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Odour Threshold
An odour threshold is the odour concentration at which a defined human response occurs — either noticing that something is present, or being able to identify what it is. WikiOdour documents four related threshold terms: Detection Threshold, Recognition Threshold, Individual Threshold and Group Threshold. This page explains how the four relate to each other before you read the individual entries.
Two different questions
Every threshold on this wiki is really answering one of two separate questions about the same odour sample.
- Can it be detected? This is the Detection Threshold (DT) — the concentration at which a sample first becomes noticeable.
- Can it be identified? This is the Recognition Threshold (RT) — always a higher concentration than DT, since identifying an odour takes more information than simply noticing it.
Whose threshold is being measured
Separately, a threshold can describe one specific person or a whole panel.
- One person’s own threshold is their Individual Threshold, which varies with physiology — someone with hyposmia has a measurably higher threshold than a trained panellist.
- A panel’s combined threshold is the Group Threshold. Panel screening keeps panellists’ individual thresholds close enough together that the group can be treated as a single, repeatable figure.
How they combine in practice
Standard EN13725 olfactometry testing works with the Group Threshold at the Detection level: a screened panel is presented with a decreasing series of dilutions, and the concentration at which the group first detects the sample becomes that test’s reference Detection Threshold. Recognition Threshold and Individual Threshold come up more in panellist screening and occupational or clinical settings, where one specific person’s sensitivity is what matters.