I live in Canada, where radon is an issue. The item I got from Airwave gave me a half year of data that was close enough to the safety limit that I decided to add radon mitigation to my home. I then lent it to a friend who decided to do the same.

I have multiple CO2 meters in the house that helped me determine that there were no major issues with airflow, and led me to consider other ways to improve our sleep quality. This was also kinda helpful for me during parties; I'm usually not thinking about opening the window during winter, but when the CO2 level passes 1200 or so, I'll usually open it a crack.