Assessment of Uncertainty of Benzene Measurements by Radiello Diffusive Sampler

The uncertainty of benzene measurements obtained by the analysis of thermally desorbable Radiello diffusive samplers was evaluated according to the recent standard EN 14662-4 (2005). Considering the results of laboratory experiments, all the sources of uncertainty regarding the diffusive sampler method characteristics were accessed for the sampling times of 7 and 14 days. The major part of the uncertainty budget (> 79 %) was explained by the variation of the sampling rate due to the environmental factors (temperature and concentration level). For weekly sampling, the diffusive sampler method satisfies the data quality objectives of the European Directive to supply the indicative measurements as well as the reference measurement, since the expanded uncertainty is found lower than 25 %. Using a model-predicted sampling rate which depends on the concentration and temperature, the expanded uncertainty is significantly decreased. The Radiello sampler was found to give correct results for weekly sampling provided that the range of benzene concentrations remained between 0 and 10 µg.m-3, which is generally observed in ambient air monitoring. For 2-week sampling, the expanded uncertainty of measurements exceeds 30 %. However, this diffusive sampler can still be used to carry out an objective evaluation of benzene (minimum quality objective for the accuracy of 100 %). Therefore, the performance of this diffusive sampler method appears to be suitable for the benzene monitoring in ambiant air.JRC.H.4-Transport and air qualit