Earthquakes are lethal natural disasters frequently burying people alive under collapsed buildings. Tracking entrapped humans from their unique volatile chemical signature with hand-held devices would accelerate urban search and rescue (USaR) efforts. Here, a compact and orthogonal sensor array has been designed to detect the breath- and skin-emitted metabolic tracers acetone, ammonia, isoprene, CO2 and RH, all together serving as sign of life. It consists of three nanostructured metaloxide

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... ors (Si-doped WO3, Si-doped MoO3 and Ti-doped ZnO), each specifically tailored at the nanoscale for highly sensitive and selective tracer detection along with commercial CO2 and humidity sensors. When tested on humans enclosed in plethysmography chambers to simulate entrapment, this sensor array rapidly detects tracers of human presence with low parts-per-billion (ppb) level accuracy and precision, unprecedented by portable detectors but required for USaR. These results were validated by bench-top selective reagent ionization time-of-flight mass spectrometry (SRI-TOFMS). As a result, an inexpensive sensor array is presented that can be integrated readily into handheld or even drone-carried detectors for first responders to rapidly screen affected terrain.