Can Dogs Smell Through Aluminum Foil?

Aluminum foil is most commonly used in cooking, comes on a roll, and is a flat sheet of metal foil. So, if you wrapped a substance up in foil, can a dog still smell it? 

You would think that since metal is not a porous material, this would make it a great substance for masking smells. However, things aren't that straightforward with aluminum foil. For one thing, it's often rolled extremely thin, which introduces micro-flaws which can allow odor molecules to pass through. Secondly, folding the foil introduces tiny cracks or fissures, which, again, lets those evasive odor molecules slip from one side to the other. And thirdly, a foil-wrapped package is not the same as an air-tight package. If air can leak out, then so can a smell. 

To answer the question "Can dogs smell through aluminium foil?", the answer has to be yes. 

Dogs from the scent-hound breeds, such as Beagles and Bloodhounds, just love to follow a scent. Indeed, they can be so focused on their noses that they're often deaf to their owner's frantic recall. Those owners are all too familiar with that nose glued to the ground posture which means the dog is onto something interesting. 

Actually, dogs have different sniffing patterns depending on whether the odor is faint and some distance away, or intense and need localizing. 

For the faint smell, the dog moves around a lot, often zig-zagging from side to side. They take lots of rapid shallow sniffs, sampling the air. This combination allows the dog to work out in which direction the smell is strongest, and move toward it. 

Once close to the object, the dog slows right down. They move in a more considered manner, taking fewer but deeper breaths. This allows them to sample the air more carefully and read the subtleties of the signal which helps them pin the object down. 

During the hunt, the dog is usually focussed and alert, with a tail held high as a sign of their enjoyment and committment to the chase. 

For as long as our four-legged friends have lived alongside us, so we've been making use of their sense of smell. Go back 10,000 years when man and dog first hooked up, and those four-leggers would use scent to track down prey. This could mean the difference between primitive humans having a full-belly or starving. With the stakes so high, it is inevitable that the dogs with the best sense of smell would be highly prized and used to breed the next generation of dogs. 

Moving forward in time, the ruling lords prized hunting for sport and entertainment. The sheer luxury of hunting for sport was a sign of their wealth, and so a dog that was fleet of foot and good at tracking a scent was worth a lot of money and a big status symbol. 

In more recent times, a dog's ability to track scents has been used to find people stuck in avalanches or track missing children. So whilst mankind has made use of the dog's awesome ability to track for centuries, it's relatively recently, in the past fifty years or so, that they've been used specficially to sniff out illicit substances or explosives. 

Those very first sniffer dogs were used by the US forces in World War II. Dogs were trained to detect unexploded bombs, and were so successful that they saved many human lives. From there, dogs went on to be trained to sniff out anything from drugs to cancer, with great success. 

Dogs have incredibly sensitive noses. Indeed, their sense of smell is so acute that if our eyesight was as good as a dog's sense of smell, we would be able to see objects perfectly at a distance of 3,000km. 

This amazing ability is down to the sheer number of olfactory receptors inside the canine nose. The nose itself contains scrolls of fine bone covered in mucous membrane packed with those receptors. When the dog breathes in, air is drawn over that membranes so even a few scent molecules will register. 

The information from the olfactory receptors is passed up to the brain, where an extra large processing center awaits. Indeed, the part of the brain that makes sense of scent signals is thousands of times larger in the canine brain than in the human. All of which means dogs are easily able to pick up scents. 

Now, let's look at the aluminum foil side of things. As a fine layer of metal molecules, aluminum foil is not considered porous or 'leaky'. However, this assumption relies on the foil being of sufficient thickness (many regular domestic foils aren't) and the structure of the metal sheet being flawless. 

General domestic aluminum foil just has to meet the needs of a cook and therefore isn't made to be flawless. It is often made with natural microscopic cracks and flaws, which allow scent molecules to escape. If the smell can get out, then a sniffer dog can detect it. 

Then there's the fact that a package wrapped in aluminum foil isn't airtight. Again, this gives odors a chance to migrate out along the fold lines, and be detectable to the dog. 

Okay, it might take a sniffer dog a while to track down the smell, but a good dog will do just that before too long. 

A detection dog trained to pick up the smell of a specific substance does not need additional training to smell through foil. A trained sniffer dog zeroes in on even the faintest odor, no matter what the object is wrapped in. So to train a dog to smell through foil is a story of basic detection dog training. 

Training a dog to hone in on a specific smell is taught using reward based methods. The idea is that the dog associates a certain smell with getting a reward, making the whole exercise into one big game for the dog. 

Basic detection is often taught using a simple game of tug. Initially the dog plays with a clean, unscented towel as a tug toy. Then a second towel that is impregnated with the odor of the item to be tracked. 

The dog is offered a choice of the clean or unscented towel, but only rewarded when they pick the scented one. Thus, they start to learn that he needs to find a certain smell to get his game. 

The training becomes progressively more challenging, with the dog required to pick one scented towel from amongst several clean ones. His reward is then an enthusiastic game of tug with that towel.

Once the dog gets the hang of selecting a specific towel, then the handler starts to place the towel just out of sight, so the dog has to use their sense of smell to find it. The handler then encourages the dog in this pursuit, in a canine game of 'hotter' and 'colder'. The dog is also encouraged using a cue word such as "Find" that they then link to this game of hide-and-seek. 

Ultimately, when the handler uses the cue word, the dog knows there's a good game of tug waiting when they find the scented object.