37 Servicing, repair and installation of-- apparatus and instruments for detecting articles, particles and substances, namely, biological agent detectors, chemical agent detectors, explosives detectors, particle detectors and narcotics detectors, security and inspection apparatus and instruments, namely metal detectors, x-ray apparatus and instruments, namely, baggage, package, freight and cargo x-ray imagers, apparatus and instruments for scanning people, baggage, packages, containers, vehicles, namely, scanners, x-ray scanning and imaging apparatus and instruments, namely, x-ray scanners and imagers, chemical and biological detector apparatus and instruments, namely, chemical and biological detectors, apparatus and instruments for detecting explosives, drugs, and contraband namely, explosive detectors, drug detectors, and contraband detectors, trace substance detectors, spectrometer apparatus and instruments, namely, spectrometers, infra-red spectrometers and ion mobility spectrometers, meteorological apparatus and instruments, namely, radiosondes and meteorological stations