I read some thing about Grizzlies a while back, and it said that they have an unbelievable sense of smell and can smell blood from miles away if wth wind is right.
They also said it was able to pull, with one paw, a dead 700 lb Elk from a deep hole in the ground.
Shudder.
I know a lot more about dogs than I do bear, but one can extrapolate.
A human nose contains about 6 million olfactory receptors over about one square inch (i.e. postage stamp) of tissue. A typical dog has about 300 million receptors on about a square foot of area. If scent were sight, a dog could see things as clearly at 3,000 miles as you or I could see things at 1/3rd of a mile.
I don't know a lot about bears but I do know their noses are a lot bigger than a dogs.