We borrowed a sensor for a few weeks and measured different rooms. The readings are especially high when we invite people. (We cook electric , and I think the stove has little to do with high CO2 in a living space.)
The conclusion is that we need to ventilate more. Especially in the bedroom. Sometimes it’s hard to find a good balance between ventilation and heating.
I should add: it was rather fancy as it could display graphs and such. But in the end that not very useful, after a few days of watching the readings you start to understand when CO2 increases (people) and decreases (ventilation). It never reached unhealthy levels of CO2 in our home.
The conclusion is that we need to ventilate more. Especially in the bedroom. Sometimes it’s hard to find a good balance between ventilation and heating.