Human can detect around 1 trillion different smells.
Bushdid et al. reduced the complexity by investigating only mixtures of 10, 20, or 30 components drawn from a collection of 128 odorous molecules, this astonishingly large number is probably the lower limit of the potential number of olfactory stimuli that humans can distinguish.
Range for smell:
- Human ~ 1m
- Dog ~ 100 m
- Elephant ~ 3 km
- Moth ~ 5 km
C. Bushdid, M. O. Magnasco, L. B. Vosshall, A. Keller "Humans Can Discriminate More than 1 Trillion Olfactory Stimuli", Science 21 March 2014: Vol. 343 no. 6177 pp. 1370-1372