Sniffer Dogs – How do they sniff out drugs?


A dog’s nose is reputed to be at the very least 10,000 times more sensitive to smells than human nose.
The sense of smell is the dominant of a dog’s senses followed by hearing and sight.

Though dogs have been used around the world for security with references dating back to the Roman army of being used as attack and sentry dogs, it is only in the last century that they have been adopted as an indispensable asset of police and military operations worldwide.

Notwithstanding the use of dogs for tracking, the recognition and utilisation of the canine sense of smell for a wide range of disciplines is relatively new and demand for detection dogs of recognised breeds outstrips supply.


Sniffer dogs are used to search for survivors trapped in buildings after earthquakes, find live and dead people in open fields in disaster areas, detect cancer melanomas, search for termites, incidences of bedbugs and invasive pests, drugs, explosives and minute traces of accelerants in arson investigations.
They are trained to detect live and dead bodies in lake and coastal areas and retrieve them and are even used to detect burst underground water mains.

There is a high demand for detection dogs and though there is a widespread use in so many areas, the prevention of terrorism puts explosive detection dogs at the top of the list worldwide closely followed by drug detection dogs.

On June 21st 2019 Philadelphia police discovered nearly 16.5 tons of cocaine with the assistance of drug detection dogs on a ship en route from Chile to Europe. The street value of the confiscated drugs was over $1Billion dollars and consisted of fifteen thousand bricks, which if laid end to end would cover a distance of two and a half miles. It was the biggest discovery ever made in the USA.


Dogs in demand for drug detection work include English Springer Spaniels, Labrador Retrievers, Golden retrievers, the Belgian Malinois, German Shepherd dogs and Border Collies.

The U.S. imports between 80 and 90 percent of it’s working dogs from Europe, which has a rich heritage of dog trials and competitions for breeding and training dogs for police and military roles .

Some dogs are geared to dual-purpose work i.e The Belgian Malinois and German Shepherd dogs ( also known as Alsatians ) are easily recognisable as deployed in patrol, protection and attack roles as well as in drug detection.

Dogs such as the English springer spaniel, known as being ideal family pets are excellent drug detection dogs.

In civilian environments, they are accepted positively and without the wariness or apprehension that may be associated with the “he looks fierce, does he bite ?” German Shepherd or guard dog stereotypes.


A sniffer dog’s nose has been finely tuned to be particularly sensitive to particular substances.

A K9 Deployment drug detection dog has been trained to detect traces of the full range of illegal Class A and Class B drugs.

On the street, across the world, the various drugs have a bewildering array of alias’s some of which, if you were asked to identify, could get you confused with a breakfast cereal, a household pet, something to cool your drink with or exercise in a paddock.


Drugs commonly used for experimental, recreational and dependency purposes ( and their alias’s):

Amphetamine – also known as Amphetamine Sulphate, Base, Billy, Paste, Sulph, Whizz
Cannabis Resin – also known as Boom, Gangster, Hash, Hashish, Hemp
Cocaine – also known as Blow, Bump, C, Candy, Charlie, Coke, Crack, Flake, Rock, Snow, Toot
Heroin – also known as Brown Sugar, China White, Dope, H, Horse, Junk, Skag, Skunk, Smack, White Horse.
Ketamine – also known as Cat, Valium, K, Special K, Vitamin K
Marijuana – also known as Blunt, Bud, Dope, Ganja, Grass, Green, Herb, Joint, Mary Jane, Pot, Reefer, Sinsemilla, Skunk, Smoke, Trees, Weed
MDMA (Ecstasy) – also known as Adam, Clarity, Eve, Lover’s Speed, Peace, Uppers
Methamphetamine – also known as Crank, Chalk, Crystal, Fire, Glass, Go Fast, Ice, Meth, Speed


Dogs have an amazing set of attributes, they have a great sense of smell and, some breeds more than others, a strong desire to hunt.
If well managed they are intensely loyal, creating strong bonds with their handlers, are obedient, responding well to training and can work in intensely stressful environments.

While a sniffer dog is on a drug search, he can cover a lot of area very quickly. It would take human officers 10 times as long to search the same area, and they’d still never find everything a dog can sniff out.

In 2002, a drug detection dog foiled a woman’s attempt to smuggle marijuana into a prison in Brisbane, Australia. The marijuana had been inserted into a balloon, which was smeared with coffee, pepper, and petroleum jelly and then placed in her bra.


The olfactory epithelium is a specialised tissue inside the nasal cavity, containing olfactory receptor cells, which have cilia extensions. The cilia trap odour molecules as they pass across the epithelial surface.

In humans, this tissue measures around 10 cm2 and lies on the roof of the nasal cavity about 7 cm above and behind the nostrils and is the part of the olfactory system directly responsible for detecting odours.

.In dogs, by comparison, it measures 170 square centimetres of tissue. The processing of all the scent related information is done by the olfactory lobe in the brain, but the dog’s lobe is around 40 times larger than that of humans.

The size and complexity of this structure in the brain is one reason that dogs have a natural aptitude to detect drugs, bombs, banknotes, bed bugs, cancer, and track missing people by their individual scent, but more-so to negate other intrusive odours occurring naturally or placed by intent that are significantly stronger.


When a dog breathes in, the air separates into distinct paths, one flowing into the olfactory area and the other passing through to the respiratory system the lungs.

When we breathe, we use the same route within our nose for inhalation and exhalation. In doing so we stop smelling during exhalation and recommence on inhalation.

Dogs also have the ability to detect different smells from each nostril, it’s as if the dog’s nose was in stereo.

When a dog exhales, the air exits through slits in its nose whilst air is still incoming through it’s nostrils. As a result, the uninterrupted flow of incoming air through the dog’s nose provides continuity of odours aiding it’s perception of odours and maintaining traction of a pinpointed scent.

In a study conducted at the University of Oslo in Norway, a hunting dog holding its head high into the wind while in search of game sniffed in a continuous stream of air for up to 40 seconds, spanning at least 30 respiratory cycles.

Depending on the level of activity and exertion and if operating under stress the breathing pattern of dogs changes.

When we go for a run it is a short interval between only breathing through our nose and progressing to inhaling hard through our mouths as well.

On an increasing scale of activity, the dog will breathe in the following sequence.

  • Inhalation and exhalation through the nose.
  • Inhalation through the nose exhalation through the nose and the mouth.
  • Inhalation through the nose and the mouth and exhalation through the nose and the mouth.

A dog’s main method of cooling its body is panting as they do not possess sweat glands.

Dogs can either pant or sniff, but they cannot do both at the same time so sniffer dogs have a reduced olfactory efficiency if they overheat as they focus less on sniffing as they attempt to cool themselves down.


It is a well-established fact that female dogs have a better sense of smell than males, which demonstrates a contradiction when the majority of police dogs are males.

The reason for this is two-fold:

1. A female’s sense of smell is adversely affected when she is in heat and thus every six months for a period of 16 to 24 days and possibly some weeks before and after she is, by comparison with a male dog, unreliable.

2. A female dog in heat provides a real distraction to male dogs.

Both of these factors can and are overcome by neutering the females, who subsequently provide no distraction to male dogs, nor inconsistencies in their sense of smell.


The initial training of drug detection dogs and related training can be very expensive. Many hours of hard work go into training and preparing the K9’s for the many different scenarios they will encounter in “active” duty.

  • There are established breeding and training kennels that train detection dogs.
  • The breeding school will breed and train the dogs in the various disciplines.
  • Detection dogs as a general rule either detect explosives or narcotics, but not both.
  • When the detection dog is first united with it’s handler, the real work begins to become an effective team.

As a sniffer dog is trained on a daily basis the level of difficulty is increased in line with its achievements and benchmarked progress, to finely hone its skills in detecting and identifying odours.
The aim of training a dog to identify odours is to teach him to make optimum use of his innate talents and hunting traits in order to meet the human needs and objectives.

Depending on the discipline the dog is involved in: guarding, patrolling, tracking or search, it is trained accordingly and in line with the working environment.
Studies have shown that detection dogs working in hazardous high-intensity environments do adapt and focus on their objectives.
Dogs trained in drug detection have no interest in the actual drugs themselves, and it would be hard to imagine a dog that liked explosives or finding corpses in earthquake situations.

They are actually looking for their “reward” in achieving the task given by their handlers.


The drug detection dog discipline is split into two main fields, Passive and Pro-active.

The pro-active dog does not merge with the public and is therefore permitted a natural indication of a successful find.

Their responses can be very vocal with barking and overtly demonstrative behaviour, pawing the ground or straining on the leash.

If you take the case of dogs trained to detect explosives, then the focus is aimed at detection and alerting the handler with no attempts to dig out the “prize” and claim the reward.

Similarly with dogs that work in drug detection especially in public environments such as airports, schools, college and university campus’s, events held at racecourses and festival venues and licensed premises, the “alert” signals to the handler are passive and in the instance where drugs are detected the signal might be for the dog to simply sit down quietly next to the person of interest.

Having an English Springer Spaniel or even a taller gun breed dog (used to detect drugs on the upper body) that has detected traces of narcotics simply sit down quietly next to a suitcase or a person is regarded as working in passive mode.

Sniffer Dog training is not just about obedience and drug or explosive detection, but also about improving and maintaining health, stamina and physiological conditioning and a good regime and diet impacts on the olfactory performance.

English Springer Spaniel training

Sniffer dog detection rates are impacted by periods of challenging exercise.

Well trained sniffer dogs with improved cardiovascular conditioning demonstrate a lower exercising heart rate.
This is turn elevates thermoregulatory performance and reduces the need for panting.

Studies conducted between well-conditioned and non-conditioned detection dogs showed a 63.6% decrease in olfactory sensitivity in the latter.
Even dogs with a natural propensity for sniffing things out need training and regular refresher courses regardless of whether they are working in the field or not.


Dogs trained in drug detection have no interest in the actual drugs themselves, and it is hard to imagine that a dog that likes the smell of explosives or corpses in earthquake situations.

Success is rewarded by their favourite toy

Dogs have the ability to perform better under the supervision of experienced handlers and the role that the handlers play in the interaction with the public cannot be underestimated whether it is at a public event, an airport or busy transport environment, a school, college or university or a late-night licensed premises.

The person doesn’t have to carry drugs for the scent to be detected. The dog can smell if someone has been in close contact with drug users, for example at a party where Marijuana was smoked. The drug sniffer dog is taught to react passively to the person who smells of drugs.

All K9 Deployment sniffer dogs and handlers are trained and accredited to ACPO (Association of Chief Police Officers) standards at a Regional Police Dog Training Centre or trained and accredited by NASDU (National Association of Security Dog Users).

This includes initial, refresher and continuation training with accreditation annually. All our dog handlers are SIA (Security Industry Authority) licensed.

Wild canines tend to have a better eyesight than domesticated dogs

They are actually looking for their “reward” in achieving the task given by their handler who is also their best friend.

In one documented incident a drug sniffer dog was patrolling cars at a customs crossing point. It managed to slip its leash and ran amongst the queuing vehicles.
Before her handler could find her, she trotted back into view, holding a large brick of marijuana in her jaws.

Although the police could not tell which car the drugs came from, the dog still got her reward and the drugs were confiscated.

Professional detection dogs typically stay assigned to the handler that they have trained and bonded with and this is the foundation of a successful partnership.


Dog handlers identify with and interpret the behaviour of their dog.
There is as much focus on training the dog and handler to work together as there is in training the dog in detection and response.
The dog is alert to and cognizant of the handlers body stance, commands and cues.

Similarly the dog handler reads the behaviour of the dog which in many instances has proven to have prevented the handler from coming to harm through the sensitivity of the dog to danger in it’s surroundings.

Search and Rescue Dogs sense the dangers of collapsing buildings almost faultlessly, alerting their handlers to the danger.

The behaviour of dogs before during and after earthquakes is well documented throughout the ages where they would become agitated and evacuate buildings prior to earthquakes.

Geologists at the University of California measuring earth tremors that could only be detected by their equipment but not felt by themselves found that every incidence of a tremor was preceded each time by the continuous barking of dogs.


The hearing ability of dogs is far superior to that of humans.
The apparently silent whistles used in whodunnit murder mysteries and demonstrated at sheepdog trials are to dogs a siren.

The audible range for humans is 20Hz to 20,000 kHz but dogs, dependent on age and breed is usually in the 67Hz to 45 kHz frequency range.

The consequences are that a dog can hear and identify the unique walking gait of his owner and even the specific engine murmur of his car, readily distinguishing between, and alert to, the approach of the postman or neighbourhood burglar.


Dogs have superior night vision to humans and are very sensitive to motion, moreso than static objects, making them good as night-time watchdogs. Predator species like dogs (and humans) have eyes set close together.

Dogs, depending on the breed are usually set at a 20 degree angle increasing the field of view and the peripheral vision.

Humans with 20/20 vision are said to have perfect eyesight which means that we can distinguish letters or objects at a distance of 20 feet.

Dogs typically have 20/75 vision which translates to a dog standing 20 feet away from an object being able to see what a human being can see standing 75 feet away from it.
Labradors who are identified as good drug detection dogs are also a breed that tends to be an exception and are bred as they have much better eyesight and may have vision that is closer to 20/20.

Conclusions reached in 1960 by Doctors R. and R. Menzel concluded that the eyesight of a domestic dog may be dull relative to it being a house pet, whereas wild canines have an excellent sense of sight: a study which supported the earlier findings in 1954 in a study by Professor H. Stephan.