CO2 CO2


Principles Carbon dioxide (CO2) is a colorless and odorless gas that exists in the earth's atmosphere and which is dangerous in high concentrations. The proportion of CO2 in natural ambient air is about 0.04 % or 400 ppm. When humans and animals ex- hale this gas, it is quickly mixed with the ambient air, including in rooms that are well ventilated.


A high CO2 content becomes apparent in humans through rapid fatigue and loss of concentration. The negative effects become noticeable more quickly in small rooms in which there are many people (e.g. conference rooms).


In order to initiate suitable countermeasures such as an increase in the supply of fresh air, it is important in modern climate control systems to measure not only pa- rameters such as relative humidity and temperature, but also the CO2 content. The concentration of CO2 is regarded as an important indicator for the indoor air quality.


Guidelines 350 - 450 ppm 400 - 1,200 ppm > 1,000 ppm Fresh air outdoors Room air


Fatigue and loss of concentration become apparent


5,000 ppm (0.5 %) 38,000 ppm (3.8 %) > 100,000 ppm (10 %)


Maximum permis- sible value at the workplace during an 8-hour workday


Breathing air (direct exhalation)


Nausea, vomiting, loss of conscious- ness and death


Measurement technique


The measurement technique is based on the principle of NDIR (non-dispersive infrared) sensors. This gas sensor works as a spectroscope and analyzes which wavelengths emitted by a light transmitter reach a receiver.


Calibration


All probes are pre-calibrated and have a lifetime of more than 15 years in normal applications.


The automatic baseline correction means the sensors require no further calibra- tion if they are used in indoor air applications.


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