Smoke has enveloped the outdoors in my area, the pm2.5 in the area is high, currently at levels categorized as very unhealthy AQI 201-300.

I don't have many indoor plants so the CO2 level inside is real high, our CO2 meter (Netatmo) device is currently reading 3596ppm.

Netatmo details anything over 2000 as dangerous

What is a good framework for determining risks? Would going outside with a air filtration mask make most sense in the immediate term?

  • 1
    I'm sorry to hear about the situation there! I can't offer expert advice but CO2 (carbon dioxide) is certainly dangerous, and elevated levels will cause noticeable effects. However CO (carbon monoxide) is extremely dangerous and its effects are difficult to notice until one is at serious risk of losing consciousness. The reason that phones have CO2 sensors is that they are relatively easy to make specific to CO2, whereas most sensors for CO are also affected by other gases. One would really like a CO sensor, but CO2 sensors are easier to market/sell.
    – user16606
    Commented Sep 13, 2020 at 4:20
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    For more on CO sensors see chemistry.stackexchange.com/a/118050/16035 and for CO2 sensors see chemistry.stackexchange.com/q/89726/16035 and also earthscience.stackexchange.com/a/18641/6031 CO2 was chosen in the filming of Andromeda Strain specifically for its obvious symptoms, had they used CO the effects would be just as deadly if not more, but unnoticeable at first movies.stackexchange.com/q/110281/45856 and the monkey could not have been so easily revived.
    – user16606
    Commented Sep 13, 2020 at 4:23
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    @uhoh Interesting answer and comments about Andromeda Strain over on Movies.
    – Carey Gregory
    Commented Sep 13, 2020 at 5:38

1 Answer 1


Given the levels you're describing, I'd stay inside, but it's a close call.

Pulling up a random Carbon Dioxide Safety Data Sheet, the long-term exposure limit for carbon dioxide is 5000 parts per million according to NIOSH, ACGIA, and the latest OSHA standards (OSHA 1989 permitted 10,000 ppm). The 3600 ppm your meter is reporting is below that, while the PM2.5 level outside is solidly into the "unsafe" range.

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