Humans Can Detect One Trillion Different Odors

It used to be thought that human noses could only detect around 10,000 smells, although many scientists thought that was probably a bit too low. A new study suggests that number is much higher, that humans can distinguish among 1 trillion different scents. The ability to distinguish between closely related compounds varied from one person to another.
“Ten thousand is kind of pathetic, it’s a pretty low number,” study author and molecular neurobiologist Leslie Vosshall of Rockefeller University told the Washington Post. This study went like this, as the Post noted: 
Using a procedure similar to a hearing exam, in which listeners must try to distinguish between two tones, Vosshall and her colleagues put 26 noses to the test. Each individual was given three vials, two of them containing the same scent, and asked to determine which smell was the odd one out.
After hundreds of these tests on each subject, the researchers assumed that the subjects’ performances would be similar in recognizing all possible smells able to be made in the lab. They extrapolated that the average human should be able to distinguish at least 1 trillion odors.