Thank you for your responses.
I'll try to turn on auto-calibration and move the sensor out of the window for a couple of days.
I'll see what changes. Then I will unsubscribe

I put the sensor out the window, after 20 minutes it showed 400 PPM. Autocalibration did not include. When I breathe on it for a long time, it shows 5000 PPM. How do I know which readings are normal in this range and which are critical? The instructions say that: 400-600 PPM - Clean Air 600-800 PPM ...

I installed a sensor in the bedroom. I have a reading of 1700-2500 PPM. Is this the norm for the range 400-5000 ?? I read that the readings should be 600-1000, but this is probably for the range of 400-2000 PPM

Where did you install your sensors and what are their readings?

My native language is Ukrainian. Your measurement range 0-2000 was set by default? How do you connect your sensor? PWM or Serial Port?

TD-er, what is the measuring range of your MH-Z19 ?? (sorry for my english using google translator)

Hello. I am using the MH-Z19B sensor with ESPeasy. I have a measuring range of 400-5000 PPM. Can I change the range to 400-2000 PPM in the ESPeasy interface? I connect via HW Serial0 GPIO-3 (D9) TX / GPIO-1 (D10) RX. Thanks