How can measurement errors be avoided?

Principles for CO2 measurement

Measurement of the CO2 value of indoor air is dependent on the needs of the person taking the measurement.

Basically, a distinction is made between two different measurement requirements.

  • Stationary, in other words constant, and if applicable with regulation of an HVAC (heating, ventilation and air conditioning) system. 
  • Portable, in other words with a handheld instrument for sporadic measurement at any chosen point, e.g. for workplace assessment.
Universal IAQ instrument testo 400

The following points must be taken into account to get a reliable result when taking a measurement:

  • Both fine dust and condensation influence the optical path and therefore the measurement.
  • After the instrument is switched on, there is a sensor warm-up phase of approx. 30 s.
  • If the ambient temperature changes (change of measuring location, e.g. indoors to outdoors or vice-versa), the probe needs a few minutes to adjust.
  • The CO2 concentration in the sensor requires approx. 60 s to adjust to the environment.
  • As a rule, normal air movement is all that is needed for sufficient mixing of the CO2 gas with the other components of the air.
  • The content of the air we have breathed is approx. 40,000 ppm CO2. Therefore, you should not breathe directly on the probe or in its direction.