The inability or decreased ability to perceive an odour as continued exposure to that odour increases over time. An odour may initially be strongly detectable but may diminishes completely in a few minutes. Hydrogen sulfide is an example of a chemical that emits a rotten egg smell, but depending on concentration and exposure time, the rotten egg smell will no longer be perceived even though it is still present. Olfactory fatigue is not desired during olfactometry analysis or ambient odour monitoring. In the “EN13725 standard”, are allowed for a series of measurements during olfactometry analysis.
During ambient odour monitoring, it is desired to provide rest periods in neutral environment compared to the one odor is present if possible. An example may include a vehicle, which may act as a separate environment to the one ambient odour monitoring is taking place. Perfumeries use coffee bean odour to ‘reset’ the olfactory sense. Also, having neutral odourless air to be smelled for a few minutes may help reset the olfactory sense.
see the Olfactory Fatigue for more information.