The Alex Directive specifically includes the explosion hazards arising from the presence of flammable dusts. The European standards body CENELEC proposed a research project to develop tests for assessing the ignition hazard due to electrical apparatus used in hazardous dusty environments. This paper describes the work done on developing a test for electrical spark ignitions of explosive dust atmospheres. A prototype apparatus incorporating the dust explosibility vertical tube and the STA break flash apparatus has been developed. Tests using three dusts showed sulphur dust had ignition characteristics close to those of gas Group B, while other dusts were much less easily ignitable than methane. Round robin tests using a duplicate apparatus and the proposed test method produced results very close to those obtained using the original apparatus. Crown copyright (C) 2003 Published by Elsevier Science Ltd. All rights reserved.