scope:

Objective

The present guideline is a guide to the determination of odour intensity and hedonic odour tone in the ambient air. The method presented here is only applicable to grid or plume measurements. The general instructions for grid and plume measurements including the performance of a single measurement are given exhaustively in guidelines VDI 3940 Part 1 and Part 2.

With a given odour concentration, the odour intensity or strength of odour sensation depends essentially on the substance and the mixture. By assessing several concentration levels above the threshold at the olfactometer, it is possible to show the intensity curve as the characteristic of this sample. Under field conditions, it is possible to determine the odour intensity in the ambient air at a specific location, but not the associated odorant concentration and the intensity curve as a function of the odorant concentration. When determining the odour impact by field inspection, the determined intensity can nevertheless serve as a basis for comparative statements on the strength of odour sensation in different assessment squares within an assessment area and between different facility-related odours.

To determine the hedonic odour tone, the facility odour is assessed on a sensation scale ranging from "pleasant" to "unpleasant". The hedonic tone depends on the odorant or odorant mixture, the odorant concentration - and hence on the perceived odour in-

tensity - and on the odour panel member's personal background experience. Here again, under field conditions it is not possible to determine the progression in hedonic tone as a function of odorant concentration levels above the threshold as a means of characterizing the facility odour.