Abstract

Comparative measurements with two types of CO monitors (Philips PW 9775 and TECO model 48) have been carried out on different locations mainly in the city environment. Measurement were carried out on 7 days resulting in 40 hourly average values. The main findings are: - the relation between the measurement results of the two monitors can be described by a quadratic function with the Philips monitor always showing the lower values in the concentration range investigated (0-9 mg CO/m3) ; - the Philips monitor shows a threshold value of 0.10-0.15 mg/m3 ; - the differences observed are concentration dependent, increase from 0 to higher concentrations and reach a maximum of 0.70 mg/m3 at 7.0 mg/m3 (TECO value). Above 7.0 mg/m3 the differences decrease again. The origin of the deviations of the Philips monitor is not known. However the regression equation may be explained by assuming suggests a concentration dependent conversion of CO into I2 in the converter unit of the Philips monitor.