Comparison of trip average in-vehicle and exterior CO determinations by continuous and grab sampling using an electrochemical sensing method

Abi Esber, L., El Fadel, M. and Shihadeh, A (2007) Comparison of trip average in-vehicle and exterior CO determinations by continuous and grab sampling using an electrochemical sensing method. Atmospheric Environment, 41 (28), 6087-6094. (doi:10.1016/j.atmosenv.2007.05.020).

Abstract

In air quality monitoring studies, continuous sampling is capable of reflecting real time variation of gas levels, however, with a margin of uncertainty related to the response time of the sensor and to the speed of concentration fluctuation. In contrast, grab sampling allows the determination of average gas concentration over the whole sampling period eliminating thus the uncertainties associated with the continuous method. As studies of in-vehicle carbon monoxide (CO) exposure often show rapidly fluctuating CO levels and are increasingly using the continuous electrochemical sensing method, the present activity aims at validating the suitability of the latter method for this monitoring task. For this purpose, an electrochemical CO sensing monitor was used to continuously monitor CO level inside and outside of a vehicle moving in an urban area, and to analyze the content of concomitantly taken grab samples. Trip-average CO levels measured using the two testing methods were compared. For CO levels higher than the instrument detection limit (1 ppm), the observed percent difference between continuous and grab sampling results varied within a fairly acceptable range (0.6–15.4%). The regression of continuous sampling data against grab sampling data revealed an average error of 6.9%, indicating the suitability of the continuous electrochemical method for monitoring in-vehicle and exterior average CO concentration under typical urban traffic conditions.

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