The determination of a suitable sensor location on quadrotor drones is a very important issue for chemical reconnaissance platforms because the magnitude and direction of air velocity is different for each location. In this study, we investigated a customized chemical reconnaissance system consisting of a quadrotor drone and a chip-sized chemical sensor for detecting dimethyl-methylphosphonate (DMMP; a Sarin simulant) and investigated the chemical detection properties with respect to the sensor position through indoor experiments and particle image velocimetry (PIV) analysis of the system. The PIV results revealed an area free of vortex–vortex interaction between the drone rotors, where there was distinctly stable and uniform chemical detection of DMMP. The proposed chemical reconnaissance system was found to be realistic for practical application.

Early alerts for avoiding exposure to toxic chemical threats are critical applications of sensors to protect both military troops and civilian populations. Among the various sensing techniques developed, the passive Fourier transform-infrared (FT-IR) spectroscopy method has been demonstrated to work well as a remote (kilometer-scale) sensor for such early-alert systems. The passive type FT-IR detector is capable of mobile detection of toxic gas clouds because of its small-scale interferometer and optical instruments. In this article, real-time FT-IR measurements of ammonia (NH₃) in 76 mm artillery smoke are reported using a commercial remote sensor and scored by a real-time analysis conducted using a custom algorithm based on the generalized likelihood ratio test (GLRT). Using these methods, we measured the real-time change in the ammonia spectrum and GLRT scores against concrete and forest backgrounds following artillery propellant detonation. We confirmed that the GLRT score characteristics depend on the background and found that the effect of rapid heat transfer from the propellant detonation to the ammonia was detected in the accumulated ammonia FT-IR spectra.

Unmanned aerial vehicles (UAVs) have been used as a new chemical reconnaissance platform in chemical, biological, radiological, and nuclear detection and in industrial monitoring and environmental research, owing to their mobility, unconventional accessibility, and safety. Based on the UAV’s payload and operational time considerations, the ultralight chip-sized chemical sensor is the most promising candidate for chemical reconnaissance among various chemical sensors. To optimize the UAV’s chip-sensor performance, realistic outdoor tests of chemical sensors during UAV flights have to be conducted to verify their performances. In this study, indoor and outdoor experiments were conducted with a carbon nanotube (CNT)-based chip sensor installed on the UAV to detect dimethyl methylphosphonates (DMMPs), commonly used as chemical warfare agent simulants. Based on the indoor tests, DMMP concentrations and the position/direction of the CNT sensor were analyzed to optimize the sensing performances during UAV operations. Based on outdoor tests, we confirmed that the chemical sensor mounted on the UAV could detect DMMP gases by moving designated pathways in realistic conditions.

Developing an accurate chemical warfare agent (CWA) vapor generator is critical for homeland security because it enables real-time monitoring of target agent concentration for testing and evaluation. We designed and built an elaborate CWA vapor generator that offers reliable long-term stability and real-time monitoring capabilities by coupling it with Fourier transform infrared (FT-IR) spectroscopy. We evaluated the reliability and stability of the vapor generator using a gas chromatography–flame ion detector (GC-FID) and conducted a comparison between the experimental and theoretical results of sulfur mustard (HD, bis-2-chloroethylsulfide), a real CWA, at concentrations ranging from 1 to 5 ppm. Our FT-IR-coupled vapor generation system showed real-time monitoring ability, which enables rapid and accurate evaluation of chemical detectors. The vapor generation system was able to generate CWA vapor continuously for over 8 h, demonstrating its long-term vapor generation capability. In addition, we vaporized another representative CWA, viz., GB (Sarin, propan-2-yl ethylphosphonofluoridate), and conducted real-time monitoring of GB vapor concentration with high accuracy. This versatile vapor generator approach can enable the rapid and accurate evaluation of CWAs for homeland security against chemical threats and can be used in constructing a versatile real-time monitoring vapor generation system for CWAs.

A critical limitation in developing portable Fourier transform-infrared (FTIR) stand-off chemical detectors is the detection library optimization, which reduces the number of false alarms and maintains the detection performance. Ideally, a detection library should be established through high-resolution (0.5 cm^-1) FTIR spectroscopy in the laboratory. However, owing to the weight requirement of a portable FTIR stand-off detector, its optical system and mirror-moving range have limitations. Consequently, most portable FTIR stand-off detectors have been developed with a low resolution of approximately 4–16 cm^-1. In this study, we developed a portable FTIR stand-off detector with a dual library of SF₆. Moreover, we investigated its detection efficiency effect depending on the single library condition through realistic long-range (3 km) SF₆ spectrum data in a field test.