There are many chemicals that cause odor. However, it is not possible to measure the effect of an odor on physical sensors. In fact, only the human nose is considered to be a powerful sensor for evaluating odor. The human nose 10-19 has an odor detection limit of mole level. Most chemical detectors are not as sensitive as a human nose.

The perception of odor does not depend on the amount of substances that create this odor. The effect of an odor on people's sense of smell varies depending on the following two factors:

• Which chemicals cause odor
• The ratio of these chemicals together

The common characteristics of fragrances are:

• The substances that create odor cannot be determined by analysis.
• It is not possible to establish the relationship between the intensity and intensity of the fragrance by detecting the main components of a fragrant mixture.
• Technologically developed sensors cannot distinguish between pleasant or unpleasant odor

The olfactometer is a device used to measure odor intensity. Technically, olfactometry is a method of introducing odorous gases to the human nose at controlled concentrations and measuring the effect of this odor on the sense of smell.

Olfactometry method is based on two basic principles:

• Presenting a defined smell to the human nose at a certain intensity and measuring the effect of the smell (this principle means calibrating the ability of the human nose to smell)
• Using the human nose as a detector and detecting unspecified odor intensities

The results obtained by the olfactometry method are mainly used in the following areas:

• Modeling the distribution of odorous gases in air
• When calculating expected odor imitation values
• The measured odor intensity is placed on a scale ranging from unnoticeable odors to very strongly noticeable odors (as a result the intensity of an odor depends on the source of the odor).
• When determining the hedonic quality of the fragrance (whether a fragrance is pleasant depends on the source of the fragrance, and depending on the intensity of the fragrance, a fragrance can be a pleasant fragrance at low intensity, while a fragrance can be a disturbing fragrance at high intensity).

Three different parameters are used to determine the character of the odor source when measuring with olfactometry method:

• Density of concentration (concentration)
• Sensation of odor (seven levels from unnoticed to very severe)
• Quality of odor (from pleasant to unpleasant 9 level)

The following steps are generally taken when olfactory odor testing:

• The measurement team consists of the 4 panelist and a measurement leader (these people need to be sensitive to odor)
• The measurement leader determines the dilution stage of the fragrant gas presented to the panelists
• Leader delivers a surprisingly diluted gas to every panelist
• Panellists react when they smell
• Odor tests are computer controlled
• Odor levels of panelists are determined according to odor detection levels
• The results are evaluated statistically by computer program

Odor tests are performed by olfactometer by authorized test and inspection institutions.