What Should You Do About False Alerts? Mass Spectometry Would Help

Do you ever wish you had a machine to tell you what scents your dog false alerted on? It would be nice to get a definitive answer, especially when you don’t understand what happened after a seemingly easy search went haywire. While expensive, technology exists that can analyze the molecular composition of scents, and has been applied to study k9 scent detection. The results are informative.

According to the American Chemical Society1, mass spectometry machines have shown on some occasions that the dogs were not cheating, but in reality had detected unintentional contamination of narcotics samples. (Mass spectometers turn the atoms in a sample into charged particles (ions). Then they use electric and magnetic fields to sort, measure the weight, and report the “relative abundance” of each ion2). In a study by Ong et al, mass spectometers were used for a real-time analysis of vapor samples that had caused alleged “false alerts” by trained bomb dogs. The results proved that the samples humans intended as “blanks” were unintentionally cross-contaminated with interfering scents. That’s helpful information: the detection dogs had alerted correctly, and the humans were decisively wrong.

Could this happen to you? Since humans can’t smell or see most odors we ask our dogs to search for, we all inevitably make some mistakes, causing a confusing conundrum for our detection dogs, without realizing a problem exists. Thank goodness a variable reinforcement schedule strengthens behaviors. Because sometimes even professional scent detection trainers withhold rewards when the dog’s performance was correct and the human misunderstood.

The next time your detection dog alerts in an area you think is free of target odor, consider the possibility that you might be the one who’s wrong. Yes, dogs make mistakes and more training may be warranted. But when you can’t use a mass spectometer (which is almost always), odor hygiene is the remaining tool you have to rely upon in determining what sniffer dogs are finding, whether in practice or in the field.  If there’s any doubt about the purity of your target odor, discard it and start with a fresh sample, prepared fastidiously, without admixing contaminants. Knowing that no human is perfect, the least you can do for your scent detection canine is to anticipate and minimize human error at every opportunity.


  1. Ta-Hsuan Ong, Ted Mendum, Geoff Geurtsen, Jude Kelley, Alla Ostrinskaya, Roderick Kunz. Use of Mass Spectrometric Vapor Analysis To Improve Canine Explosive Detection EfficiencyAnalytical Chemistry, 2017; 89 (12): 6482 DOI: 10.1021/acs.analchem.7b00451
  2. https://chem.libretexts.org/Core/Analytical_Chemistry/Instrumental_Analysis/Mass_Spectrometry/How_the_Mass_Spectrometer_Works

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