Calibration to measure CO2 by sensor mq 135

Does anyone know how to properly calibrate this sensor?
I need to apply for an academic project on air pollution.
I bought the sensor but I do not know how to calibrate it and in its datasheet it does not teach much, it is able to measure several gases, but I specifically want CO2 to check the emission levels at a thermoelectric plant near my city.
I could only connect the sensor to the serial port and I can see from the monitor that it measures gases, but which one exactly .... does not know, besides having to calibrate for an accurate measurement using a reference environment.

I hope someone can help me as soon as possible, thanks to everyone who can see and spread this topic to find someone who can give me an answer.

Thank you guys,

João Paulo Alves Sartorello
Graduating in sanitary and environmental engineering by UFMT

Unless you are using magic, the only way to calibrate anything, including a co2 sensor is to compare it to a sensor that has been calibrated by a certified person and it is still within the valid time period. As you yourself wrote "besides having to calibrate for an accurate measurement using a reference environment.".


I’m not sure if this is the same thing, but, I work in the Kinesiology department at a university and we do alot of VO2 measurements which involve measuring O2 and CO2 gases being exhaled by the test subject.

In order to get accurate results, we calibrate it each time we run the test.

To calibrate, we measure two known gases with the device… usually 20% O2, 0% CO2 for the first gas, and 16%O2 and 5% CO2 for the second. This gives us two points on a curve for each sensor. Then it’s just a matter of applying the offset, assuming the sensor response is linear…

Hope that helps a bit…


MQ135 is not a realiable sensor, it is used on alarms.
You should use an NDIR CO2 sensor. Good sensor are expensive.