Thermal stability of aluminum, iron and copper nanopowders, produced by electrical explosion of wire during heating in the air, was investigated in the work. Thermal analysis method was used for control of thermal stability for nano-dispersed metals in heating in the air. It was shown, that after a long time of storage in air electrical explosion metal nanopowders have had extra active ones. Estimation of velocity of flame spreading in poured layer of the powders was carried out. Quality changes in investigated samples, happened for storage time, lead to increase of flame front length and its line velocity. The results of the researches could be used for diagnostics of fire danger of nano-dispersed metals, also for selection of working regimes and provision of fire explosion safety for technologies which produce and apply of nano-dispersed metal powders. Time-factor have not effected on criteria concerning the danger of the loads and have not changed its marking.