Because explosives of any type often release their own vapor particles via leaks in the sealment of the explosives, a special type of bomb-detecting sensor, called an Ion Mobility Spectrometer or more informally "Sensor A," was developed to "sniff out" leaked particle clusters of C4 and other explosives via a method based on ion mobility spectrometry technology. Because of this, their detection is often marked as a cloud on radar to depict the general area of the explosives.