individual perception threshold (IPT)

in atmospheric chemistry
https://doi.org/10.1351/goldbook.I03014
A term used in odour testing which signifies the lowest concentration of a particular species at which a subject indicates both an initial positive and repeated response.
Source:
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2196 (https://doi.org/10.1351/pac199062112167)