SESH · ADVANCED FRAGRANCE ACADEMY
Separate dose, detection thresholds, recognition and perceived intensity.
Follow the route from the nasal cavity to the olfactory bulb. Smell is perception; it does not independently identify a perfume’s ingredient list.
Detection versus recognition threshold
A detection threshold concerns the concentration at which an observer can reliably distinguish odor presence under a specified procedure. Recognition threshold concerns identifying a character. Both are method-dependent and vary between people; a single reported value is not a universal number for every nose, solvent or environment.
High-impact odorants
Some odorants are detectable at very low concentrations, while others require a much larger airborne amount. A minor mass fraction can therefore exert strong sensory influence. Imagine A present at trace level with a powerful character, while B is more abundant but subtle. Odor intensity cannot be used to back-calculate formulation percentages without analytical evidence.
Intensity does not scale linearly
Increasing concentration can alter intensity, but not necessarily proportionally. Receptor responses, adaptation, saturation and mixture masking complicate the relation. With hypothetical observation data, plot concentration steps against intensity ratings to see why doubling ingredient concentration need not double perceived loudness.
These curves show how changing mean and variance affects a statistical model. They are theoretical teaching data, not skin or fragrance-panel results.
Open full-size image ↗Individual sensory differences
Some people detect certain musks or other odorants less readily than others. Experience, current condition and testing environment contribute to variability. One wearer's 'I cannot smell it' is not a universal performance fact. A proper evaluation involves multiple observers, distributions of answers and uncertainty.
Bottle percentage versus airborne dose
One percent in liquid formulation is not one percent in inhaled air. The nose encounters an airborne concentration shaped by evaporation, time and ventilation. Even precise formula composition cannot alone determine perceived impact across wearers and settings. Always label which concentration or measurement is being discussed.
Case: trace versus abundant odorants
Imagine a minor component A dominating the opening while a more abundant B provides a subtle later texture. Different odor impact and release behavior can explain the impression without implying a wrong formula. This is a hypothesis, not proof without testing.
Practical desk-based exercise
Sketch three illustrative graphs: material loading, perceived intensity on a 1–5 scale and the fraction of observers who detect an odor. Explain why their shapes need not match.
Three diagrams summarizing the lesson
Two threshold concepts
- Detection: is anything present?
- Recognition: what does it smell like?
Nonlinear intensity idea
- Lower dose
- May still be readily detected
- Doubling dose ≠ doubling intensity
Keep variables separate
- Liquid concentration
- Airborne exposure
- Observer sensitivity
- Mixture context
Scientific terms
- Detection threshold
- Test-dependent level at which odor presence is detectable.
- Odor impact
- A material's sensory contribution in a specified context.
