Conventional bomb detectors are designed to respond to only energetic materials e.g. nitrates, and not to detect other background chemicals in odors. Conversely, electronic noses are designed to respond to all chemicals within an odor. Based upon this distinction electronic noses might not be considered good bomb detectors where there are strong background odors. On the other hand, bomb detectors might not be very good electronic noses because they are blind to many important environmental and olfactory chemicals. However, the diversity of today’s terrorist threats (explosive, chemical, and biological) makes it increasingly apparent that there is a role for electronic noses with the ability to quickly learn and recognise threat vapors of any kind.