legislated indoor air quality (IAQ) performance standards for public spaces"

science.org/doi/10.1126/sc…
3/ "Few building codes address operation, maintenance, and retrofitting, and most do NOT focus on airborne disease transmission."

"We propose that Indoor Air Quality (IAQ) standards be mandatory for public spaces"

science.org/doi/10.1126/sc…
Read 14 tweets
Prof. Jose-Luis Jimenez Profile picture
Oct 4, 2023
1/ Checking the ventilation by measuring CO2 as I travel to the #AAAR2023 conference

@RideRTD bus to Denver airport. Bus route had started 3 min before I got in, already 1500 ppm

Typical of these @RideRTD buses, poor ventilation Image
2/ Not getting any better as time passes in the @rideRTD bus to the airport...

7% of the air is being re-breathed, it has already been in someone else lungs when each of us breathe it. Image
@RideRTD 3/ Given the often poor-to-mediocre ventilation in US transportation systems, I wear N95 masks (not KN95, less good)

In this case @3M VFlex, which I tested at 99.99% filtration for myself

It also stays sealed when I talk, doesn't distort my speech (& add to my Spanish accent) Image
Read 14 tweets
Prof. Jose-Luis Jimenez Profile picture
Oct 2, 2023
1/ Video de mi presentación sobre "Transmisión de enfermedades por el aire: cómo funciona, por qué se malentendió, y cómo reducirla"

como parte de la presentación del libro de ventilación de @aireamos

2/ Las diapositivas se pueden bajar de este enlace.

(Son de una charla más larga así que tienen más detalles, pero están todas las de la presentación de @Aireamos)

drive.google.com/file/d/1Bs0RRG…
@aireamos 3/ Miguel Ángel Campano @MA_Campano y @Aireamos han sido los motores del libro de ventilación:

Read 4 tweets
Prof. Jose-Luis Jimenez Profile picture
Sep 1, 2023
1/ Measuring CO2 indoors in a 10 day trip from US to Europe & back

Bus @RideRTD to Denver airport, poorly ventilated as usual.

We have not left town yet! In previous trips it kept increasing, we'll see this time. Image
2/ For background on what CO2 indoors indicates and more details, see

TLDR:
- We exhale 40000 ppm CO2
- Outdoors: 420
- Each 400 extra ppm indoors = 1% extra rebreathed air
- CO2 makes us dumber, indicator of virus & pollutants. Does not capture filteringdocs.google.com/document/d/e/2…
3/ Or by reducing recirculation. Some recirculation is ok if well-filtered, saves energy.

Energy-recovery ventilators allow ventilating well with limited energy use.

Read 18 tweets

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