PNNL

Abstract

In security applications, noncontact sampling provides a less invasive means of explosives screening than physical swiping. Vapor collection and detection are inherently noncontact and ideal for standoff detection of explosives. However, explosive vapor detection is a challenge due to the low levels of vapors available for detection, partly driven by the low vapor pressure of target compounds (parts per trillion [pptv] to sub-parts per quadrillion [ppqv]). Atmospheric flow tube-mass spectrometry (AFT-MS) has demonstrated noncontact explosives vapor detection at pptv to ppqv levels. This study demonstrates that the ppqv sensitivity of AFT-MS with a high-volume air sampler enables standoff detection of trace explosives vapor at distances of centimeters to meters. Standoff detection of explosives vapor was possible both upstream and downstream of the vapor source relative to room air currents. RDX vapor from a saturated source was detected at up to 2.5 m, and RDX residue and nitroglycerin residue levels were detected at distances up to 0.5 m. The sampling can be optimized by accounting for air movement in the room or environment, which could further extend standoff detection distances. Using AFT-MS with a high-volume sampler would also be effective for standoff vapor detection of drugs and additional chemical threats and could be useful for security screening applications such as at mail facilities, border crossings, and security checkpoints.