Several experiments were conducted to improve understanding of the properties of airborne particles generated by detonation of conventional charges and explosives prepared from nanophase aluminum-powder materials. We, believe this is the first time that the time-dependent behavior of ultrafine particles produced by explosions are reported. Based on our analysis of the measurement data, it appears that the initial peak diameter of particles produced by the detonation of test charges in the experiments, irrespective of the original formulations. is in the proximity of 40 nm. The particles eventually grew to the size range between 100 and 300 nm within 30 min. Charges prepared from the nanophase powders (50- and 100-nm) produced significantly higher number concentration values than those from conventional formulation and 15-mum powder material. The differences were two orders of magnitude higher by 50-nm powder, one order by the 100-nm, and 2 times higher by the 15-mum powder charge in comparison to the conventional formulation. The reduction of total number concentration of particles over time produced by detonation of the four charges appears to follow a pseudo-first-order chemical kinetics-linear functional on a semi-log plot. Employing this functional, the particle removal rates estimated for the four charges ranged from 0.014 to 0.026 min(-1). The removal rates were found to be statistically different (at the 95% confidence interval). and in the following order: the rate for charge A < B < C < D. (C) 2004 Elsevier Ltd. All rights reserved.