Chinese Fire Standard GB 8624: Guide to the 2012 and 2025 Editions

Fire-resistant building materials are the fundamental barrier against fire spread, ensuring structural integrity and safe personnel evacuation. The scientific rigor of their classification and the rationality of their application scenarios directly dictate a building’s overall fire safety performance.

Based on authoritative codes such as the current Chinese Fire Standard GB 8624-2012 (Classification for burning behavior of building materials and products) and GB 50016-2014 (2018 Edition), and looking ahead to the comprehensive updates in the upcoming GB 8624-2025 mandatory standard, this article systematically analyzes the Chinese architectural fire classification system. We clarify technical fire protection requirements across various scenarios and outline scientific material selection principles, providing comprehensive compliance and technical support for international architectural design, construction, and global building material procurement from China.

Core Classification Standards for Fire-Resistant Building Materials (GB 8624-2012)

The classification of building fire materials in China relies on the GB 8624-2012 standard as its core technical basis, adopting a comprehensive evaluation system of “Main Classification + Additional Classification.”

Based on flame-retardant performance, the main GB 8624 fire rating is divided from highest to lowest into four classes: Class A (Non-combustible), Class B1 (Flame retardant / hardly flammable), Class B2 (Combustible / normally flammable), and Class B3 (Easily flammable). Among them, Class A is further subdivided into two sub-classes: A1 and A2.

The additional classification parameters cover three critical metrics: smoke density (production), flaming droplets/particles, and smoke toxicity. Together, these elements achieve a full-dimensional evaluation of a fire protection material’s combustion behavior.

Core Metrics and Definitions of Main Classifications

Class A (Non-combustible materials): Exhibits no combustion characteristics and is a mandatory choice for critical fire protection zones in buildings. It is further subdivided into two sub-classes: A1 and A2.

Class A1

The ultimate non-combustible rating. The core metrics require a gross calorific value (PCS) of ≤ 2.0 MJ/kg, a total heat release of ≤ 1.5 MJ, and absolutely no sustained flaming phenomena. Typical materials include inorganic non-combustible materials such as granite, stainless steel panels, and rock wool boards.

Class A2

The quasi-non-combustible rating. Core metrics require a gross calorific value (PCS) of ≤ 3.0 MJ/kg, a total heat release of ≤ 4.0 MJ, and a sustained flaming time of ≤ 20 seconds. Typical materials include fire-rated gypsum boards and premium inorganic composite non-combustible materials such as calcium silicate boards and fiber cement boards.

Class B1

Possesses excellent flame-retardant properties and self-extinguishes rapidly once the fire source is removed. Core technical metrics dictate that the oxygen index for plastic materials must be ≥ 32%, average furnace temperature rise ≤ 140°C, average mass loss ≤ 80%, and no flaming droplets ignite the filter paper within 600 seconds. Typical materials include fire-retardant plywood, fire-retardant coated wood, and B1-rated flame-retardant carpets.

Class B2

Exhibits a slower burning rate with baseline flame-retardant capabilities. Core metrics dictate an oxygen index of ≥ 27% for plastics, with the ability to self-extinguish after the fire source is removed. Typical materials include fire-retardant polyurethane foam, treated fabrics, and B2-rated decorative wall panels.

Class B3

Lacks any flame-retardant properties, ignites extremely easily, and is strictly prohibited from being used in critical building fire protection zones. Typical materials include standard untreated wood, unmodified plastics, and non-fire-retardant synthetic fabrics.

Additional Classification Requirements of GB 8624-2012

A complete GB 8624 fire rating label must include additional performance indicators. A standard format example under the Chinese Fire Standard GB 8624 is “B1-s1, d0, t0”. The meanings and technical requirements for each specific parameter are detailed below:

• Smoke Production (s – Smoke density): Divided into three levels: s1 (low smoke), s2 (medium smoke), and s3 (high smoke). High-occupancy venues should prioritize s1 low-smoke materials.
• Flaming Droplets/Particles (d): Divided into three levels: d0 (no droplets), d1 (droplets present but do not ignite), and d2 (droplets ignite). Materials utilized in evacuation routes and pedestrian corridors must meet the stringent d0 or d1 requirements.
• Smoke Toxicity (t): Divided into three levels: t0 (non-toxic), t1 (low toxicity), and t2 (toxic). Spaces designated for long-term personnel stays, such as residential buildings, hospitals, and schools, must achieve t0 or t1 smoke toxicity requirements.

GB 8624-2012 Fire Rating Requirements for Different Architectural Scenarios

The fire protection requirements for various building scenarios are established based on the Code for fire protection design of buildings (GB 50016) and the Code for fire prevention in design of interior decoration of buildings (GB 50222-2017). The core philosophy strictly follows the “risk matching” principle: the higher the fire risk level and occupant density of a space, the more stringent the technical requirements for the GB 8624 fire rating of the materials utilized.

(I) Critical Structural Components of Buildings

Core Load-Bearing Components

It includes fire walls, load-bearing walls, columns, beams, floor slabs, and evacuation stairs. They must utilize Class A non-combustible materials. Building components with a Class I fire resistance rating require a fire resistance limit of ≥ 3.0h, while those with a Class II rating require ≥ 2.0h (for example, steel structural components must be coated with thick intumescent fire-retardant coatings to ensure structural stability in high-temperature environments).

Curtain Walls and Exterior Wall Insulation Systems

The combustion performance rating of insulation materials shall not be lower than Class B1. When Class B1 or B2 insulation materials are applied to exterior walls, a Class A fire barrier (firestop) must be installed. The barrier width must be ≥ 300 mm and tightly fitted to the wall structure to ensure the effectiveness of the fire compartmentation.

(II) Building Interior Decoration Elements

1. Ceilings:

• Underground buildings (including underground garages, subterranean malls, etc.), smoke-proof stairwells, and anteroom ceilings: Mandatory use of Class A non-combustible materials.
• High-rise civil buildings (including residential and office buildings) ceilings: The fire rating should not be lower than Class B1.
• Single-story and multi-story civil buildings ceilings: Standard usage areas may use Class B2 materials, but densely populated venues such as shopping malls and schools must use ceiling materials with a fire rating no lower than Class B1.

2. Walls (Wall Linings):

• Evacuation corridors and fire compartmentation partition walls: Mandatory use of Class A non-combustible materials.
• Wall surfaces in high-rise civil buildings: The fire rating should not be lower than Class B1 (moisture-prone areas like kitchens and bathrooms must use Class A non-combustible materials).
• Interior walls within residential units: Class B2 materials are permitted, but high fire-risk areas like kitchens and balconies must have a wall fire rating no lower than Class B1.

3. Floors:

• Specialized venues such as underground malls and hospital inpatient ward floors: The fire rating should not be lower than Class B1.
• Standard residential and office space floors: Class B2 materials are permitted. However, public spaces like waiting halls and business halls must meet a minimum Class B1 rating.

(III) Special Functional Spaces

High-Occupancy Venues

• Underground/semi-underground venues: Ceilings and wall surfaces must use Class A non-combustible materials; the combustion performance rating of floors and other decorative elements must not be lower than Class B1.
• Above-ground venues: Ceiling combustion performance must be at least Class B1, while walls and floors must be at least Class B2. The use of Class B3 easily flammable materials is strictly prohibited.
• Evacuation Routes (including stairwells, corridors, safety exits, etc.): Ceilings, walls, and floors must all utilize Class A non-combustible materials under the Chinese Fire Standard GB 8624. Decorative materials within these routes must not encroach upon the required evacuation width and must strictly avoid generating flaming droplets or toxic smoke.
• Equipment Rooms (including power distribution rooms, fire control centers, generator rooms, etc.): Ceilings, walls, and floors must all utilize Class A non-combustible materials. The combustion performance rating of cable trays and pipe wrapping materials inside the equipment room must achieve Class B1 or higher.

Selection Principles and Practical Operational Requirements for Fire-Resistant Building Materials under GB 8624-2012

(I) Core Selection Principles

• Principle of Compliance: Prioritize building materials backed by valid Type Approval Certificates for Fire Products and official testing reports strictly conforming to the GB 8624-2012 standard. Ensure that all classification metrics are authentic and valid, resolutely preventing “fake fire-resistant” materials from entering the construction project.
• Principle of Adaptability: Select materials precisely based on scenario-specific GB 8624 fire rating requirements, environmental conditions (moisture, high temperature, corrosion), and functional needs (load-bearing, thermal insulation, decoration). For example, prioritize high-temperature-resistant Class A rock wool for hot equipment rooms, and utilize moisture-resistant Class A materials in humid environments.
• Principle of Eco-Friendliness: Prioritize eco-friendly fire protection materials that are low-smoke, low-toxicity, and halogen-free to avoid the release of toxic gases like chlorine or hydrogen bromide during combustion. Specifically, materials utilized in high-occupancy venues must meet the stringent t0 or t1 smoke toxicity requirements outlined in the Chinese Fire Standard GB 8624.
• Principle of Economy: While strictly satisfying mandatory fire rating requirements, strategically balance material costs with construction costs. For instance, Class B2 flame-retardant wallpaper can be safely used for standard residential walls, avoiding the cost redundancies caused by unnecessarily pursuing Class A materials where not mandated.

(II) Practical Operational Points for Material Selection

• Verify Material Test Reports: Focus heavily on verifying whether the main classification, additional classifications (s, d, t), and fire resistance limits in the supplier’s report meet your project’s specific design requirements. Confirm that the test report is within its validity period and that the issuing testing institution possesses CMA (China Metrology Accreditation) and CNAS (China National Accreditation Service for Conformity Assessment) qualifications. This ensures the test results are internationally recognized and authoritative.
• Focus on Construction Compatibility: Ensure the selected fire-resistant materials coordinate and adapt seamlessly with other building components. For instance, intumescent fire coatings must have excellent adhesion to substrates (steel, wood), and insulation materials must connect flawlessly with fire barriers (firestops) to eliminate weak points in the building’s fire compartmentation.
• Consider Long-Term Stability: Select fire-resistant materials that are anti-aging and deformation-resistant. For example, exterior wall insulation materials must possess strong UV resistance and rainwater erosion resistance, ensuring that their fire performance does not degrade over long-term exposure.
• Strict Prohibition of Non-Compliant Substitution: It is strictly forbidden to substitute Class B1 or Class A materials with inferior Class B2 materials. In particular, critical components such as core structural elements and evacuation routes must strictly follow building code requirements. The specified fire rating must never be arbitrarily downgraded to cut costs.

Introduction to the Upcoming GB 8624-2025 Update

On December 31, 2025, the mandatory national standard Classification for burning behavior of building materials and products (GB 8624-2025) was officially published. Proposed and managed by the National Fire and Rescue Administration, it is set to be officially implemented on January 1, 2027, comprehensively replacing the older GB 8624-2012 version.

Full Establishment of the 4D Evaluation System

The new standard completely breaks away from single-dimensional evaluations. While retaining the traditional four basic levels (Class A Non-combustible, B1 Flame retardant, B2 Combustible, B3 Easily flammable), it formally establishes a strict “4D Evaluation System”. This system mandates the comprehensive assessment of four dimensions:

• Combustion Performance (The core foundation)
• Smoke Production Characteristics (s-rating)
• Flaming Droplets/Particles (d-rating)
• Smoke Toxicity (t-rating)

The “Strictest Exclusive Rules” for Building Insulation Materials

In response to frequent fires caused by insulation materials in recent years, the updated standard establishes the most stringent, exclusive regulatory rules specifically for building insulation materials and products. Insulation materials are now meticulously sub-categorized and subjected to precise grading, effectively eliminating material misuse and the substitution of inferior goods at the source.

Newly Covered Fields for the First Time

To keep pace with modern architectural technologies, GB 8624-2025 includes materials from emerging sectors under mandatory supervision for the very first time. Most notably, it explicitly covers the fire performance testing and classification requirements for Photovoltaic (PV) modules, filling a critical regulatory gap for new-energy building materials.

The “Rigid Safety Red Line” for High-Occupancy Venues

For high-occupancy venues, the new standard draws an impassable “rigid safety red line”. It requires not only compliance with the main fire classification but also strictly mandates that additional indicators meet the highest safety limits: s1 (extremely low smoke), d0 (no flaming droplets), and t0 (non-toxic). This maximizes escape visibility and protects human life during a fire emergency.

Summary of the GB 8624-2025 Code

The new standard introduces a systematic upgrade centered around five core concepts: “expanding scope, refining classifications, elevating dimensions, strengthening applications, and promoting traceability”:

1. Reconstructed a 3D, 9-Category System: Building insulation materials are now explicitly detailed as an independent major category, further subdivided into five sub-categories (walls, roofs, floors, pipes, and double-sided sandwich composite panels).
2. Elevated Smoke Production to a Core Metric: Smoke production characteristics have been upgraded from merely “additional information” to a core component of the classification, forming a strict four-dimensional evaluation model: Combustion Performance + Smoke Production + Flaming Droplets + Smoke Toxicity.
3. New Testing Methodologies: Introduced several new test methods, including the welding spark test and specific fire performance evaluations for photovoltaic (PV) modules.
4. Strict Traceability Requirements: Proposed the “Three-Same Principle” (same sample, same test, same report) for architectural insulation materials, and mandated the implementation of QR codes and electronic tags to ensure full-chain quality traceability.

Why Does GB 8624-2025 Classify Materials into A1, A2, B, C, D, and E?

For practical architectural engineering applications and design specifications, the standard retains the four conventional, widely understood domestic grades: A (Non-combustible), B1 (Flame retardant), B2 (Combustible), and B3 (Easily flammable).

However, A1, A2, B, C, D, and E represent the highly specific laboratory testing classifications. The exact correlation between the two systems is as follows:

1. A1, A2 → Class A (Non-combustible)
2. B, C → Class B1 (Flame retardant)
3. D, E → Class B2 (Combustible)
4. F → Class B3 (Easily flammable; note that the 2025 version no longer uses Class F as a formal identification label).

The transition to this 6-tier laboratory classification system is driven by three critical factors:

1. The Objective Laws of Fire Development

The evolution of a building material fire progresses through distinct stages: no ignition → extremely hard to ignite → limited fire spread upon ignition → rapid fire spread → violent combustion.

• A1 / A2: Release almost no heat and do not combust. A1 represents the most stringent criteria, while A2 allows for an extremely minute amount of heat release.
• B / C: Can be ignited, but both heat release and flame spread are strictly restricted, categorizing them as flame retardant.
• D / E: Easily ignited with rapidly diffusing flames, categorizing them as combustible.

This 6-tier system segments the continuous risk of fire—from completely non-combustible to easily flammable—into precise gradient steps. It accurately distinguishes performance nuances, resolving the flaw of the traditional 4-tier system where materials with vastly different actual fire behaviors were lumped into the same category.

2. International Standard Harmonization (Referencing EN 13501-1)

This specific A1-A2-B-C-D-E-F testing architecture originates directly from the European building material fire standard, EN 13501-1. By adopting this universally recognized classification system, domestic Chinese testing reports can seamlessly interoperate with international evaluation frameworks. This significantly facilitates the global export of building materials, PV modules, and decorative fabrics. Concurrently, retaining the traditional A/B1/B2/B3 nomenclature ensures compatibility with established Chinese architectural design habits.

3. Alignment with the 4D Evaluation System (Combustion + Smoke + Droplets + Toxicity)

The new standard goes beyond simply evaluating whether a material burns; it simultaneously evaluates three critical secondary indicators: smoke production (s), flaming droplets (d), and smoke toxicity (t).

• Complete Classification Example: B1 (B-s1, d0, t1)
• While the letters A1/A2/B/C/D/E describe heat release and flame propagation (the direct danger of the fire), the s/d/t parameters supplement the evaluation by addressing secondary fire hazards: smoke inhalation, molten debris, and toxic gases.

A coarse 4-tier system simply cannot provide the granularity needed to match the stringent threshold criteria of the s/d/t additional classifications. Only a 6-tier laboratory testing framework can correspond one-to-one with these supplementary metrics, realizing a truly comprehensive four-dimensional evaluation.

Analyzing the Major Changes in GB 8624-2025

1. Significant Changes in Material Classification

The cascade of changes in GB 8624-2025 originates from a fundamental restructuring of material classifications.

Compared to the current standard, the broad term “Building Materials” has been revised to “Building Materials and Products,” and explicitly incorporates roof covering materials/products and building insulation materials/products. Building insulation materials and products are now definitively divided into 5 sub-categories: wall insulation, roof insulation, floor insulation, double-sided sandwich composite insulation, and pipe insulation. Furthermore, “Building Products” has been reclassified into two major categories: “Decorative Materials and Products” and “Non-Metallic Materials and Products for Equipment,” with the notable addition of photovoltaic (PV) modules.

Crucial Note for Procurement: Because the new standard alters not only the classification criteria but also the grading requirements, all existing test reports based on the 2012 standard will eventually need to be re-evaluated and re-issued.

Clarification Rules:

• Flat materials and products applied to floors or roof coverings must be categorized under flooring materials or roof covering materials, respectively.
• If flat materials, flooring materials, or roof covering materials are applied specifically for architectural insulation, they must be classified under building insulation materials and products.

2. The Multiplicity of Material Fire Ratings

Conventional wisdom suggests that a single material maintains a constant fire rating regardless of its application. For example, a B1-rated insulation material is assumed to be B1 whether used on a floor, roof, or wall.

However, the new Chinese Fire Standard GB 8624-2025 completely updates this common sense: The exact same material can achieve entirely different fire ratings when used in different architectural locations! This occurs because different categories of materials are now subject to different testing protocols and grading thresholds.

• Example: Consider an organic insulation material with an Oxygen Index of 26%. Based solely on this metric, if applied as a roof or floor insulation layer, it achieves a GB 8624 Class B1 (Flame retardant) rating. However, if that identical material is applied as wall insulation or pipe insulation, it is downgraded to a Class B2 (Combustible) rating.

Thickness Dependency: Even within the exact same material category, the GB 8624 fire rating is intrinsically linked to material thickness. The new standard specifies an interpolation rule: For a series of identical materials varying only in thickness, if both the maximum and minimum thicknesses achieve the same fire rating, all intermediate thicknesses are deemed to meet that rating. Therefore, if a supplier only provides a test report for a 50mm insulation board, but your project requires a thickness greater than or less than 50mm, the material must undergo mandatory re-testing.

Key Takeaway: The combustion performance rating of a material or product is strictly dependent on both its application category and its thickness. This introduces a multiplicity to material fire ratings that engineers must carefully verify.

3. Direct Certification Method for Class A1 (Exemption from Testing)

How do you classify a composite panel where two metal sheets are bonded together with adhesive? The metal is Class A1, but the adhesive is typically Class B3. Under the old standard, the entire “composite panel” required full-scale assembly testing to determine its final rating.

GB 8624-2025 introduces a massive regulatory improvement here: For concrete, mineral wool, fiberglass, lime, metals (e.g., iron, steel, copper), gypsum, putty, calcium silicate materials, natural stone, glass, ceramics, and other homogeneously dispersed materials, if the contained organic matter does not exceed 1% (by mass fraction or volume fraction), the material is directly deemed to meet Class A1 requirements without requiring a fire test.

Furthermore, for products layered and composited from one or more of the above materials, if the organic binder content does not exceed 0.1% (by mass fraction or volume fraction), the product is directly deemed to meet Class A1 requirements.

Because the specific gravity of adhesives is generally much lower than that of metal or dense inorganic boards, the difference between mass fraction and volume fraction is significant. However, since the standard offers an “or” relationship (mass or volume), calculations can be based on volume fraction, meaning the vast majority of these high-quality composite assemblies can now be directly certified as Class A1.

Conclusion

Understanding the GB 8624 fire rating system is non-negotiable for international developers, architects, and procurement managers sourcing building materials from China. The impending shift from GB 8624-2012 to the highly stringent GB 8624-2025 marks a critical milestone, moving China’s regulatory framework into full structural harmonization with the European EN 13501-1 standard. For global buyers, this means Chinese test reports will soon offer unprecedented transparency and international interoperability.

Whether you are specifying materials for high-occupancy venues, specialized industrial facilities, or exterior cladding, staying ahead of this compliance curve is essential. By partnering with forward-thinking manufacturers and prioritizing premium Class A1 non-combustible materials, international projects can guarantee regulatory compliance, mitigate supply chain risks, and deliver uncompromising fire safety in any global market.