Comparison of three instrumental methods to monitor nitrogen dioxide

Abstract Three commercially available automated NO 2 -monitors, based on amperometry, chemiluminescence and coulometry respectively, were compared under simulated field conditions over a period of 45 days of continuous operation. The main purpose of this programme was the study of the reliability of the overall system, sampling line-monitors-data acquisition and handling system (PDP-8/E), the correlation between the individual half-four averages given by the three monitors in the range 0–700 μg NO 2 /m 3 and the comparison of the global statistics for the same NO 2 -pollution simultaneously seen by three different monitors over a period of 45 days. Based on more than 1200 valid half-hour averages, a highly significant correlation between the different monitors was obtained, while the statistics of the simulated NO 2 -pollution were in good agreement.