Abstract
In order to draw the right conclusions from olfactometric analyses as well as effectively prevent odour nuisance, taking into account confidence level of odour result is of great significance. Dependence of confidence interval for the expected value of odour abatement efficiency in determined conditions upon the number of observations is presented in The European Standard ‘Air Quality – Determination of odour concentration by dynamic olfactometry’ (EN 13725, CEN, 2003), which enables to plan the exact measurement session and establish the number of measurements to be conducted.
The objective of the research was to determine whether this dependence may also be applied in changing conditions. The effectiveness of six installations was assessed in the process of deodorization of waste gases characterized by the difficult to predict composition. Olfactometric measurements were performed in two large objects: wastewater treatment plant and manufacturing plant. Dry chemical sorption, a water scrubber and four plasma-assisted installations were examined. Nine observations (odour concentration measurements - in the crude and clean gas stream) were carried out for each installation.
The lung principle method was used for sampling, together with the application of dynamic pre-dilution with clean dry air. The measurements of odour concentration, made in accordance with the EN 13725 (2003) standard, conducted by the trained assessors, meet the selection criteria for the olfactory sensitivity. The samples were pre-diluted using the Strohlein olfactometer and odour concentration was measured using the Ecoma TO7 dynamic olfactometer.
The average efficiency of evaluated installations ranged between 9 and 78 %. The number of observations needed to obtain odour abatement efficiency of the desired confidence interval in real, changing conditions can be determined based on the European Standard. Nine observations were considered to be an optimal number of observations used for evaluating efficiency in changing conditions.
