This International Standard specifies a method suitable, in the context of production control or product development, for assessing the heat release rate of substantially flat products subjected to controlled levels of radiation heating using an external ignition device in a horizontal orientation. In this test, the heat release rate is determined using a thermopile and not via oxygen consumption, which is evaluated in more precise processes. This test also measures the time until ignition (continuous burning with flame) occurs. The mass loss of the test specimen can optionally be determined.