1.1 This part of ISO 5658 specifies an intermediate-scale method of test for measuring the vertical spread (upward and downward) of flame over a specimen of a product orientated in the vertical position. A measure of lateral spread can also be obtained. It provides data suitable for comparing the performance of materials, composites or assemblies, which are used as the exposed surfaces of walls or other vertically orientated products in construction applications. Some products with profiled surfaces can also be tested with a modified procedure representative of the end-use conditions of the product. 1.2 Upward flame spread is not limited to surfaces which are vertical. It is recognized that an enhanced form of upward, wind-aided flame spread can also occur on surfaces at an angle greater than 20° from the horizontal without any external ventilation. This type of flame spread can occur in both planar sloping surfaces and stepped surfaces such as stairs. Flame spread in these situations can become very rapid and can cause serious problems in escape ways such as staircases. When assessing stepped or sloping surface materials, it may be more appropriate to use a vertical flame spread test rather than a test in which the specimen is horizontal. 1.3 This part of ISO 5658 is applicable to the measurement and description of the properties of materials, products, composites or assemblies in response to radiative heat in the presence of non-impinging pilot flames under controlled laboratory conditions. The heat source may be considered to represent a single burning item such as a wastepaper bin or an upholstered chair within an enclosure, and this scenario would generally be considered to apply during the early developing stage of a fire (see ISO/TR 11696-1 and ISO/TR 11696-2). This part of ISO 5658 should not be used alone to describe or appraise the fire hazard or fire risk of materials, products, composites or assemblies under actual fire conditions.