Here is a photo of the Vapor Tracer, a device being used in the drug wars to sniff out narcotics. Its nose is a mass spectrometry sensor, capable of finding tiny amounts of drugs by detecting the "mass-to-charge ratio of ions".

Built for demanding security environments where speed and accuracy are essential, the incredibly lightweight VaporTracer2 employs a unique trace particle detection system offering unparalleled security. The best of both worlds, it can either "sniff" particles and vapors or analyze microscopic particles caught in "sample traps" swiped across a surface. Always pushing the envelope, GE Ion Track is the only manufacturer to offer outstanding sensitivity in both sample techniques. Equipped with an advanced desorption unit that dramatically raises particle sampling performance.