GB 8624-2025Classification for burning behavior of building materials and products (English PDF)

3.1 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1.1 material - a single substance or a uniformly dispersed mixture of substances. Example: metal, stone, timber, concrete, polystyrene resin, polyurethane resin, glass wool, rock wool.

3.1.2 product - a material, element or assembly for which information is required. Example: wood-based panels, extruded polystyrene foam, polyurethane composite insulation board, rock wool board, nylon carpet, decorative and fitting-out products such as decorative fabrics, mattresses and hard furniture.

3.1.3 burning behavior - the reaction to fire of materials and products under specified conditions.

3.1.4 flat material and product - a material or product whose cross-section is approximately rectangular and whose width is much greater than its thickness. Note 1: its surface is usually flat, although some products have regular projections or recesses. Note 2: such products are usually used for walls, partitions and ceilings.

3.1.5 flooring material and product - a material or product laid on a floor. Example: carpets, plastic floors, timber floors, floor mats, floor coatings.

3.1.6 roof covering material and product - a material or product covering the surface of the roof substrate of a building.

3.1.7 thermal insulation material and product for building - an insulating material or product used for thermal insulation of the walls, roofs, floors, pipes and so on of buildings.

3.1.8 wall thermal insulation product - an insulation product used on the internal or external walls of buildings.

3.1.9 roof thermal insulation product - an insulation product used on building roofs.

3.1.10 floor thermal insulation product - an insulation product laid on floors inside buildings.

3.1.11 sandwich composite thermal insulation product - a composite insulation product for walls and roofs made by bonding non-combustible boards to both faces of an insulating material, excluding edge sealing materials. Example: metal-faced insulating sandwich panels for buildings, calcium silicate faced composite insulation boards.

3.1.12 pipe thermal insulation product - a functional product applied to the outer surface of a pipe by prefabrication or site installation to restrict heat conduction and reduce heat transfer from the medium. Note 1: it includes tubular products and flat pipe insulation products. Note 2: insulation with an outside diameter not greater than 300 mm is treated as a tubular product, and insulation with a larger outside diameter as a flat pipe insulation product.

3.1.13 photovoltaic module - a complete, environmentally protected assembly of interconnected photovoltaic cells able to deliver direct current on its own. Note: it generally consists of a laminate, a junction box and, where present, a frame.

3.1.14 homogeneous product - a product consisting of a single material, or having uniform density and composition.

3.1.15 non-homogeneous product - a product that does not meet the definition of a homogeneous product and consists of several substantial and/or non-substantial components.

3.1.16 substantial component - a material forming a significant part of a non-homogeneous product, having a mass per unit area of not less than 1.0 kg/m2 or a thickness of not less than 1.0 mm in a single layer. Note: two or more adjacent non-substantial layers with no substantial component between them are regarded as one substantial component if together they meet the requirements for one.

3.1.17 non-substantial component - a material not forming a significant part of a non-homogeneous product, having a mass per unit area of less than 1.0 kg/m2 and a thickness of less than 1.0 mm in a single layer. Notes: adjacent non-substantial layers with no substantial component between them that together do not meet the requirements for one non-substantial component are regarded as a substantial component; if together they do meet them, they are regarded as one non-substantial component.

3.1.18 internal non-substantial component - a non-substantial component covered on both faces by at least one substantial component.

3.1.19 external non-substantial component - a non-substantial component with one face not covered by a substantial component.

3.1.20 substrate - the material behind the product, in direct contact with it or with a suitable air gap. Example: concrete walls, timber, metal sheet.

3.1.21 standard substrate - a product that represents the substrate used in end-use applications.

3.1.22 gross heat of combustion (PCS) - the heat released by the complete combustion of unit mass of a material when all the water produced is condensed to liquid.

3.1.23 net heat of combustion (PCI) - the heat released by the complete combustion of unit mass of a material when all the water produced remains as vapour.

3.1.24 flaming droplets/particles - material separating from the specimen during a fire test and continuing to flame for at least the minimum time specified by the test method.

3.1.25 critical heat flux (CHF) - the lower of the heat flux at the point where the flame goes out and the heat flux after 30 min of test, that is, the heat flux corresponding to the furthest extent of flame spread within 30 min.

3.1.26 fire growth rate index (FIGRA) - the maximum value of the ratio of the heat release rate of the specimen to the time of exposure. Examples: FIGRA0.2MJ and FIGRA0.4MJ are the maximum of that ratio after the total heat released by the specimen has reached 0.2 MJ and 0.4 MJ respectively.

3.1.27 smoke growth rate index (SMOGRA) - the maximum value of the ratio of the smoke production rate of the specimen to the time of exposure.

3.1.28 smoke toxicity - the degree of injury or harm caused by toxic and harmful substances in smoke.

3.2 Symbols and abbreviations

For the purposes of this document, the following symbols and abbreviations apply: CHF, critical heat flux, kW/m2; d, grade for flaming droplets/particles; FIGRA, fire growth rate index, W/s; Fs, flame tip height, mm; LFS, lateral flame spread; OI, oxygen index, %; PCI, net heat of combustion, MJ/kg; PCS, gross heat of combustion, MJ/kg or MJ/m2; SDR, smoke density rating; SMOGRA, smoke growth rate index, m2/s2; s, grade for smoke production; t, grade for smoke toxicity; tf, duration of sustained flaming, s; THR600s, total heat released in the first 600 s of exposure, MJ; TSP600s, total smoke production in the first 600 s of exposure, m2; Delta T, temperature rise, degrees C; Delta m, mass loss, %.

4.1 Classification

4.1.1 Classification of building materials and products: flat materials and products; flooring materials and products; roof covering materials and products; and building thermal insulation materials and products, subdivided into wall, roof and floor thermal insulation products, sandwich composite thermal insulation products and pipe thermal insulation products. Flat materials and products used on floors or as roof coverings are placed in the flooring or roof covering category respectively, and flat, flooring and roof covering materials and products used for building insulation are placed in the building thermal insulation category.

4.1.2 Classification of decorative materials and products: curtain and drapery fabrics for decorative covering; foam plastics for display, furniture and decoration; soft and hard furniture and components.

4.1.3 Classification of non-metallic materials and products for equipment and components: conduits for wires and cables and plastic enclosures of devices; photovoltaic modules.

4.2 Burning behavior grades

The burning behavior grades of materials and products are given in Table 1: grade A, non-combustible material (product); grade B1, flame-retardant (difficult to burn) material (product); grade B2, combustible material (product); grade B3, flammable (easily ignited) material (product).

5.1 Building materials and products

5.1.1 General. According to the category and the corresponding test standards, the burning behavior grade obtained under 5.1.2 to 5.1.5, together with the smoke production grade, the flaming droplets/particles grade and the smoke toxicity grade obtained under 5.1.6, make up the burning behavior grade information of a building material or product.

5.1.2 Flat materials and products. The grades and grading criteria of flat materials and products such as wall decorative panels, suspended ceiling boards and wood-based panels shall comply with Table 2. Table 2 divides grade A into classes A1 and A2, grade B1 into classes B and C, grade B2 into classes D and E, and grade B3 into class F, the last applying to products that do not reach B2. For each class it states the test standards to be used - the non-combustibility test of GB/T 5464 and the heat of combustion test of GB/T 14402 for classes A1 and A2, the single burning item test of GB/T 20284 for classes A2 to D, and the ignitability test with edge flame application of GB/T 8626 for classes B to E - and the criteria to be met, expressed as limits on temperature rise, mass loss, flaming duration, gross and net heat of combustion, fire growth rate index, lateral flame spread, total heat release, flame tip height and ignition of the filter paper by flaming droplets. The footnotes to the table state whether each test applies to a homogeneous product, to the substantial components or the external or internal non-substantial components of a non-homogeneous product, or to the product as a whole, and give the conditions under which a product with a low heat of combustion may still reach A1 or A2.

5.1.3 Flooring materials and products. The grades and grading criteria of flooring materials and products such as carpets, plastic floors, timber floors, floor tiles, floor mats and floor finishes shall comply with Table 3, which is organised on the same pattern of classes, test standards and criteria.