What about HCHO, did you research this sensor as well? I see a calibrated / compensated HCHO measure on one of your graph, and I’d be very interested in your maths behind it. I have just noticed that it definitely has a strong cross-sensitivity to h2s and would love to know how can i minimize it.
cannot tell you too much about formaldehyde, but it’s in line (ish) with my dyson sensor
also be aware that almost all my previous formulas are messed up since new firmware came out, they probably fixed some stuff and no more aggressive adjusting needed, I should dedicate more time