Comparison of three instrumental methods to monitor nitrogen dioxide

Three commercially available automated NO2-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-hour averages given by the three monitors in the range 0--700 mug NO2/m3 and the comparison of the global statistics for the same NO2-pollution simultaneously seen by the 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 NO2-pollution were in good agreement.