The Smell of Money


By Lisa Jancarik

An estimated $30 billion in illegal cash crosses U.S. borders into Mexico annually. Border Patrol has the daunting job of finding it before it leaves, and last year, U.S. officials seized $106 million. The Department of Homeland Security recently put out a public call for currency detection devices. KWJ Engineering responded with a money-sniffing instrument. The Bulk Currency Detection System (BCDS) relies upon gas chromatography/mass spectrometry (GC/MS).

GC/MS uses a small sample that is vaporized and transmitted via carrier gas through a tube coated with a solid chemical. The solid chemical is selected according to the sample to be separated. The sample chemical least likely to bind to the solid chemical elutes (i.e., comes out of the tube) first, the next least likely to bind second, and so on. The separated components tell the user what makes up the sample.

Gas chromatography is ideal for compounds like the ones American dollars emit. According to Dr. Joseph Stetter of KWJ Engineering, their device can identify the chemical fingerprint of money in less than a minute.

GC/MS Challenges to Using GC/MS

Stetter's firm had to figure out how to find the dollar's chemical signature. To identify the "smell" of money, they sealed 100 used $1 bills in a chamber and warmed them to release vapors. The chemicals that showed up in all the results make up the smell of money. As it happens, this chemical signature comes from several aldehydes, furans and organic acids in parts per million (for security reasons, no one is allowed to publish the exact mix).

The BCDS trial period won't begin for another two to three years. Then, officers will use the proposed design, a backpack with a wand to wave over clothing or into baggage or vehicles. Detection of a high intensity of the chemical signature would indicate the presence of cash and allow illegal dollars to be seized.


  • Usually, these efforts involve sniffer dogs, who require training and may get sick. Dogs also have a limited ability to communicate, even with their trained handlers
  • Border patrol agents need a device that works at least as well as a dog for it to become practical. It has to be portable and rugged enough for a range of environments. Plus, it has to allow for processing right at the border