BS 476-13:1987 download.Fire tests on building materials and structures Part 13: Method of measuring the ignitability of products subjected to thermal irradiance —  [ISO title: Fire tests — Reaction to fire — Ignitability of building products].
o Introduction
0.1 Fire is a complex phenomenon: its behaviour and its effects depend upon a number of interrelated factors. The behaviour of materials and products depends upon the characteristics of the fire, the method of use of the materials and the environment in which they are exposed. The philosophy of “reaction to fire” tests is explained in ISO/TR 3814.
0.2 A test such as is specified in BS 476-13 deals only with a simple representation of a particular aspect of the potential fire situation typified by a radiant heat source and a flame; it cannot alone provide any direct guidance on behaviour or safety in fire. A test of this type may, however, be used for comparative purposes or to ensure the existence of a certain quality of performance (in this case ignitability) considered to have a bearing on fire performance generally. It would be wrong to attach any other meaning to performance in this test.
0.3 The term “ignitability” is defined in ISO 3261 as the capability of a material of being ignited. It is one of the first fire properties to be manifest and should almost always be taken into account in any assessment of fire hazard. It may not, however, be the main characteristic of the material which affects the subsequent development of fire in a building.
0.4 This test does not rely upon the use of asbestos-based materials.
0.5 The attention of all users of the test is drawn to the following warning.
SAFETY WARNING — So that suitable precautions may be taken to safeguard health, the attention of all concerned in fire tests is drawn to the possibility that toxic or harmful gases may be evolved during exposure of test specimens. The advice on safety given in Annex A. clause A.7 should also be noted.
1 Scope and field of application
BS 476-13 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.
2 References
ISO 291, Plastics — Standard atmospheres for conditioning and testing.
ISO 3261, Fire tests — Vocabulary. ISO/TR 3814, The development of tests for measuring “reaction to fire” of building materials.
6.1.6 Assemblies shall be tested as specified in 6.1.3 or 6.1.4 as appropriate. However, where thin materials or composites are used in the fabrication of an assembly, the presence of air or an air gap and/or the nature of any underlying construction may significantly affect the ignition characteristics of the exposed surface. The influence of the underlying layers should be understood and care taken to ensure that the test result obtained on any assembly is relevant to its use in practice (see A.4.1).
When the product is a material or composite which would normally be attached to a well-defined substrate, then it shall be tested in conjunction with that substrate using the recommended fixing technique, e.g. bonded with the appropriate adhesive or mechanically fixed.
6.2 Baseboards
6.2.1 One baseboard will be required for each test specimen. However, since it will sometimes be possible to re-use the baseboard after test, the total number required will depend on the frequency of testing and the type of product being tested.
6.2.2 The baseboards shall be square with sides measuring I 65_ mm and shall be made of non-combustible insulation board of oven-dry density 825 ± 125 kg/ms and nominal thickness 6 mm.
6.2.3 Before use in a test, a baseboard shall be placed for at least 24 h in an atmosphere at a temperature of 23 ± 2 °C and a relative humidity of (50 ± 5) %, with free access of air to both sides.
6.3 Conditioning of specimens
(See also sub-clause A.4.3 in Annex A.)
Before test the specimens shall be conditioned to
constant masse at a temperature of 23 ± 2°C, and a
relative humidity of (50 ± 5) %.
6.4 Preparation
6.4.1 A conditioned specimen shall be placed on a baseboard treated according to 6.2.3 and the combination shall he wrapped in one piece of aluminium foil of nominal thickness 0,02 mm from which a circle 140 mm diameter has been previously cut (see Figure 1). The circular cut-out zone shall be centrally positioned over the upper surface of the specimen. After preparation the specimen-baseboard combination shall be returned to the conditioning atmosphere until required for test.
For these measurements, the opening in the masking plate shall be completely filled; it is necessary to employ a number of calibration boards of special horizontal shapes and sizes.
7.3.3 The radiator cone shall be located and secured from the vertical guide rods of the specimen support framework by clamps which position the lower rim of the radiator cone shade 22± 1 mm above the upper surface of the masking plate.
7.3.4 Details of the radiator cone are shown in Figure 4b).
7.3.5 The temperature of the radiator cone shall be controlled by reference to the reading of a thermocouple (primary thermocouple) (9.1) in close and stable thermal contact with the heater element tube. A second thermocouple (secondary thermocouple) shall be attached similarly, mounted in a diametrically opposite position. The thermocouples shall have a speed of response not worse than that of a thermocouple with insulated hot junction in a stainless steel sheath 1 mm in diameter. Each thermocouple shall be attached to a coil of the heater element tube which places them between one-third and half way down from the top of the radiator cone. At least 8 mm of the end of the thermocouple shall lie in a region of approximately uniform temperature.
A description of methods of attaching thermocouples which have been found satisfactory in practice is given in Annex A (clause A.5.1).
7.4 Pilot flame application mechanism (See also clause A.5.2 in Annex A.)
7.4.1 The apparatus shall be provided with a mechanism which is capable of bringing a pilot flame from a re-ignition position outside the radiator cone to the test position within the cone. The mechanism shall be capable of taking the pilot flame through the radiator cone and through the aperture in the masking plate to a maximum distance of 60 mm below the underside of the masking plate.
7.4.2 The pilot flame shall issue from a nozzle made of stainless steel as specified in Figure 5, attached near the end of the pilot flame tube.
14 Test report
The test report shall be as comprehensive as possible and shall quote the individual specimen ignition times for each irradiance tested. Any observations made during the test and comments on any difficulties experienced during testing shall also be given. The following essential information shall also be given in the test report and shall additionally be included in a summary test report:
a) name and address of test laboratory; b) name and address of sponsor; c) name and address of manufacturer/supplier; d) full description of the product tested including trade name, together with its composition, construction, orientation, thickness, density and mass of the conditioned specimen before test and where appropriate the face subjected to test (note particularly 5.1.2). Details of substrates used and fixing methods shall be given. With composites and assemblies the thickness and density of each of the components shall be given, together with the apparent (i.e. overall) density of the whole;
e) for some products the date of manufacture and information about subsequent treatment andlor exposure may be of importance;
f) the statement: “The test results relate only to the behaviour of the test specimens of a product under the particular conditions of the test; they are not intended to be the sole criterion for assessing the potential fire hazard of the products in use”.
A suggested summary test report is given in Annex B.