Safety assessments need to look at the possibility of a fire in dust layers which could then propagate or initiate an explosion. The so-called burning class of a dust gives an indication of dust layer combustion behaviour. The burning class can be determined by a simple screening test. It is aimed to develop a European standard describing the methodology for the determination and classification of dust layer combustion behaviour.The standard should describe whether a fire started in a dust layer using an external ignition source can propagate, and if so to what extent . Based on the test result the combustion behaviour is classified according to the following:Type of Reaction Class No ignition 1 Brief ignition, rapid extinction 2 Localised combustion, negligible spreading 3 Smouldering or slow combustion without flame 4 Slow, quiet burning with flames 5 Very rapid combustion with flame propagation or rapid decomposition without flame 6 The standard will cover: - Details of the test set-up; - Description of test performance; - Classification procedure; - Effect of process conditions (e. g. process temperature).