Human nose can detect one trillion smells

The human nose can detect more than one trillion individual smells, billions more than the commonly held figure of just 10,000.

A study, published in the journal Science by US scientists, suggests that the human nose is far more capable than originally thought and able to detect billions more smells than the now seemingly meagre 10,000 smells previously assumed by scientists, as reported by The Guardian.

A team of scientists used a collection of 128 different chemicals to create different odours with varying degrees of similarity and tested if subjects could spot the difference, with each odour containing either 10, 20 or 30 different components.

Participants were then asked to pick the odd one out among three vials containing odours with the same number of components but different degrees of similarity.

While performance varied greatly between the 26 participants, scientists found that while no one could tell odours with more than 90% similarity, at least half of the participants could tell odours apart when the degree of overlap was less than 75%.

Dr Andreas Keller of Rockefeller University, lead researcher of the project, said: “Our study replaces that previous number of 10,000 with a much more realistic and [much] higher number and shows the human sense of smell does have a good capacity to discriminate.”

From the results, Keller and his team worked out the number of possibly detected smells by taking the total number of possible odour mixtures possible concluding that the human nose is realistically capable of discriminating between one trillion different odours made up of 30 components.

Despite their figure dwarfing previous estimates, Keller still believes the result is an underestimation of the abilities of the human nose, pointing toward the fact that there are far more odorous molecules than the 128 studied.