How Many Scents can Humans Distinguish?

Humans can detect more than 10,000 different scents. There are hundreds of olfactory receptors in the human nasal passage, and each has its own gene and recognizes different scents. The reason some people can't smell a particular scent, such as camphor or the sulfur compound in asparagus that makes urine smell funny, is because a particular gene is damaged or missing.

More Smelly Facts:

• One of the animals with the best sense of smell is the dog, of course. A dog's sense of smell in general is anywhere from one hundred thousand to a million times better than a human's. The bloodhound breed, however, has a sense of smell nearly a hundred million times better than a human's.


• The bear, however, can out smell any dog — the bear's sense of smell outranks even the bloodhound by seven times. A bear can smell food as far as 18 miles (29 kilometers) away.


• Not all creatures use noses to smell. Insects, of course, use their antennae. Lemurs, on the other hand, carry their scent glands on the top of their heads.


• The marine animal with the best sense of smell is the shark — it can smell blood, for example, in a diluted ratio of 1 part blood to 100 million parts water.