Combustion performance analysis of interior decoration materials is a critical fire safety evaluation that determines the ignitability, flame spread, heat release, and smoke production of wall, ceiling, floor, and textile finishes used in buildings. This article explains the main classification frameworks (GB 8624, EN 13501-1, ASTM E84, ISO methods), typical sample requirements, key testing items, laboratory test procedures, and practical applications, helping manufacturers, architects, and contractors select materials that comply with mandatory fire protection codes.
Technical Overview
Interior decoration materials, including wall coverings, ceiling panels, flooring, curtains, upholstery fabrics, and insulation layers, are frequently the first fuels involved in a building fire. Their reaction-to-fire behavior largely determines how quickly a compartment fire develops, how far flames and smoke propagate, and how much time occupants have to evacuate. Combustion performance analysis is therefore a mandatory step in material qualification: it measures ignitability, flame spread, heat release, smoke production, and the generation of flaming droplets, and assigns a standardized fire performance classification that designers, contractors, and regulators can rely on.
The principal classification frameworks used by accredited third-party laboratories around the world include GB 8624-2012 in China, EN 13501-1 in Europe, and ASTM E84 / UL 723 in North America, supported by international ISO test methods. Under GB 8624-2012, building and decoration products are classified as follows:
- Class A (subdivided into A1 and A2): non-combustible materials that make negligible contribution to fire load and flame development.
- Class B1 (subdivided into B and C): flame-retardant materials that resist ignition and limit flame spread.
- Class B2 (subdivided into D and E): combustible materials that burn readily once ignited.
- Class B3 (level F): highly flammable materials with no demonstrated fire performance.
The European EN 13501-1 Euroclass system (A1, A2, B, C, D, E, F) follows a similar philosophy and adds classifications for smoke production (s1 to s3) and flaming droplets and particles (d0 to d2). In North America, the ASTM E84 / UL 723 Steiner tunnel test classifies interior finishes by Flame Spread Index and Smoke Developed Index, where Class A corresponds to FSI 0 to 25, Class B to 26 to 75, and Class C to 76 to 200. Which class is acceptable for a given project depends on occupancy type and location within the building, as specified by design codes such as GB 50222-2017, the Chinese code for fire safety in interior decoration design.
Testing Samples
Samples must be representative of the commercial product, taken from normal production lots, and tested in the same thickness, density, and substrate configuration as intended for end use. Before testing, specimens are conditioned in a standard atmosphere, typically 23 ± 2 °C and 50 ± 5 % relative humidity, until moisture equilibrium is reached. Because different test methods require very different specimen sizes, laboratories usually request both full-size panels and small coupons from the same batch.
Wall and Ceiling Finish Materials
This group includes wallpapers and wall fabrics, decorative paints and coatings, plywood and MDF panels, PVC and aluminum-plastic composite panels, gypsum boards with decorative laminates, acoustic panels, and wood-plastic cladding. For Single Burning Item testing, specimens consist of two wings, typically 1500 mm × 1000 mm and 1500 mm × 500 mm, while single flame source tests use strips of approximately 250 mm × 90 mm.
Flooring Materials
This group covers carpets and carpet tiles, vinyl and LVT flooring, laminate and engineered wood flooring, raised-access floor panels, and sports flooring. Radiant panel testing of floor coverings uses specimens of approximately 1050 mm × 250 mm, exposed to a defined heat flux gradient to determine the critical heat flux at flame extinguishment.
Decorative Textiles
Curtains, drapes, vertical blinds, upholstery fabrics, and bedding textiles are tested primarily for vertical flame spread, after-flame time, after-glow time, and char length using specimens of approximately 300 mm × 80 mm, supplemented by limiting oxygen index strips for material screening.
Thermal Insulation and Composite Products
Expanded and extruded polystyrene, polyurethane and PIR foam boards, glass wool, rock wool, and metal-faced sandwich panels require non-combustibility furnace cylinders (approximately 45 mm diameter × 50 mm height), cone calorimeter coupons of 100 mm × 100 mm, and full-thickness wall or roof assemblies mounted as in real construction.
Testing Items
Depending on the target classification and end use, combustion performance analysis of interior decoration materials typically covers the following items:
- Ignitability: time to ignition and sustained flaming under a small flame or radiant heat source.
- Flame spread: lateral flame spread distance over the specimen surface and, for floorings, the critical heat flux at extinguishment.
- Heat release: peak heat release rate, total heat release within 600 seconds, fire growth rate index (FIGRA), and gross heat of combustion.
- Smoke production: smoke production rate, total smoke production, smoke growth rate index (SMOGRA), smoke density grade, and specific optical density.
- Burning behavior: flaming droplets and particles, mass loss, furnace temperature rise, after-flame and after-glow times, and char length.
- Combustion gas toxicity: yields of carbon monoxide, carbon dioxide, hydrogen cyanide, and hydrogen chloride from smoldering and flaming decomposition.
- Intrinsic flammability indices: limiting oxygen index (LOI) and auto-ignition temperature for screening and formulation comparison.
Testing Methods
Non-Combustibility and Gross Heat of Combustion
Class A (non-combustible) verification relies on the ISO 1182 / GB/T 5464 furnace test, in which cylindrical specimens are held at 750 °C while mass loss, sustained flaming duration, and furnace thermocouple temperature rise are recorded. This is combined with the ISO 1716 / GB/T 14402 bomb calorimeter, which determines the gross heat of combustion; products exceeding the specified heat-of-combustion thresholds cannot be classified as non-combustible regardless of furnace behavior.
Single Burning Item (SBI) Test
The EN 13823 / GB/T 20284 SBI test is the core method for intermediate classes such as B1 (B, C) and B2 (D). Two vertical wings are mounted in a corner configuration and exposed to a 30 kW propane burner. Oxygen consumption calorimetry and optical smoke measurement yield FIGRA, THR600s, lateral flame spread, and SMOGRA, which directly determine the classification grade and the additional smoke and droplet classifications under EN 13501-1.
Single Flame Source Ignitability Test
The EN ISO 11925-2 / GB/T 8626 test applies a small diffusion flame at 45 degrees to the bottom edge or surface of a specimen for 15 or 30 seconds. A material passes when the flame tip does not reach the 150 mm gauge mark within the prescribed time and burning droplets do not ignite filter paper below the specimen. This test underpins the E and B2 level classifications and is also applied to floorings and linings.
Cone Calorimeter Testing
The ISO 5660-1 / ASTM E1354 cone calorimeter exposes 100 mm × 100 mm specimens to irradiance levels of 25 to 75 kW/m² and measures heat release rate by oxygen consumption. It provides peak heat release rate, total heat released, effective heat of combustion, mass loss rate, and smoke release rate, and is widely used for research and development, fire hazard modeling, and comparative screening of flame-retardant formulations.
Surface Burning and Flooring Tests
The ASTM E84 / UL 723 Steiner tunnel exposes a 7.32 m long specimen to a controlled flame in a horizontal tunnel to determine the Flame Spread Index and Smoke Developed Index used for North American interior finish acceptance. For floor coverings, the ISO 9239-1 / GB/T 11785 radiant panel test determines the critical heat flux at which flame spread ceases; higher values indicate better performance and are required for corridors and escape routes.
Smoke Density, Toxicity, and Supplementary Methods
Smoke behavior is quantified using the GB/T 8627 smoke density test and the ASTM E662 NBS smoke chamber, which measure light transmittance through accumulated smoke. Fire effluent toxicity is assessed under GB/T 20285 by analyzing gas concentrations from decomposing specimens. Supplementary methods include the limiting oxygen index test (ISO 4589-2, ASTM D2863, GB/T 2406.2) and the GB/T 5455 vertical flame test for textiles, which are used for quality control and material development.
Applications
Combustion performance test reports and classification certificates are used throughout the lifecycle of a decoration project:
- Regulatory compliance: demonstrating that wall, ceiling, and flooring finishes meet the class requirements of GB 50222-2017, EN 13501-1 based regulations, or model building codes for specific occupancies.
- High-risk occupancies: material qualification for hotels, shopping malls, theaters, hospitals, schools, airports, and high-rise buildings, where evacuation routes and crowded spaces demand A-class or B1-class finishes.
- Product certification and export: obtaining CE marking under the European system, North American listings, or Chinese fire product conformity marks through accredited third-party laboratories.
- Engineering acceptance: providing documentation for construction quality inspection and fire safety acceptance before handover.
- Research and development: optimizing flame-retardant additives, smoke suppressants, and composite structures to achieve a target classification cost-effectively.
- Fire risk assessment: supplying input data for fire dynamics simulation and performance-based fire safety design.
FAQ
Which GB 8624 class is required for interior decoration materials?
It depends on the building occupancy and the location of the material. Evacuation staircases, refuge floors, and machine rooms generally require Class A materials; ceilings and walls of crowded rooms such as auditoriums and shopping malls typically require Class A or B1; ordinary guest-room finishes may allow B1 or B2. The specific limits are defined in GB 50222-2017 and must be confirmed against the approved fire design.
Is passing a small-flame test sufficient to prove B1 classification?
No. Under GB 8624-2012, B1 (levels B and C) classification requires the Single Burning Item test under GB/T 20284 in combination with the ignitability test under GB/T 8626. The small flame test alone supports only the lower E-level or B2 classification.
Do thin decorative layers on non-combustible substrates need separate testing?
Not always. Codes recognize that coatings, paints, and wallpapers applied in thin layers with limited mass per unit area over Class A substrates do not significantly change fire behavior, and simplified treatment is permitted when the defined thickness and mass-per-area conditions are met. Borderline cases should be confirmed with an accredited third-party laboratory or the code authority.
What sample quantities and lead times should be expected?
SBI testing requires several sets of full-height wings plus spare specimens, while cone calorimeter, LOI, and ignitability tests need only small coupons. After conditioning, a full classification sequence for a wall or flooring product typically takes one to three weeks, depending on the number of tests and any retesting triggered by borderline results.
Can European EN 13501-1 results be used directly for GB 8624 classification?
The underlying test methods, such as the SBI and single flame source tests, are closely aligned, but the classification boundaries and acceptance criteria differ between the two systems. A Euroclass B report cannot automatically be reported as GB 8624 B1; the data must be re-evaluated or the test repeated according to the applicable standard.
