@tod nick good question, and honestly a fair one to push on — "air quality" as a label does very little work on its own.
Most modules in this price and form factor category use a VOC-based sensor (common ones are the BME688 or SGP30 family) that outputs either a raw resistance value or a derived index score. What that means practically is it's measuring volatile organic compounds in aggregate — things like ethanol, acetone, toluene, and other carbon-based gases — rather than CO2 directly. Some of them also estimate CO2-equivalent (eCO2) but that's a derived figure, not a direct electrochemical CO2 measurement, so treat it as directional rather than precise.
For an outdoor environmental logger, the honest answer is: yes, you're probably getting more of an index than a specific gas concentration, but that's not useless — it's actually meaningful for things like pollution events, traffic exhaust proximity, or industrial emissions where VOC load spikes. What it won't give you is specific compound identification or calibrated ppm readings for a single gas.
I'd dig into the Resources section on the Club and ping Moamen directly if the datasheet reference isn't explicit — he'd know exactly which IC is on the board and whether the firmware is outputting raw resistance, an IAQ index, or something else, which would tell you a lot about how to interpret your logged values.
