Moths, for example, can detect pheromones from other moths for several miles downwind. But pheromones are generally defined as chemical signals between animals of one species. The human snout may have two separate structures for detecting chemicals in the air. Keeping in mind the fact that human pheromones may or may not actually exist, let's keep looking at this animal communication system. Odors are detected by the olfactory epithelium, a group of nerve cells located deep inside the snout.
Odors seem more various than pheromones.
But it may have 10 times as many receptor types in its olfactory epithelium, where the sense of smell starts. We know we're smelling burnt rubber when a muscle car leaves a stoplight. We know we're smelling coffee when we wake up and smell the coffee. After reading that list, please remember that there's still considerable question about whether people actually respond to pheromones, but we'll talk with the doubters later.