Hi, Co2 levels like that are severely high and will cause you to have a lot of issues. I had some issues with poor ventilation and headaches in my apartment, and my solution was to run the bathroom fan all the time - this gave me enough ventilation to feel much better. You're basically suffocating at 3000 ppm.

It's important to measure this somehow - I do this with a $100 Co2 sensor and display I got off amazon, but you seem to already have these sensors available.