We use these at office in conference rooms or 1:1 rooms, and encourage people to keep CO2 levels below 700-800 (an empty room 450-550). Very high quality, a half dozen all agree perfectly on all sensors. They support API.
# SAF Aranet4 Home
Wireless Indoor Air Quality Monitor for Home, Office or School (CO2, Temperature, Humidity and More) Portable, Battery Powered, E-Ink Screen, App for Configuration & Data History
- The perfect companion for indoor environments, allowing you to monitor CO2 levels, temperature, relative humidity, and atmospheric pressure in real-time
- Easy for anyone to use – the color coding and the optional buzzer warns you when the CO2 concentration gets too high
- Power-efficient e-ink display ensures super long battery life for this wireless device (up to 4 years)
- Smartphone app for viewing and analyzing historical data up to 14 days history (supports iPhone and iPad with iOS 12 or later, Android devices with Oreo 8.0 or later, compatible with Bluetooth 4.1 or later)
- Uses nondispersive infrared sensor (NDIR) technology for most precise and reliable CO2 measurements
I love mine too. Been meaning to set up some longer term logging since the app only holds two weeks (and I've noticed it often wipes out data faster than that).
Here's another upvote for the Aranet4 device, I first found it recommended on HN and have been happy with it ever since purchasing it a couple of months ago. Integrated into Home Assistant using a couple of lines of Python code scheduled by AppDaemon.
# SAF Aranet4 Home
Wireless Indoor Air Quality Monitor for Home, Office or School (CO2, Temperature, Humidity and More) Portable, Battery Powered, E-Ink Screen, App for Configuration & Data History
- The perfect companion for indoor environments, allowing you to monitor CO2 levels, temperature, relative humidity, and atmospheric pressure in real-time
- Easy for anyone to use – the color coding and the optional buzzer warns you when the CO2 concentration gets too high
- Power-efficient e-ink display ensures super long battery life for this wireless device (up to 4 years)
- Smartphone app for viewing and analyzing historical data up to 14 days history (supports iPhone and iPad with iOS 12 or later, Android devices with Oreo 8.0 or later, compatible with Bluetooth 4.1 or later)
- Uses nondispersive infrared sensor (NDIR) technology for most precise and reliable CO2 measurements
https://smile.amazon.com/gp/product/B07YY7BH2W/
https://github.com/Anrijs/Aranet4-Python *
* Note: Smart Home Integrations must be enabled in Aranet4 mobile app for full support