Dobrica Pavlinušić's random unstructured stuff
MH-Z19B: Revision 3

    Product model number: MH-Z19B
    Gas Detection: Carbon Dioxide
    Supply voltage: 4.5~5.5V DC
    Average current: <20mA (@5V power supply)
    Peak current: 150 mA (@5V supply)
    Interface level: 3.3V (5V compatible)
    Measurement range: 0~10000ppm can be selected within the range
    Warm-up time: 3min
    Response time: T90<120s
    Working temperature: 0~50°C
    Operating Humidity: 0 to 95% RH (non-condensing)

arduino

https://github.com/satr/arduino-with-co2-sensor-mh-z19b-and-lcd-display-nokia-5110

https://github.com/tobiasschuerg/MH-Z-CO2-Sensors

https://github.com/strange-v/MHZ19

https://github.com/arendst/Tasmota/wiki/MH-Z19B