The terms ‘assessor’ and ‘panel member’ are used in the EN13725. An assessor is a person who participates in odour measurements. A panel member is an assessor who is qualified to judge odour samples in dynamic olfactometry. An assessor is selected to be a panel member once a specific sensitivity range with respect to the reference odorant n-butanol is demonstrated. They must be able to detect N-butanol at 20 to 80 ppb, which is considered the “norm” of olfactory sensitivity.