Individuals differ considerably when rating the perceived properties of odors, especially over time. A second glance at previously published data-sets from our laboratory revealed that the same invariant exposure often produced both floor and roof effects. An odor that at the end of the exposure ses-sion was regarded as non-existent by one participant, could border the “absoulte maximum” rating category in another. We provide re-analyses from four exposure studies where we illustrate the perceptual variability over time, and outcomes associated with such ratings. We note that high, compared with low ratings of odor intensity over time is associated with ratings of unpleasantness and symptoms, but also with everyday distress, cognitive performance, autonomous nerv-ous system activity and deviating responses in the so-called pain or saliency matrix of the brain. We bring an open ques-tion to ECRO regarding how this considerable variability should be interpreted, and what the consequenced are for research and for setting exposure limits.