Prof. Jose-Luis Jimenez Profile picture
Jun 25, 2021 32 tweets 14 min read Read on X
1/ NEW CAMPAIGN: I'M HELPING @zerocovidthai (with generous support from @AranetloT) to DONATE CO2 METERS to SOUTHEAST ASIA

COVID-19 is mostly transmitted through the air, by breathing in infectious aerosols, in close proximity or in shared room air (thelancet.com/journals/lance…) Image
2/ For that reason, this is an indoor-dominated pandemic. It is much easier to be infected indoors than outdoors (academic.oup.com/jid/article/22…).

The best infection prevention strategy is do everything that you can outdoors
3/ But we have to go indoors at times.

Measuring the virus in the air is difficult, slow, and expensive.

CO2 indoors marks the presence of exhaled air, and serves as a proxy for the virus (cartoon from @numeroteca)

#covidCO2 Image
4/ This article in @elpaisinenglish provides a good overview of how measuring CO2 works and what we can learn from it:

english.elpais.com/usa/2021-03-29…
5/ There are multiple research papers on this, e.g. ours: pubs.acs.org/doi/10.1021/ac…
onlinelibrary.wiley.com/doi/abs/10.103…
medrxiv.org/content/10.110…

We explain this also in Section 9 of our Scientist’s FAQs: tinyurl.com/faqs-aerosol Image
6/ So how does it work?

Outdoors there are ~ 400 parts-per-million (ppm) of CO2. Humans exhale ~40000.

So CO2 in indoor air increases, especially with poor ventilation. Often it reaches 2000, 3000, 5000, and we have seen up to 7000 ppm.
7/ If CO2 indoors is 800 ppm, 1% of the air is “second-hand” and has been in someone’s lungs before. If it is 2400, that’s 5%. That is quite risky, if an infected person is present. Image
8/ We recommend keeping CO2 indoors below 700 ppm at all times during pandemic, & below 1000 if the location has good filtration (filters remove virus but not CO2)

Measuring CO2 --> are we ventilating enough? (or too much?. Especially useful for natural ventilation (windows) Image
9/ CO2 serves as indicator of RELATIVE risk anywhere (e.g. a choir rehearsal with half the CO2 enhancement is twice as safe as original; same for library)

- ABSOLUTE risk at the same CO2 is much higher at choir rehearsal than library

(More details: pubs.acs.org/doi/10.1021/ac…)
10/ Which factors increase risk? (for same CO2)

- Strong vocalization (more virus out)
- No masking (more virus out & in)
- Breathed volume (e.g. exercise, more virus inhaled)
- Event duration (more inhaled)
- Infection rate in population (higher chance of infected present)
11/ You can estimate the amount of CO2 present in a given activity with our COVID Aerosol Transmission Estimator:

tinyurl.com/covid-estimator

If you do the measurements for an activity, adjust ventilation rate till you match observed CO2 *average*
12/ Many national and international bodies recognize the usefulness of CO2 and have issued recommendations for indoor levels. For example the US CDC recommends portable CO2 meters to monitor natural ventilation:
cdc.gov/coronavirus/20… Image
13/ The Belgian government recently required CO2 meters in high-risk locations (bars, restaurants, gyms):

14/ The Science Task Force in Switzerland has published similar recommendations, as have multiple other countries:

15/ The Spanish Minister of Science tweeted that "the most important thing to do now is to ventilate and measure CO2":

16/ Measuring CO2 is not just useful during pandemic. After, it should be kept below 1000 ppm at all times. Because there is significant cognitive decline above that level, and there are other health issues due to indoor contaminants.
17/ This was already a law in some countries before the pandemic (mdpi.com/2073-4433/9/5/…)

ncbi.nlm.nih.gov/pmc/articles/P… Image
18/ Fortunately, there are now affordable, fast, and reliable CO2 monitors.

They are based on non-dispersive infrared (NDIR).

AVOID other CO2 meters (even though they can be cheaper), they don’t work well or at all.
19/ @EJimenez_UCLM has led the testing of many NDIR meters and has some recommendations of those that work well, as well as the features we recommend.

bit.ly/monitorsCO2

(Testing is done in Spain, but many of those are available globally)
20/ And it should always be displayed publicly in all spaces where we share the air Image
21/ This is part of a paradigm shift in the importance of indoor ventilation for reducing respiratory infections, which has been ignored everywhere for a century:

science.sciencemag.org/content/372/65…
22/ For example, shared cars are especially dangerous (if we don't pay attention), because they have a small volume, and if windows are not open and outdoor ventilation is off, exhaled breath accumulates very quickly. Image
23/ And this is an explanation of the dynamics of shared cars from @elpaisinenglish, but it is applicable to other indoor spaces. Image
24/ We have previously donated 120 CO2 meters to Spain and Latin America (with donations from many of you through GoFundMe, @citlanx, @AranetIoT @EspanaAranet, and myself).



25/ Thanks to the initiative of @zerocovidthai, and with gracious support and donation from @AranetIoT / @SAFTehnika, we are starting a new campaign for Southeast Asia.
26/ We can accept requests from Thailand, Philippines, Indonesia, Malaysia, Vietnam, Singapore.

Not sure whether we can send donations to Cambodia, Myanmar, Laos, East Timor, Brunei. (You can apply from those countries, but we’ll have to see whether shipping there is feasible)
27/ We will distribute #Aranet4 meters, which work well, as verified in multiple tests by scientists, e.g. by @EJimenez_UCLM (tweet above), or this testing by @HuffmanLab_DU:

28/ The Aranet4 meters are small and discrete, and they save the data for several days. So you can just have them in a pocket or purse, and look at the data at the end of the day or after several days. This is an example of my visit to a dental office:

29/ We would like to donate the CO2 meters to scientists, health care workers, activist, journalists & others who can measure in multiple places and make the information public, e.g. in Twitter or Instagram using the #covidCO2 tag.
30/ We normally have 5-10 times more requests than available meters to donate, so a commitment to share the information (and the meter) is important.
31/ 35 of the meters are donated by @AranetIoT, but we are raising funds to extend the campaign to another 35 meters (purchased w/ large discount). If you can, please donate at: gofund.me/2e169c20

All the funds will be used to buy CO2 meters (minus a ~1% fee from GoFundMe)
32/ If you want to request a meter, please enter your information in English in this form. We will select & announce the winners in Twitter/Instagram. There are ++ more requests than meters, so pls explain well how you would use and share the meter.

forms.gle/ukBuNcM5Xbjmoo…

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More from @jljcolorado

May 26
1/ Survey of CO2 indoors during trip

CO2 (above ~400 ppm outdoors) indicates the amount of exhaled air (& virus) trapped in a space

Also per recent scientific results by @ukhadds, CO2 helps SARS-CoV stay infectious in air much longer

@united flight boarding, pretty terrible! Image
2/ This is the trip so far:

-Low outdoors
-Pretty high ~2000 in @RideRTD bus to airport
- ok ~800 at @DENAirport, except restroom ~1500. Not sure why restrooms at this airport are so often poorly ventilated
- Then boarding on @united, ventilation OFF, so huge increase till ON Image
3/ For details of the recent results on how and why CO2 makes SARS-CoV-2 stay infectious much longer in the air, see this recent thread by @ukhadds

Read 9 tweets
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
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
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
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
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

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