My old Awair has a Telaire T6703 CO2 sensor; the newer ones probably have something similar. I also had a standalone sensor at one point, they're a thing too.
And Tindie has a slew of ready-to-order air quality stations too.
Have you had a good experience with Awair? The last time I looked it seemed like they had no recommended way to clean the sensors. And in my limited experience PM2.5 sensors do need periodic cleaning to remain accurate. My air filter has one and the manufacturer recommends a bit of alcohol and a puff of air.
Their old one had an issue with the dust sensor clogging.
The new ones use the Honeywell sensor. It has a tiny fan on it (inaudible in a quiet room from 5 inches away); mine ran well for a couple of years until I knocked it off my desk. After that, the fan started rattling, so I ordered another Honeywell sensor ($40) and replaced it (no soldering required, just a screwdriver). That sensor's datasheet doesn't have any cleaning instructions, so I don't think it's a big issue.
