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New post: Nine observations from three and a half years of carbon dioxide monitoring. #COVIDIsNotOver #COVIDIsAirborne

https://grieve-smith.com/ftn/2026/03/nine-observations-from-carbon-dioxide-monitoring/

Nine observations from carbon dioxide monitoring

Introduction In the first year of the COVID-19 pandemic I learned that we can estimate our level of risk by checking the concentration of carbon dioxide in the air, because when infected people breathe out virus aerosols, they also breathe out CO2. I recently wrote about some limitations on this

Commentary by A. Grieve-Smith

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Violet Madder Mar 22

@grvsmth

Wow.

I've been wanting to do some of this myself.

I had a bad feeling about Amtrak, it just FEELS stuffy on those and that's just awful when it's one of the only modes of transportation that otherwise makes any damn sense and yet it's not safe to use the thing, on top of it running so slow because capitalism ruined it and we're not allowed to have nice things.

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Angus Andrea Grieve-Smith Mar 22

@violetmadder Thank you! I think Amtrak is safe, relative to buses, planes and driving. The times I've gotten sick since 2015 haven't been within a few weeks of my Amtrak trips.

It helps to eat in the cafe car, and if possible, find relatively uncrowded cars and schedule your travel for times when transmission rates are low.

Of course, Amtrak management should work to improve the ventilation! All the cars I tested were Amfleet; I haven't tried any of the newer models, even the "old" Acelas!

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hhf Mar 22

@grvsmth nice write-up! Fits my observations. I measure CO2 since before Covid as studies show that decision making gets worse with CO2 levels and this is important for workshops and crisis-rooms.

As for your primary health provider / mothers doctor: if they can not get fresh air in, they should get an air purifier. As you wrote in your other post, that will not affect CO2, but it will affect all airborne pathogens.

Their judgment may impaired, though…

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Angus Andrea Grieve-Smith Mar 22

@hhf Thanks! I'm not a ventilation specialist, so I recommended to my doctor that she bring one in.

Unfortunately, my mother died last year, probably due to complications from RSV and pneumonia. She had gotten vaccinated against COVID, but refused vaccination against the flu, RSV or pneumonia, and resisted wearing masks and eating outdoors.

But she was 86, had a good life, she was suffering from Parkinson's, and told me several times she was ready to go, so I feel like I did what I could.

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hhf Mar 22

@grvsmth sorry for your loss!

You don’t have to be much of a ventilation specialist to understand that any air filter in a room will improve the situation.

Long term it will be updates to building standards etc. which will hopefully improve the status everywhere.

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Angus Andrea Grieve-Smith Mar 22

@hhf Of course you don't have to be a ventilation specialist, but as you pointed out, it's generally bad to have high carbon dioxide in a medical office. The doctor really needs to get the airflow in her office fixed.

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Tim Bray Mar 22

@grvsmth Had a medical appointment recently on the 14th floor of one of the General Hospital’s towers. The elevator was slow, stopped at nearly every floor and people shuffled out and squeezed in. Jam-packed, at least 15 people. Two of us had masks. *shudder*

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Flaming Cheeto Mar 22

@grvsmth in my much smaller period of sampling I'd just like to add that restaurant and bar patios that are wrapped on 3½ sides with transparent plastic are pretty bad. There's no air movement. Better to be indoors next to an open window.