The fireball from a vented dust explosion presents a danger to personnel who may be within the vicinity of the event. The risk of serious injury to people caught within the fireball is great, and anyone just outside the fireball may be at risk from thermal radiation. This report describes a project in which the effects of thermal radiation from vented dust explosions was studied. The aim was to establish the areas around a fireball in which people would be at risk from thermal radiation. Six dusts were tested in a large vented vessel and external fireballs were generated under a range of conditions. The fireball geometry and the heat flux from the fireball were studied. A range of material samples were exposed to the fireball. The safe areas around the fireballs were established for each of the six dusts. Generally, the larger vent areas resulted in the larger fireballs and high heat pulse values. However, the fireball was usually too brief to ignite fabric samples unless they were very close to the fireball. The work has shown that in most cases the safe area was relatively close to the surface of the largest fireball. Crown Copyright