For at analysere kuldioxiden i udåndingsluften udsendes infrarøde bredbåndsstråler fra en infrarød strålingskilde skiftevis gennem målekammeret og et referencekammer vha. en stråle- chopper.
To analyse the carbon dioxide in breath a broad band infrared radiation bunch emitted by an infrared radiation source is alternately sent through the measuring chamber and a reference chamber by means of a beam chopper.