From Wikipedia - Reading time: 3 min
A carbon dioxide recorder (or CO2 recorder) is a machine that can record the level of carbon dioxide at different times. It is more sophisticated than a carbon dioxide detector which only has to indicate the presence of carbon dioxide. There are three main types of carbon dioxide recorder: chemical, physical, and electrical.
The chemical carbon dioxide recorder, sucks the gas through a chemical that absorbs carbon dioxide. They include the Simmance combustion recorder;[1] Hays automatic CO2 recorder, and electroflo CO2 recorder.
The Arndt carbon dioxide recorder used a potassium hydroxide solution to absorb carbon dioxide.[2]
The Uehling recorder uses the chemical, sodium hydroxide to absorb the carbon dioxide, and measures the change in volume of the gas.[3]
The physical carbon dioxide recorder, includes Webster CO2 recorder. The Remarex carbon dioxide recorder uses vanes spinning in the gas under test and the air.[4]
Electrical recorders use a thermal conductivity method, where the resistance of a heated wire is measured.[5][6]
Carbon dioxide recorders can be handheld, or wall mount. They can have an audible or light indicator alarm if level is too high. Units can also measure humidity and temperature.[citation needed]
Carbon dioxide recorders have been used in schools and hospitals to determine whether enough fresh air is being circulated. A carbon dioxide recorder can be used to measure the composition of flue gas to check if combustion is at its most efficient.[3] In agriculture, they can be used to measure levels of carbon dioxide in greenhouses, where the levels are deliberately elevated.[6]