Among the industrial sectors that are affected by dust explosions, the metal working industry is one of the most frequently involved. Metal dusts are often the by-products of mechanical workings. Dust producing machines are widely distributed, small in size and are generally located in workplaces. Abatement plants are also often located in the working area. The companies that are involved in these explosions are often small, and thus often have limited resources. These factors generally lead to difficulties in managing the risk of explosions. This paper has the aim of investigating the flammability of waste dust produced by metal workings, and to define the dust properties that are more likely to lead to an explosion. For this purpose, a simple and fast flammability test has been used as a cheap way of characterise the flammability of the samples. The test has been called the Speedy Esplosibility Test (SET), and it is similar to the procedure suggested in the new ISO/IEC standard (ISO/IEC 2016) that came into force recently. SET is composed of 4 different tests, derived from standard procedures, each of which represents a different ignition mechanism: High voltage continuous arc ignition and glowing wire ignition in a Hartman 1.21 tube (based on UNI EN 13821:2004); Dust cloud ignition in a G-G furnace and dust layer ignition on a hot plate (based on UNI EN 50281:1999). The SET results are compared with the standard flammability classification obtained according to ISO, 2016ISO/IEC 80079:2016, with the standard K-St measurement in the 20-L Siwek Sphere, and with tests in the 20-L sphere with 2 x 1 kJ igniters, respectively according to the UNI EN 14034: 2011 part 2 and part 3. Moreover, the morphology and chemical nature of the dusts have also been determined and their effects on dust explosibility are discussed. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.