Aranet4 Home
The CO2 monitor made famous by @levelsio on X. I use it to check the air quality of my home and office.
About
The Aranet4 Home measures CO2, temperature, humidity, and atmospheric pressure with a crisp e-ink display and 2-year battery life from two AA batteries. Uses an NDIR sensor (the accurate kind) with color-coded alerts when air quality drops. Bluetooth syncs to your phone for historical data, and the whole thing fits in your pocket for checking air quality wherever you go.
Turns out most indoor spaces have terrible ventilation, and you don't notice until you see the CO2 readings climb. Schools, offices, gyms, planes - all worse than you'd think. Having actual data instead of guessing makes it easier to know when to crack a window or take a break outside. The e-ink screen means it's always visible without being annoying, and the battery lasts long enough that you forget it needs them.
