The most recent discussions of different CO2 monitors on the market I could find on LessWrong[1] were a few years old, and it seems that prices have come down somewhat since then. I found this positive review of a CO2 monitor manufactured by Qingping,[2] and then found it on AliExpress for about $40 (though it seems to have gone up by about $5 since I ordered it). The review found that its measurements agreed quite well with the more expensive Aranet4, and it uses a Sensirion SCD40 CO2 detector, which is apparently well-respected.
The review refers to it as the SmartAir, but the versions currently being sold on both Amazon and AliExpress have "qingping" in the location where the "SmartAir" branding would otherwise go. I assume it's the exact same product seeing as the product listings appear otherwise identical. ↩︎
You can buy a even cheaper one from taobao, this one is $20 before shipping (but I expect the buying experience to be quite complex if you're outside china)
I found a seemingly-high-quality CO2 monitor here for less than $50, or on Amazon or from the manufacturer's website for $70.
The most recent discussions of different CO2 monitors on the market I could find on LessWrong[1] were a few years old, and it seems that prices have come down somewhat since then. I found this positive review of a CO2 monitor manufactured by Qingping,[2] and then found it on AliExpress for about $40 (though it seems to have gone up by about $5 since I ordered it). The review found that its measurements agreed quite well with the more expensive Aranet4, and it uses a Sensirion SCD40 CO2 detector, which is apparently well-respected.
I'm not entirely sure what the think of the evidence around CO2 negatively impacting cognition, but it seems plausible enough to be worth spending <$50 on a monitor.
In the comments of this post and this post. ↩︎
The review refers to it as the SmartAir, but the versions currently being sold on both Amazon and AliExpress have "qingping" in the location where the "SmartAir" branding would otherwise go. I assume it's the exact same product seeing as the product listings appear otherwise identical. ↩︎