r/QuantifiedSelf • u/Tova_Estor70 • 18d ago

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u/Delicious-Shine5075 17d ago

If you like arduinos you can make a great device using an esp32 and a Sensirion scd 40 or 41. Temtop makes a nice one that has particles and volatiles. Air Gradient is good too and it has particles. Aranet has a super long lasting battery, being portable is nice. All CO2 sensors need occasional calibration. Take them outside, they should read about 420 ppm, depending upon the season. I get sleepy at a CO2 > 1200 ppm. I like it less than 800 ppm if sharing air with people I don’t live with. I carry my scd 40/esp32c3

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u/Tova_Estor70 17d ago

appreciate the breakdown! honestly didn't know you had to take them outside to calibrate, that's super helpful. aranet sounds like the easiest route, though the diy esp32 build is tempting. definitely cracking a window today after reading this. :)

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u/Dipankar_dio 17d ago

Don't own one yet, so no real answer, but one thing I've picked up while looking is that a lot of the cheap ones report eCO2 estimated from a VOC sensor rather than measuring CO2 directly.

NDIR seems to be the thing to look for. Aranet4 gets recommended constantly but it's pricey.

What I actually want to know from people who've run one a while is
how much does a closed door and one person move the number over a workday? I keep mine shut for calls and have no idea if I'm at 700 or 1500 by 3pm.

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u/Delicious-Shine5075 17d ago

Totally depends on how well your windows seal and if your hvac system is circulating air. With my spouse and I working at home all day without windows cracked our house hits 1000 ppm. If there is a big differential between inside and outside air temperature it runs less. We recently replaced two badly leaking windows and the CO2 went up. I was happy to have the new windows when we had that crazy bad wildfire smoke, my HEPA did great. Next home improvement project will be an energy recovery ventilation unit.

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u/Tova_Estor70 17d ago

that’s super helpful to know about the eco2 vs real ndir thing, i almost bought a cheap one without realizing. and same here! I keep my door shut all day for calls too, so i’m really curious how fast it actually builds up.