This International Standard specifies a non-dispersive infrared spectrometry method for the continuous analysis and recording of the carbon monoxide (CO) content of the ambient air. The method is applicable to the determination of carbon monoxide concentrations from 0,6 mg/m3 (0,5 ppm volume fraction) to 115 mg/m3 (100 ppm volume fraction). The method has a lower limit of detection of about 0,06 mg/m3 (0,05 ppm volume fraction) carbon monoxide in air.