Smelling Threats from a Distance Using people's unique scents to identify them before they get too close to troops could save soldiers' lives. The Army Wants Olfactory Sensors That Can Smell Potential Perps At A Distance -- Popular Science
If something doesn’t smell right, the Army wants to know about it. But while the Pentagon has been angling for a biosensors that can smell fear or nervousness in a person’s bodily emanations for some years now, the Army wants something more: The ability to “uniquely identify an individual based on scent” from a distance or even days after the person has left the scene.
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Update: Army Wants Sensors to Nab Sweaty, Smelly Security Threats -- The Danger Room
My Comment: I guess this is an extension from .... you can run but you cannot hide .... to .... you can run but we can smell you.