Defining Flash Compositions: Modifications to UN Time/Pressure Test

Abstract: The Time/Pressure Test from the UN Manual of Tests and Criteria has been modified to define flash compositions in the default classification lists for fireworks in the UN Model Regulations. This modified test is known as the HSL flash composition test. This paper summarises the history of this change from a composition-based to a performance-based definition and describes more recent work to improve the method when testing pyrotechnic compositions. A modified test method has been developed with a new firing plug that has been designed to improve reliability and reproducibility by changing the sample geometry and removing the primed cambric. The system has been manufactured and tested and was presented as a proposal to the UN Subcommittee of Experts on the Transport of Dangerous Goods as an additional test method for the Manual of Test and Criteria specifically for defining hazardous compositions with flash-like properties. The method and apparatus is now incorporated into the UN scheme for the classification of dangerous goods, specifically for fireworks.

Keywords: Flash Composition, UN Default List, Time/Pressure Test.