A comparative study of real-time monitoring detection and active sampling measurements in evaluating exposure levels to ammonia.

Occupational exposure to ammonia is an important issue in the waste management sector, especially in composting and anaerobic digestion plants. In this sector, operators can be exposed to high contents of ammonia which is important to assess. The aim of this work was to provide a comparative study of two ammonia measurement techniques in the workplace air. The first one is an offline active collection of air samples that are then brought to laboratory for analysis and whose results are comparable to OELs. The second one involves real-time monitoring which is easy to deploy, allows for data to be processed both quickly and directly and to explain exposure peaks relative to workers’ activity. These two techniques were simultaneously deployed in several anaerobic digestion-composting plants to assess operators’ potential exposure to ammonia, and data were compared. Results show that there are linear correlations between concentrations obtained from both methods, with a trend to overestimate real concentrations in ammonia for several real-time detectors. This trend could however be explained by the time needed for exposure peaks to decrease. Real-time gas detectors, if cautiously used, are good investigation tools to quickly confirm or invalidate the presence of ammonia in the workplace atmosphere, and for both studying and optimising the workplace. The combination of both online and offline methods facilitates the analysis of a work area or station in order to improve the efficiency of prevention measures and to provide an accurate quantification of operators’ exposure for compliance checking of OELs.