Anyone else ever think of somehow building an at-home carbon-removal system, for lower carbon content in the air of your living spaces? I know it's a silly idea, but one that has occurred to me from time to time.

Depends on the approach you want to take. It's possible but IDK if you'd see any sort of health benefits from simply lowering the CO2, you'd probably also want to increase the O2 content.

This is actually a crazy thing that some of the very wealthy are doing in mountain homes. They have O2 tanks setup with their homes so that when they arrive they don't experience altitude sickness.

https://www.outsideonline.com/outdoor-adventure/snow-sports/...

Makes one wonder about the absurdly large number of physiological and psychological changes we've seen in people since the 70s-80s when AC started becoming completely ubiquitous. Before that time, at least in warmer climates, you'd pretty much always have a window open. In some ways we've already been running a decades long high CO2 exposure experiment.

The most practical way to do this is to ensure that your indoor air CO2 levels aren't significantly elevated over outdoor levels. One common way to do that (apart from opening windows) is to use a balanced ventilation system like an ERV or HRV. Those constantly exchange indoor air for outdoor air, and exchange a lot of the heat in the process to reduce energy losses.

Doesn't help if atmospheric CO2 levels increase to unsafe levels, though.

Yeah, too many homes were built without fresh air intakes into the HVAC systems. There are definitely reasons you don't want it always pulling in outside air (temp and humidity differences, for example), but it would be nice to have the option to do it once a day just to freshen things up.

Uh, do you mean house plants?

There is also a Ted talk about taking this to an extreme, which does seem to anecdotally work: https://www.youtube.com/watch?v=gmn7tjSNyAA&pp=ygURdGVkIGthb...