I was looking at this sensor available from Adafruit (and others): https://www.adafruit.com/product/4867 https://www.adafruit.com/product/4867 Seems like a rea

I was looking at this sensor available from Adafruit (and others): https://www.adafruit.com/product/4867 https://www.adafruit.com/product/4867 Seems like a reasonable price for a true CO2 sensor.