Dogs are intelligent animals that rely heavily on their nose and eyes to help them navigate and understand the world. A dog's sense of smell is said to be a thousand times more sensitive than that of humans. In fact, a dog has more than 220 million olfactory receptors in its nose while humans have only 5 million. Many dogs enjoy putting their heads out the window to enjoy the sites and smells of the passing world. As your vehicle is driving, the fast moving air brings a constant stream of scents which is very interesting for your dog and provides him with key information about the surroundings. This fast moving air also has a cooling effect by speeding the evaporation of saliva from the tongue and mouth of a hot and panting dog.

While enjoyable for your dog there are risks to hanging his head out of the window. Flying particles, stones, and debris may cause injury to the eyes. It is not uncommon for dogs to jump out of a moving vehicle, even if they have never done so before, if they catch a particularly interesting sight or smell. Also, it is not recommended for your dog to have his head out of the car window for the same reasons that it is not recommended to hang your arms or legs out of a car window - if you drive too close to an object or a car passes you to closely, this could result in a serious or deadly accident for your dog.