We picked up the Aranet 4. Things were fine until we replaced our windows with fancy new ones. Our air quality plummeted, CO2 > 2200.

We got a new air exchanger installed, connected to our existing forced air hvac system. It runs at a low speed 24x7, which keeps things at a reasonable level.

It has a few settings like: continuous, 20 minutes/hour, 40 minutes/hour, and "humidity control". Nothing for CO2 control though. I have aspirations to hack the control module and make it care about CO2, but I've also got two kids and a startup so who knows how long that will spend in the backlog.