The weaker the odour concentration of an air sample, the more does adaptation affect perceived strength. This is because at a lower concentration it may be necessary to sniff harder and to take more than one sniff in order for the odour to be registered. Continuous exposure to an odour should be avoid during testing. Although adaptation takes some time to develop, recovery takes place more quickly. Recovery times may range from seconds to minutes depending upon type of odour, odour concentration and duration of testing.
Adaptation begins to reduce perceived odour intensity and quality during the first inhalation.
In olfactometry testing, the order of dilution steps is ascending, from a weaker strength to a high strength. This procedure is designed to avoid adaptation. It is essential that panelists commence at the optimal dilution step, such as two steps lower than the threshold. The phenomenon of adaptation frequently reveals itself in industrial situations, with workers reporting that an initially repulsive odour eventually seems less repulsive. Anosmia is lack of sensitivity to some groups of odours.