[dws]

Interesting that they don't recommend TVOC sensors. I spent a few months trying to get a set of CSS811 sensors to behave. They'd consistently, but erratically, drift upwards into "you should be dead now" territory, returning to believable levels only when fully reset.

[ahaucnx]

Author here.

We do only recommend TVOC sensors to detect spikes but not for any specific concentration measurements. For spikes, TVOC has some use cases, e.g. detecting aggressive cleaning chemicals or leaking chemicals, e.g. in an art classroom if somebody forgot to close the pot with color.

[dws]

Agreed, thought it seems unlikely to me that the sensors I was testing were reacting to any sort of leak or out-gassing. They consistently showing a steady increase in TVOCs over 12 hours in an empty room with a window cracked.

[numpad0]

Was it the Sparkfun BME280/CCS811 combo by chance? It seemed to drift up when temperature has positive errors and downward if negative, and the heater in CCS811 was affecting temperature reading on BME280. Adding a second temperature sensor delayed drift somewhat in my case, though the effect was marginal.