BS 476-13 is the 13th part of the multiple series that specifies a method for examining the ignition characteristics of the exposed surfaces of specimens of essentially flat materials, composites, or assemblies not exceeding 70 mm in thickness when placed horizontally and subjected to specified levels of thermal irradiance.
BS 476-13 on ignitability of products subjected to thermal irradiance is useful for:
Irradiance (at a point of a surface) is the quotient of the radiant flux incident on an infinitesimal element of the surface containing the point, by the area of that element
BS 476-13 specifies only a simple representation of a particular aspect of the potential fire situation typified by a radiant heat source and a flame. This will help you to ensure the existence of a certain quality of performance (in this case ignitability) considered to have a bearing on fire performance generally.
Overall, BS 476-13 provides you with test and test results with background information for the ignitability of products subjected to thermal irradiance.
ISO 5657:1986