Remember how there used to be activated charcoal insoles, to get rid of stinky foot odors?
You can now get charcoal in bags that let UV rays in. The idea is that every month, you put the bags out into the sunlight for an hour or two, and activate the charcoal again. And then you bring the bags into your house, and the charcoal gets rid of any impurities in the air (including odors), as well as absorbing moisture if you put them in a damp area. You can also use them in fridges (or shoes).
The bags only last for about two years, at which time you open the bags and put the charcoal in your garden as fertilizer.
They’re not too expensive, so I bought some bags and I’m trying them out.
Sure enough, they really started working very quickly, and the air does seem cleaner. I did smell a little whiff of charcoal at first, with one bag, but that was gone within about an hour.
I don’t know about the dampness, because I don’t really have any damp areas. (Obviously, you wouldn’t want it fighting any humidifier in a non-damp area, either.)
Apparently it started as a US company product, but now there are tons of Chinese copies. (Other than that, I don’t think brand matters.) So pick carefully. Your local garden center or hardware store might carry them.
Aliens in This World 
A much better use for activated charcoal than the cigarette filters we saw advertised frequently back in the pre-ban days. Buy American. š