Our noses, as powerful as they are, can also easily become tired and oversaturated, meaning we need to approach smelling sessions with some caution and advanced planning.
Many master perfumers (with the luxury of time on their side), will not evaluate more than half a dozen new samples in a day, for risk of missing fine details or changes in their formulation from one ingredient to the next.
Probably the most important rule to remember, is that the process of smelling actually happens inside the brain, not your nose! So what this means is that you should be drawing in small short sniffs of the aromatic material, then removing it out of proximity of your nose and letting your brain do the work. Hard or long sniffing will lead to satiation of the olfactory bulb and sensory fatigue much much quicker and should be avoided.
The warm exhale or ‘dog breath’ technique - Have you noticed that when dogs sniff out something they normally follow a process of strong, audible nasal exhalations. This warm exhale excites any active odour molecules and makes them easier to perceive. You can do this too. Gently exhale onto a scented blotter and then gently inhale.