A new standard reference material for trace explosive compounds is available from NIST for calibration of trace-explosives detectors. The testing package, SRM 2906, contains calibration solutions of three explosive compounds: RDX (cyclotrimethylenetrinitramine), an ingredient in C-4; pentaerythritol tetranitrate, or PETN; and TNT. According to NIST, the new reference standard satisfies the need for independent test materials with low uncertainties at concentrations necessary for reliable calibration of trace-explosives devices, such as those used at airports to check suspicious packages. The solutions provided by SRM 2906 are at concentrations near, but slightly above, the detection limit of commercial swipe-type detectors, which are commonly based on ion-mobility spectrometry. NIST worked with ASTM International so its material complies with ASTM standards.