Material burning performance classification testing evaluates how construction products, polymers, textiles, and other materials ignite, spread flame, release heat, and produce smoke under standardized fire conditions. Based on frameworks such as GB 8624-2012, EN 13501-1, UL 94, and ASTM E84, this testing assigns fire performance grades that determine whether products can legally enter building, transportation, and electrical markets. Accredited third-party laboratories conduct these tests to support regulatory compliance, product certification, and fire safety engineering.
Technical Overview
Burning performance classification testing is a systematic evaluation of how a material behaves when exposed to an ignition source, a developing fire, or fully developed fire conditions. The results are expressed as a classification grade rather than a simple pass or fail, allowing regulators, designers, and purchasers to compare the fire hazard of different products on a common scale. Classification schemes are embedded in mandatory building codes, product safety directives, and industry specifications worldwide.
Several major classification systems dominate global practice:
- GB 8624-2012 – The Chinese national standard for the burning behavior classification of building materials and products, harmonized in structure with the European system. It assigns grades A, B1, B2, and B3, with sub-grades A1, A2, B, C, D, and E, plus F for unclassified materials.
- EN 13501-1 – The European fire classification of construction products, using Euroclasses A1, A2, B, C, D, E, and F, supplemented by additional classifications for smoke production (s1, s2, s3) and flaming droplets or particles (d0, d1, d2).
- UL 94 – The recognized standard for the flammability of plastic materials for parts in devices and appliances, with grades such as V-0, V-1, V-2, 5VA, 5VB, and HB.
- ASTM E84 – The North American Steiner tunnel test measuring surface burning characteristics of building materials, producing Class A, B, or C ratings based on flame spread index and smoke developed index.
A complete classification typically combines data from multiple test methods. For example, a B1 (class B) certification under GB 8624-2012 requires passing the single-flame ignitability test together with the single burning item (SBI) test, and the reported grade carries suffixes describing smoke and dripping behavior. Understanding which combination of tests applies to a given product is therefore essential for an efficient certification program.
Testing Samples
Building and Decoration Materials
Interior and exterior construction products form the largest category of classified materials. Typical samples include wall and ceiling linings, partitions, gypsum boards, wooden panels, aluminum-plastic composite panels, insulation materials, roofing products, flooring, and fireproof coatings. These products are evaluated against GB 8624-2012 or EN 13501-1, with the required grade depending on the installation location and the fire compartment requirements of the applicable building code.
Plastic and Polymer Materials
Engineering plastics, thermoplastics, thermosets, compounds, and finished plastic components used in electrical and electronic equipment are assessed under UL 94 using standard bar and plaque specimens. Test results are widely referenced in product safety standards for appliances, IT equipment, and luminaires, where enclosure and support materials must meet minimum flame ratings.
Textiles and Flexible Materials
Curtains, drapes, blinds, awnings, seat coverings, wall fabrics, and nonwoven materials are tested for ignitability, flame spread, and damage length. Depending on the application, requirements may come from GB/T 5455 vertical flame testing, NFPA 701, or the textile-specific clauses of GB 8624-2012.
Wire and Cable Materials
Cable jackets, insulation compounds, and finished cables are classified for flame propagation, smoke density, and halogen content. Relevant frameworks include the cable burning behavior grades in GB 8624-2012, EN 50399 and EN 60332 series tests, and flame retardancy evaluations under IEC standards.
Foam and Functional Materials
Rigid polyurethane foam, polystyrene foam, phenolic foam, rubber foam insulation, acoustic panels, and adhesive products are frequently tested because of their high fuel load. Depending on density and intended use, these materials may be evaluated for combustion heat value, flame spread, and dripping behavior.
Testing Items
A classification program is built from discrete, quantifiable fire performance parameters. The principal testing items include:
- Ignitability – Whether and how quickly the specimen ignites under a small flame source, measured as flame application time, afterflame time, afterglow time, and flame tip reach (EN ISO 11925-2, GB/T 8626).
- Lateral flame spread – The extent of flame propagation upward and sideways on a vertically mounted specimen.
- Heat release rate – Total heat release (THR) and fire growth rate index (FIGRA) measured in the single burning item test, which together characterize the contribution of the product to fire development.
- Smoke production – Total smoke production (TSP), smoke growth rate index (SMOGRA), and smoke density ratings, which reflect the obscuration hazard during a fire.
- Flaming droplets and particles – Whether burning debris falls and whether it ignites filter paper below the specimen, reported as d0, d1, or d2.
- Gross heat of combustion – The potential heat energy of the material determined by oxygen bomb calorimetry (EN ISO 1716, GB/T 14402), used to distinguish non-combustible and limited-combustible products.
- Non-combustibility – Mass loss, sustained flaming, and furnace temperature rise of specimens held at 750 °C in a furnace (EN ISO 1182, GB/T 5464).
- Vertical and horizontal burning characteristics – Afterflame and afterglow times, ignition of cotton indicator, and burn rates for plastic specimens under UL 94 and IEC 60695-11-10/-20.
- Limited oxygen index (LOI) – The minimum oxygen concentration required to support candle-like combustion (ISO 4589-2, GB/T 2406.2), widely used for material development and quality control.
- Surface burning characteristics – Flame spread index and smoke developed index obtained from the tunnel furnace method (ASTM E84, GB/T 8627).
Testing Methods
Each classification grade corresponds to a defined combination of test methods. The core techniques used by accredited third-party laboratories are described below.
Single Flame Source Test (EN ISO 11925-2 / GB/T 8626)
A small propane flame is applied to a vertically oriented specimen, either at the bottom edge or to the surface, for 15 or 30 seconds. Ignition, flame spread beyond a defined height within a specified time, and burning droplets are recorded. Passing this test is a prerequisite for classes B through E under both GB 8624-2012 and EN 13501-1.
Single Burning Item Test (EN 13823 / GB/T 20284)
The SBI test simulates a burning waste basket placed in the corner of a room. Two specimens forming an L-shaped assembly are exposed to a 30 kW burner, and heat release and smoke production are measured continuously. Key outputs are FIGRA0.2MJ, FIGRA0.4MJ, THR600s, SMOGRA, and LFS (lateral flame spread), which determine classes B1 (B/C) and B2 (D/E) and the smoke and droplet suffixes.
Non-Combustibility Furnace Test (EN ISO 1182 / GB/T 5464)
Cylindrical specimens are stabilized and then inserted into a furnace at 750 °C for 30 minutes. Mass loss, duration of sustained flaming, and furnace thermocouple temperature rise are measured. Materials meeting the strict criteria are candidates for classes A1 and A2.
Bomb Calorimeter Test (EN ISO 1716 / GB/T 14402)
The specimen, in powdered or fragmented form, is completely burned in a high-pressure oxygen atmosphere inside a calorimeter. The gross heat of combustion (PCS) is determined, which allows classification of materials with very low potential heat release, such as mineral wool or inorganic boards, into the highest grades.
Vertical and Horizontal Burning Tests (UL 94 / IEC 60695-11-10)
Standard bar specimens are subjected to defined flame applications in a vertical or horizontal orientation. Afterflame time, afterglow time, cotton ignition, and flaming spread to the holding clamp determine the V-0, V-1, V-2, 5VA, 5VB, or HB rating. These ratings are the primary flammability acceptance criteria for plastic parts in electrical products.
Tunnel Furnace Test (ASTM E84)
A specimen measuring approximately 7.3 m long is mounted as the ceiling of a horizontal tunnel and exposed to an air-ventilated gas flame. Flame spread distance over time and smoke transmission are compared with reference materials to calculate the flame spread index and smoke developed index, yielding Class A, B, or C.
Cone Calorimeter Test (ISO 5660-1)
A 100 mm × 100 mm specimen is exposed to a controlled radiant flux, typically 25 to 75 kW/m². Time to ignition, peak and total heat release rates, smoke production, and mass loss are measured. While primarily a research and performance-based engineering tool, cone calorimeter data also supports product development and certain hazard assessments.
Oxygen Index Test (ISO 4589-2 / GB/T 2406.2)
The specimen is burned in a vertically mounted chimney with a flowing mixture of oxygen and nitrogen. The minimum oxygen concentration that just supports combustion for a specified time or length is reported as the LOI value. Higher LOI values indicate greater intrinsic flame resistance.
Smoke Density and Supplementary Tests
Smoke density chambers (ISO 5659-2), toxicity assessments, and glowing combustion tests supplement classification programs for transportation interiors, cables, and other high-hazard applications. For railway applications, EN 45545-2 combines multiple parameters into hazard level requirements HL1, HL2, and HL3.
Applications
Classification test reports are gateways to market access and legal installation across many industries:
- Building code compliance – Chinese building codes mandate minimum GB 8624-2012 grades for wall linings, ceiling finishes, insulation, and decoration materials in different building categories, with stricter requirements for crowded venues, high-rise buildings, hospitals, and schools.
- CE marking and European markets – EN 13501-1 classifications support the declaration of performance required for construction products placed on the European market under the Construction Products Regulation.
- Electrical and electronic products – UL 94 ratings are referenced in end-product safety standards for appliances, power supplies, connectors, enclosures, and printed circuit boards.
- Transportation – Rail vehicles, buses, ships, and aircraft require classified materials for seat assemblies, panels, flooring, and cable systems under frameworks such as EN 45545-2 and applicable regulations.
- Tendering and procurement – Government projects, subway systems, airports, and large commercial developments routinely specify A or B1 grades as prequalification conditions for suppliers.
- Product development and quality control – LOI, UL 94 screening, and cone calorimeter data guide formulation of flame-retardant compounds and monitor production consistency.
FAQ
Q: What is the difference between grade A and grade B1 under GB 8624-2012?
Grade A (A1/A2) designates non-combustible or practically non-combustible materials verified by the furnace and calorimeter tests, with very low heat of combustion and negligible flame involvement. Grade B1 (B/C) designates flame-retardant materials that resist ignition from a small flame and strictly limit heat release and flame spread in the SBI test, but which are still combustible in nature.
Q: What sample sizes and quantities are required?
Requirements depend on the test method. Typical SBI specimens are 1500 mm × 500 mm and 1500 mm × 1000 mm panels with several replicates; single flame tests use 250 mm × 90 mm specimens; UL 94 bars are 125 mm × 13 mm; non-combustibility specimens are 45 mm diameter × 50 mm cylinders; calorimeter tests require powdered material. Laboratories should be consulted early so that specimens are cut and conditioned correctly.
Q: How do GB 8624-2012 and EN 13501-1 compare?
The two systems share the same test methods and a similar class ladder, and GB 8624-2012 was technically aligned with EN 13501-1. However, they remain separate legal frameworks: a GB 8624 report is required for the Chinese market, while an EN 13501-1 classification with notified body involvement is required for CE marking. Parallel testing programs are often run from the same production batch to satisfy both markets.
Q: What do the suffixes such as B1 (B-s1, d0) mean?
The suffixes quantify additional hazards. The smoke classification s1, s2, or s3 describes total smoke production and smoke growth rate, with s1 the best. The droplet classification d0, d1, or d2 describes flaming droplets and particles, with d0 meaning none. High-occupancy venues typically demand the best suffix combinations, for example B-s1, d0.
Q: How long does classification testing take?
Simple screening tests such as UL 94 or oxygen index can be completed within one to two weeks. Full GB 8624 or EN 13501-1 classification programs, which require multiple methods, specimen conditioning, and several replicates, generally take three to six weeks, excluding any re-testing triggered by borderline results. Early consultation with an accredited third-party laboratory on test matrix design helps avoid delays.
Q: Can one test report cover an entire product range?
Classification reports apply to the specific material, thickness, density, color, and mounting configuration tested. Variations in thickness, substrate, or formulation may require additional testing, although defined families and worst-case grouping rules can extend coverage across similar variants. Laboratories can advise on the most efficient grouping strategy for a product family.