An odor is any chemical substance, usually dissolved in the air in very small concentrations, that is detected by the sense of smell. The terms fragrance and aroma are often used by the cosmetics and food industry to describe pleasant odors. Odors can be divided into two categories based on sensory perception: unpleasant (foul or aggressive) and pleasant (sweet) odors.
Basic information
“Odor” is the sensation of odorant molecules dissolved in air. Most odors are produced by organic compounds, but inorganic substances such as hydrogen sulfide and ammonia can also be odorous.
The effect of odor can be analyzed in a two-step approach. The first is the physiological phase, the receptors at the stimulus location in the nose sense the odor. Then the psychological phase begins. Stimuli are stimulated and activated by the area of the human brain responsible for olfaction. Therefore, it is impossible to measure the smell objectively and analytically.
The sense of smell is completely unique and the reaction to odors depends on factors such as gender, age, and health status. Smells that people are accustomed to, such as their own body odors, are less perceived than other odors that come from outside and to which they are not accustomed.
For most people, the process of smelling provides some information about the content of a substance. However, flavorists and perfumers can distinguish even the smallest amounts of chemicals in complex mixtures just by smelling them.
Odor analysis In Germany: the concentration of odorants has been measured with a device called an olfactometer since the 1870s.
Measurement: Although there is no completely objective method for measuring odor, it can be measured in various quantitative ways.
For example:
Odorant substance concentration: This is the oldest and most important method for calculating the odor emission rate. In this method, the calculation is based on the concentration of the odor substrate at the origin of the odor.
Intensity of the odor: In this case, a scale that depends on the density of the air is very important. This scale is classified as follows:
Hedonic rating: Hedonic rating is a rating process that starts with very unpleasant odors and goes down to very pleasant. There is no difference between this method and the method of measuring the intensity of the odor.
Types of smell: This test is performed by the person who verbally describes the smell as disgusting, pleasant, dirty, bad, etc. In this method, nothing is needed except a test subject.
Sampling technique: To ensure that the specific air sample is not affected by other odors in the environment, the subject should perform air sampling in an air environment that is virtually free of other contaminants. Air samples are usually held in a sample torch, as the evaluation can only be performed under appropriate environmental conditions. All materials in which the samples are held should be made of odor-neutral materials.
In the course of discussions surrounding the Environmental Protection Act, a number of laws were enacted in response to the question of how best to address the issue of odor releases.
Country Refinery Manual early 1970s, Federal Emissions Control Act 1974 Technical Manual for Keeping the Air Clean, Odor Emission Manual early 1980s to 1998 Advanced technology. While there are hopes of building olfactory sensors to test perfumes, diagnose cancer, detect explosives, etc., electronic noses are still problematic. The complex nature of the human nose and its ability to distinguish the subtlest odors is currently very difficult to replicate.
Odor Measurement Techniques