I finally got this sensor to work but instead I use this lib: https://github.com/nara256/mhz19_uart
Another very useful source of information is this: https://revspace.nl/MHZ19#command_0x62_.28device_name_.2F_id.29
Take note that is the MH-Z19B the methods isWarming() and getStatus() do not work.
Can you please share the values that you are getting? I'm getting around 1500ppm and it is alarming by these website standards:
I didn't have the opportunity yet to get the sensor outdoors.
Thank you in advance