The panel members are presented with flows that increase by a factor of 2 in odour concentration every time. This is done at least twice per measurement. Every odour abatement system delivers only limited efficiency in terms of odour units. The remaining odour load in the cleaned gases should be reduced to such a level that, after dilution with ambient air, the odour cannot be perceived in a residential or other sensitive area. Calculations using official mathematical models are necessary to predict the dispersion.
Main inputs are emission load, chimney height and atmospheric conditions.
Principle of odour concentration measurements Odour concentrations are determined sensorically. The determinations are carried out by diluting an odorous air sample so many times that half the panel members can no longer distinguish the diluted odorous air from odourless air. The average dilution factor is calculated using a computer programme. Panel members are selected on the basis of their sensitivity for smelling butanol, in accordance with standards developed for this purpose.