Physical and chemical evidence remaining after the explosion of large improvised bombs. Part 2: Firings of calcium ammonium nitrate/sugar mixtures

Six test firings of large improvised explosive devices were carried out. Th e principal objectives of the firings were to measure the physical effects of the explosions upon representative objects placed nearby and to recover any chemical traces deposited on these objects. The results are intended fo r use as an aid in determining the approximate size and type of an explosiv e employed in terrorist attacks. Three 454 kg charges of a mixture of calci um ammonium nitrate (CAN) fertilizer and sugar, and three 2268 kg charges o f a similar mixture, all confined in cylindrical steel containers were fire d. Each charge was surrounded by 19 road signs mounted on posts and four ve hicles, to act as witness materials. The analysis of aqueous swab extracts taken from the witness materials after firing showed the recovery of nitrat e, ammonium and low levels of glucose. No sucrose was detected. Nitrate was usually recovered in greater quantities than ammonium and recovery general ly decreased with increasing distance from the charges in any given directi on. Quantities recovered from objects placed at the same distance in differ ent directions Varied considerably. Patterns of physical damage to the witn ess materials could be discerned according to their distance from the charg e and the size of the charge. The velocities of detonation and air blast ef fects were measured.