I've got an Aranet4 and started tracking CO2 and submitting it to IndoorCO2Map (via https://whn.global/indoor-co2-map-co2-monitoring-and-data-co...), but after a short period of time, there aren't really any surprises. Carrying a CO2 detector everywhere seems like mostly a way to give yourself anxiety.

If it's crowded now, or was recently, the CO2 is going to be high. If the building is old, or low volume, the effect will be worse.

Nightingal, and Robertson before her, argued for better designs in hospitals to overcome these issues. We are over 150 years on from this arguement which has already been proven.

Using a digital sensor isn't required. The spread of various Corona viruses and others increase during colder weather and are more likely to spread in enclosed environments with limited air flow.

Cafe door shut, no air exchange in place, it's winter and half the clientele are reaching for hankies. Your probably catching a cold.

I have a CO2 detector at home and bought some for family members, but I have never had a portable one so they stay at home. Some of the high CO2 ppm numbers in the article make me want to double check them. My vague understanding form reading the manual of the one I bought and watching how the numbers can be thrown off by cleaning products used near them make me wonder how much these high numbers are from sources other than CO2. That said I would still suspect that the a good chunk of the relative differences would be from CO2 changes.

The article linked in the first paragraph is almost more interesting to me[1]. Some of these places, like the subway, have air frequently circulated that can filter aerosols but leave CO2; this limitation makes me somewhat doubt its usefulness as a proxy for disease transmission risk.

Apart from disease transmission, since I've gotten a CO2 monitor in my apartment I've noticed that running the gas stove or oven for even a little while will make a huge spike in CO2.

[1] https://grieve-smith.com/ftn/2026/02/so-you-want-to-monitor-...

Buying a (relatively expensive) CO2 monitor is one of those purchases that I was pensive about at first, but have zero regrets about a few years later. I was ignorant of a lot of things related to air quality, CO2 in particular. We were foolishly running a gas stove in a house with no ventilation, which probably had us up in the 1500+ range every time. This may seem like an obvious no-no to most of you but it was not a lesson we had ever learned.

You also get to see some other interesting observations, like how local construction digging up dirt on your street can cause elevated radon levels for months on end.

Am I the only person here confused by the line the author draws between high CO2 levels and high transmissibility of viruses. I think they’re confusing correlation for causation here.

Very interesting article, but remember, making a room more airy will not mitigate the long term effects of CO2 on the Earth.

Older people may remember the push to make your house more energy efficient. So, seems you have a choice, higher energy bills or higher indoors C02.

So what is needed, move off fossil fuels. I remember seeing during the covid lockdown, C02 Levels did not raise for the first time in decades and I think they may have fell a little. That is because auto traffic decreased a lot. Right now I believe we are on our way to +2.5C :(

The problem isn't to breathe CO2, it's pumping it in the atmosphere... This article really misses the point.