I've wondered about this. If I install an air monitor in my room, what do I do if it shows low quality? Open my window in below-freezing winter temps? Hire someone to overhaul my furnace and vents?

If you aren't willing to do anything about it then why bother with the air monitor?

If you only have a single room then your options are limited, however moving rooms or opening a door to a different room and turning on a fan to increase circulation?

If it is CO2 then you could invest in a houseplant or two.

Houseplants do not exchange anything near significant amounts of CO2 for this purpose.

The long term answer is to improve the HVAC: reconfigure for more external air mixing (commercial), or find a way to install an HRV or ERV, or open a window, but that can be expensive or impossible depending on the situation.

The houseplant was just the cheer them up while they slowly suffocate since they weren't going to do anything about it.

Like a button that does nothing.

I'm currently renovating a house in The Netherlands, we're installing a heat pump and to make the place more efficient we also replaced the glass with triple glazed (but without vents in the frames as they let heat escape). Given that we were effectively making our house a "sealed envelope" we had to add mechanical ventilation (ERV) to ensure proper airflow around the property. As you can imagine, retrofitting ducting around an old house required a LOT of creative work!

> If it is CO2 then you could invest in a houseplant or two.

This seemed wrong to me, so I checked and it seems like you'd need hundreds of houseplants to make any significant difference: https://www.realhomes.com/news/do-house-plants-remove-carbon...

Seems like there'd be a market for a CO2 > O2 exchanger of some sort. I don't know enough chemistry to recognize why this is probably too difficult for commercial viability.

if you keep the window open all year, dress appropriately and avoid heated buildings you don't notice how cold it is. I switch it on a few years ago because my cat is getting really old. I now feel cold if its 17 C or below.

That is an extraordinarily climate-specific recommendation. It’s currently a fairly mild 30F/-1 C outside my house and even that is obviously way too cold to go without heat completely.

You are conditioned to think you are and feel cold. Look how cold some countries and regions get? The people working outside there are not a different species. The trick is to get used to it gradually. I didn't say it was fun or easy.

I spend a good bit of winter working outside but with physical activity it is much easier.

Do you have other ideas? I mean, it would be nice? I cant think of anything else besides migration.

>Look how cold some countries and regions get?

As someone from said countries and regions, people living outside freeze to death here. Long before you get to that point your water pipes will freeze, leaving you without running water. The pipes will then burst and flood your house if you don't address it quickly enough. You can certainly heat it to a lower temperature and occasionally crack open a window for some fresh air, but there's a difference between conditioning yourself to be comfortable at 17C and -30C.

Open the window. In my apartment I keep a single open somewhere between a millimeter and a centimeter when it's below freezing, depending on the temperature and wind. That's enough to keep my CO2 sensor happy (try to keep it around 550), and it (shockingly) doesn't seem to affect my heating bill all that much. There's a cold corner of the room next to that window, but the rest of the apartment stays just as warm. (I have a thermostat that controls heating.)

I also keep a humidifier running full blast (silently) because otherwise it will get crazy dry on some days.

> I also keep a humidifier running full blast (silently) because otherwise it will get crazy dry on some days.

Heh, I usually keep the dehumidifier running, I don’t think I’ll ever need a humidifier. Currently, 80% RH (7g/m³) outside, with indoor levels all slightly above 60%.

That cold corner risks becoming a condensation point and so developing mold.

It doesn't though. The relative humidity at 70°F is only 30-35% with the humidifier running full blast. Because it's often 7-15% without the humidifier. Because the air coming through the window is bone dry.

The problem in the winter here is keeping enough humidity in the air. It would be nice if I ever had to worry about condensation. ;)

So, this works with temperatures down to freezing and below (don’t know what the cut off is, maybe there is none given this planet’s temperature range) and if you heat and dress appropriately (i.e. not up to super high temperatures – around 20°C or so – and if you have a sweater or jacket on or can put one on).

Obviously you also need the appropriate building for it. (So no fancy passive house. No fancy air conditioning – which is quite uncommon where I’m from anyway.)

Generally, if you only open the windows for five minutes or so the air will cool down substantially (the right moment to pull on that sweater) but everything else (walls, furniture) will not really cool down that much, meaning the room will be quick to be back at an appropriate temperature.

We learned and did this in school, often do it in offices and meeting rooms and also at home. Though, admittedly the temporary unpleasantness does frequently lead to people postponing opening the windows forever and ever. (Once every 90 minutes in a classroom setting might not be enough.)

In those settings a CO2 traffic light as an obvious visual indicator would be super helpful.

I imagine people are mostly perceiving humidity and heat when they notice a room getting stuffy.

FWIW, the frustrations of not being able to change high CO2 levels was just a topic of discussion over on https://news.ycombinator.com/item?id=34648021