Smell

Olfaction, also known as smelling, was a method of detecting chemicals and one of the five senses of human beings. (TV: The Evil of the Daleks) The quality detected was called an odour.

Different types of creatures used different organs to smell; humans used the lining of their noses, insects used their antennae and Myxilinic frost-worms smelled from above the central mouth. (PROSE: The Colour of Darkness) Though their olfactory system was similar to a human's, the Gallifreyans could do a chemical analysis of the air using their sense of smell. (PROSE: Doctor Who and the Carnival of Monsters)

In many species, like humans, the olfactory system used the same parts of the brain as memory and emotion. This was a weakness that the Dreamspinner, Shas-Raklat, exploited by changing the Karagulan's perception of events in order to abduct their children for spare sensory parts. (PROSE: The Colour of Darkness)

Pungent smells could indicate poison or toxicity. (PROSE: Wish You Were Here) Some species, like Raxacoricofallapatorians or the Ameteli, could be identified by their distinct smell signatures, like bodily gasses or calcium decay. (TV: World War Three, COMIC: Love is in the Air)

Smell of time
The Ninth Doctor claimed that time had a smell. For instance, Rose Tyler's time, 2005, smelled of diesel, hair gel and satellite trails. (PROSE: Rose and the Snow Window) The Tenth Doctor claimed to have deduced that he and Donna Noble were in the 1920s from smell alone. The 1920s apparently smelled of grass and lemonade, with just a hint of mint. (TV: The Unicorn and the Wasp)

The Thirteenth Doctor could also smell the effects of time travel on someone who had been through the Time Vortex. (COMIC: A New Beginning)

A time puncture leading to 1812 St Petersburg smelled, to Rose Tyler, of greasy candle smoke. (PROSE: Rose and the Snow Window)

Memories
While living on Bannerman Road, Sarah Jane Smith still recalled the smell of vanilla from a garden in San Martino in 1492. (TV: Death of the Doctor)