BS 476-12 Fire tests on building materials and structures — Part 12: Method of test for ignitability of products by direct flame impingement

1 Scope
This Part of BS 476 describes a method of test for the determination of the ignitability of materials, composites and assemblies subjected to direct
impingement of flames of different size and intensity but without impressed irradiance.

NOTE The titles of the publications referred to in this standard are listed on the inside back cover.

2 Definitions

For the purposes of this Part of BS 476, the following definitions apply.

2.1
sustained ignition

after withdrawal of the ignition source, the presence of a flame on the surface of the specimen that persists for at least 10 s

2.2
transient ignition

after withdrawal of the ignition source, the appearance of flashes, or flames, which are not sustained for a continuous 10 s

2.3
progressive smouldering

an exothermic oxidation not accompanied by flaming which is self-propagating, i.e. independent of the ignition source, and may be accompanied by
incandescence

2.4
flaming debris

matter flowing or separating from the specimen during the test procedure and falling below the initial lower edge of the specimen and continuing to
flame as it falls

2.5
afterflame
persistence of flaming of a specimen, under specified test conditions, after the ignition source has been removed

2.6
afterglow
persistence of glowing of a specimen, under specified test conditions, after cessation of flaming or, if no flaming occurs, after removal of the ignition source

2.7
flame application time
the time (in seconds) for which the burner is in its final testing position

2.8
constant mass
the state of a test specimen when two successive weighing operations, carried out at an interval of 24 h, do not differ by more than 0.1 % of the mass of the specimen or 0.1 g, whichever is the greater