A puzzling results were reported for burn time of Al nanoparticles at T = 1100 degrees C. At a heating rate of 10(3) C/s, the burn time exceeds 1 s [K. Park, D. Lee, A. Rai, D. Mukherjee, M. Zachariah, J. Phys. Chem. B 109 (2005) 7290-7299; M. Zachariah, private communication], while after fast heating (107 C/s), the burn time was only 500 us [T. Bazyn, H. Krier, N. Glumac, Combust. Flame 145 (4) (2006) 703-713; T. Bazyn, H. Krier, N. Glumac, Proc. Combust. Inst. 31 (2007) 2021-2028]. This result is explained by the melt dispersion oxidation mechanism that operates for rapid heating only. Some characteristic parameters of this mechanism (critical heating rate, characteristic cluster size) are estimated. (C) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved.