Surveys show that burning nests of dusts have been ignition source for dust clouds involved in industrial explosions. The literature indicates, however, that hot nests are a poor ignition source and are difficult to convey through powder handling plant. This paper describes some test in which clouds of dusts with a range of Minimum Ignition Temperatures (MITs) were dispersed around dust agglomerations smouldering and flaming at various temperatures. Smouldering nests of dusts prove to be poor ignition sources for most dust clouds, failing to ignite dusts even when there is a large difference between the nest temperature and the MIT of the dust cloud. Smouldering nests with temperatures above approximately 700-800 degreesC were, however, able to ignite sulphur clouds. Flaming nests, on the other hand, were able to ignite clouds of dusts up to the maximum MIT used, 600-675 degreesC. Crown copyright (C) 2003 Published by Elsevier Science Ltd. All rights reserved.