My DIY sensors[1] (temp/humidity) are running on attiny84 and 3xAAA batteries, which I really like as they last for about a year (sending updates every ~1 minute and then sleeping).
But because I'm not using a voltage regulator, since that would mean losing the very nice onboard voltage monitor, it's been really hard to find some CO2/PM2.5 sensors that can work from ~5V to ~3.4V.
> Working voltage 4.5 V ~ 5.5V DC
> Operating Voltage 3.3V / 5V
Guess I need to keep looking, but thanks for linking the specific models!