The Effects of Temp & Barometric Pressure on CO2 Sensors

From BAPI, Inc.

co2_btns_021 This 2 page, FREE and downloadable App note begins:

Carbon Dioxide (CO2) in air is normally measured in Parts Per Million (ppm). At 1,000 ppm CO2, a volume or air containing one million air molecules would contain a mixture of 999,000 air molecules and 1,000 CO2 molecules.

“The volume of air necessary to contain one million air molecules is affected by air temperature and air pressure, also called Barometric Pressure. As the pressure decreases, the volume needed to contain one million air molecules increases. The opposite is true of temperature. As the temperature decreases, the volume of air needed to contain one million molecules decreases.

“Although the volume of air is affected by temperature and pressure, the concentration of CO2 is not affected. If you started with 1,000 ppm of CO2, then you finish with 1,000 ppm of CO2 despite the changes in the air volume.”

The rest of the story is online on the BAPI website

Building Automation Products, Inc.
750 North Royal Avenue
Gays Mills, WI 54631

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