Flame surface spread test

A description is given of the initiatives carried out within the European Community for the harmonization of fire testing. The technical and economic reasons are explained for such initiatives, which are taken in order to remove barriers to trade from the European internal market. Of the various fire aspects, only fire reaction testing is taken into consideration here, because it appears as a major technical obstacle to the free circulation of construction materials. All possible approaches are considered for the attainment of such a harmonization and one, the so called interim solution, is fully described. The proposed interim solution, is based on the adoption of three fundamental test methods, i.e. the British "Surface Spread of Flame", the French "Epiradiateur" and the German "Brandschacht", and on the use of a rather complicated "transposition document", which should allow to derive most of the national classifications from the three test package. 

The number of small scale test methods, used for classification purposes, should be limited and based on ISO tests, presumably the Cone Calorimeter /10/ (see Fig. 8) and possibly the ISO Surface Spread of Flame test /11/. 

Surface spread of flame test. The 13 materials listed in Table I were tested in the IMO and ISO surface spread of flame tests. 

Table I. Results from the Surface Spread of Flame Test and the Cone Calorimeter... 

Figure 1. Surface spread of flame test for particle board.

The Lateral Ignition and Flame spread Test (LIFT) apparatus was developed primarily for lateral flame spread measurements. The apparatus, test procedures, and methods for data analysis are described in ASTM E 1321. A sample of 155 x 800 mm is exposed to the radiant heat of a gas-tired panel. The panel measures 280 x 483 mm. The heat flux is not uniform over the specimen, but varies along the long axis as a function of distance from the hot end as shown in Figure 14.6. The flux distribution is an invariant of distance when normalized to the heat flux at the 50 mm position. When methane or natural gas is burnt, the upper limit of the radiant heat flux is 60-65 kW/m2. The lower limit is approximately 10kW/m2 since the porous ceramic tile surface of the panel is only partly covered with flame at lower heat fluxes. 

In flame spread tests, the specimen is ignited at the hot end by a nonimpinging premixed acetylene-air pilot flame. Flame spread rate over the surface is then monitored as a function of distance x. Thus, one experiment yields information on flame spread rate over a whole range of heat flux levels (or surface temperatures). Information to this extent can be obtained in one run owing to the particular shape of the flux invariant, which is the result of the specific geometry and specimen-panel arrangement shown in Figure 14.7. 

As mentioned earlier, the fire hazard of interior finish materials is primarily due to the potential for rapid wind-aided flame spread over the surface. It is therefore not a surprise that reaction-to-fire requirements for interior finish materials in U.S. building codes are primarily based on performance in a wind-aided flame spread test. The apparatus of this test is often referred to as the Steiner tunnel. The Steiner tunnel test is described in ASTM E 84. Although the test does not measure any material properties that can be used in a model-based hazard assessment, a discussion of the test is included here due to its practical importance for the passive fire protection of buildings in the United States. 

BS 476 Part 7 1987 Fire tests on building materials and structures Method for classification of the surface spread of flame of products. 

Boron compounds can be added in combination with other chemicals such as nitrogen and phosphorus. A solution containing sodium tripolyphosphate, boric acid, and ammonia provides a ready-to-use treatment on cellulose products such as plywood, fiberboard, and cardboard (87). The resulting products passed the British Standard 476, Section 6 (Fire Propagation test) Class 0 and Class I requirements of the British Standard Section 7 (Surface Spread of Flame). 

ISO DIS 9239 [83] determines the surface spread of flame of textile floor coverings using a radiant heat test and is similar to the test defined in ASTM E648 [84]. 

Surface spread of flame on building materials is tested according to ISO DP 5658-1977. A specimen board measuring 800 mm x 155 mm with a maximum thickness of 40 mm is ignited by the simultaneous application of a radiating surface and an 80 mm long propane flame. The vertically positioned radiating surface. 

Fig. 3.98 Arrangement of the surface flame spread test after BS 476 Part 7 1971 1 heat radiator 2 rear plate 3 specimen 4 igniting flame 5 gas inlet... 

BS 476 Part 7 1971 gives the surface flame spread test of building materials and includes two techniques one for characterizing building materials with large-size specimens and the other for estimative tests or quality control using small specimens. 

In the Netherlands, the standard NEN 3883 (1975) prescribes a flame spread test which is very similar to that in BS 476 Part 7 1971 but the size of the specimen is 1000 x 300 mm with a maximum thickness of 100 mm surface temperature of the heat radiator is 900 °C the hotter end of the specimen is ignited by a 180-mm gas flame during the course of the test procedure (10 min). The materials are rated in terms of flame spread according to Table 3.25. 

Flame spread flammability evaluates how far away from the ignition source a flame travels across a liquid or solid surface. The test is carried out in accordance with ASTM E162 [12]. Only flexible cellular foams are tested using a variant of the method ASTM D3675 [13]. 

Few unsaturated polyester resin-based laminates can achieve better than the F2 level with most only able to reach F3. However, in recent years, developments in resin technology have resulted in Ml (the best surface spread of flame requirement in the French test, which is equivalent to BS476 Part Class 1), and FO classifications with some filled resins (Seott Bader Crystic 343A). The major limitation is a maximum fibre eontent, by weight, of just 20%, which limits applications to semi- or non-struetural components only. Henee, sueh materials can be used for many decorative internal eomponents and cladding panels supporting their own weight. 

Spread of flame/LIFT (IMO FTP Code, Part 5 and ISO 5658-2) [International Maritime Organisation, Fire Test Procedures, test for surface flammability, 1998 and Lateral surface spread of flame on building products with specimen in vertical configuration, 1995]... 

British Standards Institution, London BS 476 Fire tests on building materials and structures Parts 1 2 withdrawn Part 3 1975 External fire exposure roof test Part 4 1970 Non-combustibility test for materials Part 5 1968 Ignitability test for materials Part 6 1968 Fire propagation tests for materials Part 7 1971 Surface spread of flame... 

BS 476 1968 Part 7 - surface spread offlame. Specified in Building Regulations in UK, Netherlands, Denmark and France. A 900 mm long specimen is mounted in front of a radiant panel in such a way as to be subjected to a specific hat intensity gradient. Six specimens of each material are tested and, if five show no more than 165 mm spread of flame and the sixth no more than 190 mm, the material is classified as Class 1. There is also a small-scale test, with specimens 300 mm long. Similar large-scale tests are described in NEN 3883 and DS 1058 3. NF P 92-506 can be compared with the small-scale test. 

France NF P92-501 - radiation test for rigid materials. A 400 mmx400 mm specimen is mounted at an angle of 45° and parallel to an electrically heated radiation source. Two propane gas burners are positioned close to the upper and lower faces of the specimen, to ignite flammable gases evolved from it. The test is carried out for a total of 20 minutes and flame spread is recorded. Surface spread of flame is also measured in test method NF P92-504. 

Materials are tested by insurance bodies and fire research establishments. The purpose of the tests is to classify materials according to the tendency for flame to spread over their surfaces. As with all standardized test methods, care must be taken when applying test results to real applications. 

BS 476 Part 7 1987 details the method for classification of the surface spread of flame of products (and its predecessor BS 476 Part 7 1971). The test is a classification system based on the rate and extent of flame spread and classifies products 1,2, 3 or 4 with Class 1 being the highest classification. 

This test, also known as the radiant panel test, is one of the most widely used laboratory-scale flame-spread tests. Although not recommended for use as a basis of ratings for building code, the test does provide a basis for measuring and comparing the surface flammability of materials when exposed to a prescribed level of radiant heat energy. 

The surface burning characteristics (flame spread index and smoke developed index) for wood and wood products as measured by American Society for Testing and Materials (44) can be reduced with fire retardant treatments, either chemical impregnation or coatings (48). Fire retardant treatments also reduce the heat release rate of a burning piece of wood (49,50). The heat release rates (51) of the burning materials are an important factor in fire growth. 

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