About this Article
Written by: Michelle Sivak
Written on: December 1st, 2011
Tags: security & defense, mechanical engineering, electrical engineering
Thumbnail by: Elucidate/Wikimedia Commons
About the Author
Michelle is a junior majoring in Biomedical Engineering at the University of Southern California. She will be graduating in May of 2013, and hopes to be employed at a leading biotechnical company, or to pursue her Ph. D at a professional physical therapy or veterinary school.
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Volume XIV Issue II > The Dog’s Nose Knows…Or Does It? Explosives Detection by Mechanical and Electrical “Noses”
Explosives have been and continue to be a major threat to airports and military personnel across the globe. With the endless amount of information available on the Internet and with technology advancing at an incredibly rapid rate, dangerous weapons have never been so easy to manufacture. Not only are newly made explosives a concern to the world, but unexploded land-mines from decades-past wars are still killing thousands of people each year. Even though rigorously trained canines have been the standard for detecting explosives, technological detection devices may serve as a much less expensive method for preventing deadly blasts.


The canine nose contains 220 million olfactory receptors. This number may not seem very large considering the trillions of cells that compose the bodies of higher organisms such as dogs or humans, but when compared to the mere 5 million olfactory receptors that humans possess, the reason that dogs are so essential to rescue teams, police forces, and defense units around the world becomes evident. Dogs can detect a seemingly endless amount of odors and can even identify odors at concentrations down to parts per trillion, meaning they can identify a scent even if the source of odor is diluted by as much as 1:108 [1]. Intricate nasal anatomy and the highly developed olfactory lobe of canine brains provide dogs with a sense of smell 1,000 times more sensitive than that of humans.
U.S. Navy/United States Navy
Figure 1: A member of the Transportation Security Administration (TSA) conducts a security search for unidentified objects.
Since the mid-1800s, dogs’ noses have been put to work tracking missing people and detecting drugs, explosives, and most recently, some types of cancer [2]. Sniffer dogs are usually used in airports for explosive detection in luggage and on passengers, as well as in the military for rescue and landmine discovery. Training dogs, however, can be quite costly. The Transportation Security Administration (TSA), for example, provides Pittsburgh International Airport with $50,000 per dog per year to cover training and related expenses (see Fig. 1). Additionally, employing these talented animals comes as a package deal, for the dogs work as a team with their handlers, who typically work with the dogs for 6 to 8 years [3]. Although some security specialists remain firm in their beliefs that no technology can “perform as well as the canines do,” the dogs can mistake clean luggage or cargo as hazardous, which can result in the unnecessary, lengthy, and costly evacuation of an entire terminal [4].
As terrorists and militia gain access to more sophisticated and dangerous chemicals or weapons, more civilian lives become endangered. Canines serve as essential aids in the detection of explosives and the prevention of many deaths, but the need for more efficient and sensitive security measures in airports and on the battlefield is constantly growing.
Since the number of trained sniffer dogs in the world is limited, the development of electrical and mechanical detection devices is important for ensuring the safety and security of people around the globe. Currently, several different technologies exist that have the potential to detect explosives, especially for military and security purposes. Although some of these devices clearly mimic the physiological processes of the canine nose, others rely more substantially on mechanical and electrical fundamentals for operation. Regardless, engineers that design explosive detection technologies are inspired by the canine’s impeccable sense of smell and ability to identify harmful substances. Another factor influencing the development of detection devices is the nature of the most common explosive compounds.

A Look at the Common Explosive TNT

TNT (2,4,6 trinitrotoluene) remains one of the most widely employed explosives around the globe. TNT is a crystalline compound and is considered safe and simple to manufacture and handle, but has an exceptionally high explosive power [5]. TNT has been a major component of homemade bombs and landmines since World War I and is present in most unrecovered landmines in existence today. Annually, approximately 15,000-20,000 people are killed by landmines, many of which were planted dozens of years ago. Afghanistan consistently reports the highest number of casualties, mostly children, from landmines each year. Although approximately 100,000 mines are excavated around the world annually, if mine recovery continues at this rate, removal of the remaining mines will take hundreds of years – and that is if no more mines are implanted in the meantime [6]. Since most of the countries burdened with vast mine fields cannot afford adequate and effective detection devices, simple metal detectors serve as the most common method for mine investigation. Trained canines are still one of the best mine detectors around, but the availability of the best trained dogs is low, and transporting explosive-sniffing dog teams from one country to another is very expensive. Furthermore, just as humans sometimes die in the process of searching for mines, dogs may lose their lives as well. Consequently, there exists a tremendous need for inexpensive and accurate mechanical or electrical devices that can detect TNT in order to uncover landmines and homemade bombs [5].