It is amazing how humans can see colors. As we look around, our eyes take in every color, so many colors. If we are outside, here in Big Bear, we take in how blue the sky is, whiteness in the clouds, the green trees, dirt is brown, roads are black, bark is brown, stop signs are red, lake is green (in some places), and so forth. Imagine the colors you would see in a home, so many, too many to mention. I think you get the idea. Vision is such a great blessing.
When humans smell, no matter how many different aromas are in the air, we smell the one that is the strongest in many cases. The prevalent one wins. As we are blessed with vision, we are limited in smell.
Now, if we reverse the difference in these two, from eyes to nose, relating to a dog, you will start seeing the picture through the nose. A dog uses its nose as we see with our eyes. All those colors are basically seen through a dogs nose. No matter how many aromas or smells are within the reach of a dogs nose, they can smell all the odors in their nose as we seen colors in our eyes.
This is why dogs are used for narcotic and explosive detection. No matter what you try to conceal the odor of marijuana with, such as coffee beans, a dog can smell all at the same time, the coffee beans, plastic wrapping, all odors in the vehicle such as dirty laundry, kids plastic toys, cigarette butts, gas fumes, carpet and last but not least, the odor of marijuana.
Dogs see as well with their noses, as we see with our eyes.