Odor Threshold

By Tabitha Mishra
Last updated: October 17, 2021

What Does Odor Threshold Mean?

The odor threshold is the first concentration at which an airborne chemical becomes detectable by smell to a typical person.

This concenpt is relevant to chemical safety, since chemicals with strong odors can be readily detected by the smell they emit. This makes it easier to identify chemical leaks or the presence of hazardous substances in the atmosphere.

Chemicals with weak odors, on the other hand, are more difficult to detect without specialized instruments.

Safeopedia Explains Odor Threshold

While smell is not a reliable method of detecting chemical leaks, it can nevertheless act as the first warning sign. However, this is only the case for chemical concentrations that reach or surpass the odor threshold.

The odor threshold is necessarily an approximation, since olfactory perception varies among individuals. It can, moreover, vary depending on the conditions of the location and whether there are other pronounced odors that might mask the smell of the chemical.

If a job requires the use of chemical compounds with noxious smells, employers are encouraged to replace them with less odorous chemicals where possible. The constant presence of these srong smells can lead to olfactory fatigue, which can prevent workers from detecting the presence of a hazardous chemical in the air.

There are two types of odor thresholds relevant to hazardous chemicals:

  • Detection threshold: The lowest concentration of the odorant that will stimulate an olfactory response
  • Recognition threshold: The minimum concentration of the odorant that is recognized as having a characteristic odor quality by a specific percentage of the population (usually 50%)

Evaluating Odor Threshold Information

Odor thresholds are determined in the laboratory using various methods to dilute odorants, which are then presented to test subjects. A known concentration of odorant is delivered to the subjects and responses are measured. Responses are taken for whether or not an odor is detected, the strength of the odor, and the quality of the odor (pleasant, unpleasant, fishy, or aromatic).

After recording, statistical methods are applied to determine the odor threshold for detection and recognition.

Usually, tests are done on a large number of subjects with a number of trials. Physiological and personal factors such as smoking, drug dependency, gender, pregnancy, and age are considered when selecting the test panel. Smokers are generally excluded.


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