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Comment by OutOfHere | Hacker News Reader

I use air purifiers mounted on my windows, running continuously except in the deep summer and deep winter. This makes my air contain 50-100x fewer particulates than the outdoor air. In contrast, the best I can achieve with floor air purifiers as people have them is a 5-10x reduction. The window purifiers also keep excess CO2 and VOCs out.

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> The window purifiers also keep excess CO2 and VOCs out.

I assume you mean that the increased air-exchange (purified or not) helps CO2 that originates inside the house to leave promptly? (Equalizing it with the outdoors.)

Literally "keeping CO2 out" is a much trickier and more-expensive proposition.

You are quite correct on both counts.

Health improvements are not measurable any more if you go below 5 mcg/m2 average level of PM2.5 particulates. For 50x reduction to be beneficial, you need to live in an area where the pollution is 250 mcg/m2, which is an extreme level found only in a few unfortunate places on Earth. 5-10x reduction is reasonable almost everywhere.

I know precisely the subjective difference between a 5x reduction and a 50x reduction. Only the latter feels sufficiently good to me, and my brain operates better with it. You will know it when you experience it. Maybe it's my middle-aged brain that needs the extra support. I live in an urban area near traffic. Lately there intermittently also has been wildfire smoke coming down from Canada.

You have activated carbon to filter out the VOCs?

Yes, the filter absolutely has an activated carbon layer in it in addition to a HEPA layer. I understand that activated carbon doesn't last long. I have been changing the filter every two months.

Note that because this purifier is mounted at the window, it filters incoming air from outside, not the indoor VOCs that are already in the residence. The indoor VOCs will simply have to get exhausted from elsewhere due to the air pressure.

What I am suggesting is that my need for activated carbon is slightly less because I am rapidly pushing the VOCs out in the resulting exhaust.

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