Measuring odors

Smell is a sensation resulting from numerous physical-chemical, memory and cognitive processes. It is therefore essential to differentiate the odor of a gaseous mixture from its chemical composition. Odor must therefore be measured in its own right, with complementary physico-chemical measurements if necessary.

There are two types of measurement: measurements in the emitting environment, i.e. at emission sources, and measurements in the receiving environment, i.e. at neighboring populations.

Odor measurements in the emitting environment consist in assessing odor concentrations, intensities and olfactory quality, according to standardized protocols. They are used to verify regulatory compliance of facilities, prioritize sources, and guide and define the treatment solutions to be implemented.

Measurements in the receiving environment are carried out to quantify the odors perceived by local residents and to characterize the resulting nuisance. Carried out by experts or by juries of local residents, they provide an objective description of odor and nuisance trends, to verify, for example, the effectiveness of actions taken by the manufacturer to improve the olfactory comfort of local residents. They can also be used to establish the relationship between the olfactory perceptions of local residents and the operation of the emitting site, so that solutions can be sought to reduce emissions, by intervening directly in the operating process.

At the same time, odor emission measurements combined with measurements in the receiving environment represent indispensable sources of information for implementing mathematical models to calculate the olfactory impact of a facility, while taking into account the complex phenomena of odor dispersion in the atmosphere. These simulations enable us to meet legislative requirements:

• determining the olfactory impact of future facilities;

• by checking compliance with environmental air quality target values.