ISO 21367:2007 specifies a test method for plastics for the determination of the heat release rate, ignitability, surface spread of a flame, falling droplets/particles and smoke production using a "medium" scale specimen that simulates the early development stage of the fire. This test method can be used as a screening test for intermediate scale and large scale tests in addition to its use in factory production control, research and product development.

ISO 21367:2007 provides data that is suitable for comparing reaction-to-fire performance of many materials, products, composites or assemblies under end use application conditions.

The results of this test method are limited to specimens with heat release rates of less than 10 kW.