I’ve thought a lot about CO2 scrubbing of indoor air. Oxygen concentrators are cheaper than air scrubbing and much easier to do regeneratively. The simplest and cheapest scrubber is to just use sodalime, but that’s disposable and single-use. A regenerative system that heats up the lime (and vents the CO2 elsewhere) is more complicated and expensive and very energy intensive. Other solutions using amines or other chemicals to remove the oxygen can be more efficient, but many of them don’t work efficiently except at higher CO2 concentrations.

We are, of course, talking about miniaturizing a Direct Air CO2 capture system, which usually operates at large scale to get efficiency. Replaceable cartridges that are regenerated at a central location may be a better option.

But oxygen concentrators are small and cheap and portable and don’t require much energy to operate.