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And this is why I never bought one, even though I want one.

I can't seem to find a reasonably priced one that is actually accurate.

PM2.5 have decent accuracy and are certainly useful at low price points, RH/temp work fine, particularly with separate sensors. Pressure works fine but is pretty useless. NDIR based CO2 (ex. Sensirion SCD31 or 41) also work fine.

TOC is a bit of a mystery, it can probably detect relative change. I've used them in a lab to monitor solvent vapor and you can detect changes, hard to quantify but don't need to most of the time.

> NDIR based CO2 (ex. Sensirion SCD31 or 41) also work fine.

SCD4x series are photoacoustic rather than NDIR, but they are true CO2 sensors and seem to work rather well given the size.

I guess, yes and no. Technically the scd41 emits IR, it just doesn't detect transmitted light, instead sound produced by the CO2 that absorbed the light.

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