A zirconia-based mixed potential sensor utilizing dense lanthanum chromite and Pt electrodes and porous yttria-stabilized zirconia (YSZ) electrolyte was used in an alternating HC mode (unbiased) and total NOx mode (50 nA bias current) to detect the HC and NOx deflagration remnants of a nitroglycerin/nitrocellulose propellant (Bullseye), ammonium nitrate and fuel oil, blackpowder, and urea (a high nitrogen content fertilizer). Unique HC and NOx sensor responses taken together with sufficient sensitivity to detect microgram quantities of Bullseye, directly and via capture of trace residue by swiping contaminated surfaces, suggest that detection and discrimination of high explosives using mixed-potential sensors is possible. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2988252] All rights reserved.