Once a building fire breaks out, it often causes catastrophic consequences within minutes. The rapid spread of flames, heat, and toxic fumes is the primary cause of casualties and property damage. Passive fire protection, as the "first line of defense" for building safety, automatically limits the spread of fire, keeps escape routes unobstructed, and protects the structural integrity of the building through the design of materials, components, and systems, without human or electrical intervention.

Unlike active fire protection systems (such as automatic sprinklers, smoke detectors, and fire extinguishers), passive fire protection relies on the inherent characteristics of the building itself, with fire-resistant materials being the most crucial element. These materials must remain non-combustible, non-disintegrating, and non-conductive under extreme temperatures, providing occupants with an escape window of 30 minutes to several hours, buying valuable time for fire rescue.

To ensure the actual performance of fire-resistant materials, they must be verified through internationally recognized standardized testing and classification systems. The European standards EN 13501 series, EN 1363-1, and ISO 834-1, along with the American standards ASTM E119 and UL 263, the British standard BS 476, and the Japanese standard JIS A 1304, collectively form the global framework for refractory material assessment. These standards largely rely on specialized fire resistance furnaces to simulate real fire temperature profiles, thereby quantifying the material's reaction to fire and fire resistance.

This article will systematically introduce the role of refractory materials in passive fire protection, their main types, key testing and classification standards, a comparison of major global standards, practical cases, and future trends, providing a comprehensive reference for architects, engineers, material manufacturers, and fire safety professionals.

The Basic Principles of Passive Fire Protection and the Dual Role of Refractory Materials

The core objective of passive fire protection is to achieve "three controls" through fire compartmentation, structural protection, and smoke control:

1.Controlling the spread of flame and heat

2.Maintaining the integrity and load-bearing capacity of building components

3.Preventing toxic fumes from entering escape routes and adjacent areas

(Figure 1: Schematic diagram of a passive fire compartmentation system, illustrating how components such as firewalls, fire doors, wall penetration seals, and fire-resistant dampers work together to limit the spread of fire and smoke.)

Refractory materials play "two key" roles here:

1.Reaction to Fire: Assessing whether the material is easily ignited in the early stages of a fire, whether it contributes to the fire's spread, and whether it produces large amounts of smoke or molten droplets. Typical classification standards include EN 13501-1 (A1 highest non-combustible grade → F highly combustible), ASTM E84 (Flame Spread Index and Smoke Development Index), BS 476 Part 7, etc. Materials with low reaction to fire (such as A1 grade) can significantly slow the early development of a fire.

2.Fire Resistance: Examining how long a material or component can maintain its load-bearing capacity (R), integrity (E, preventing flame penetration), and insulation (I, limiting temperature rise on the unexposed side) under standard fire conditions. Common classifications include EN 13501-2 (EI/REI + minutes,e.g., EI 60 indicates integrity and insulation maintained for 60 minutes), ASTM E119/UL 263 (hours), and BS 476 Part 20-24.

Only materials possessing both excellent fire reactivity and high fire resistance can truly become a reliable component of passive fire protection systems.

Testing Standards, Test Equipmnet and Classification Systems of Refractory Materials

Performance verification of refractory materials relies on standardized fire simulation tests. Mainstream testing methods include:

ISO 834-1 / EN 1363-1: Standard cellulose fire curve (room temperature → 945°C & 60min → approximately 1100°C & 180min), used to test the fire resistance of walls, doors, beams, columns, seals, etc.

ASTM E119 / UL 263: American standards, with curves similar to ISO 834, but slightly different load application and failure criteria.

UL 1709: Hydrocarbon fire curve (extremely rapid temperature rise, reaching 1100°C in just 5 minutes), commonly used in high-risk scenarios such as petrochemical plants and tunnels.

BS 476 series: Traditional British standards, now largely superseded by EN standards, but still widely used in Commonwealth countries and parts of Asia.

(Figure 2: The Vertical furnace for fire resistance)

(Figure 3: The horizontal furnace for fire resistance)

The EN 13501 series is the core standard for fire resistance classification of European building products:

EN 13501-1: Fire-response classification, addressing the material's contribution to the fire's initial spread. The classification is based on a combination of test methods, including:

EN ISO 1182 (Non-combustibility test, A1/A2 level)

(Figure 4: ISO 1182 non-combustibility test furnace)

EN ISO 1716 (Total calorific value test, A1/A2 level)

(Figure 5: ISO 1716 Bomb Calorimeter)

EN 13823 (Small Intake Biology (SBI) test, A2-D level)

(Figure 6: ISO 13823 SBI)

EN ISO 11925-2 (Small Intake Ignition Test, below E level)

(Figure 7: ISO 11925 Single-Flame Source Test)

EN ISO 9239-1 (Floor Radiant Heat Test, for flooring only)

(Figure 8: ISO 9239 Flooring Radiant Panel Test)

ISO 5660-1 (Cone Calorimeter test, for heat release and smoke production data of B-D level products, is one of the auxiliary test methods for categories B-D in EN 13501-1.)

(Figure 9: ISO 5660 Cone calorimeter)

The following are common refractory material types and their performance under major standards:

(Figure 10: Table of Types, Test Standards and Classification Systems for Refractory Materials)

(Figure 11: Schematic diagram of the working principle of intumescent fire-retardant coating - when exposed to fire, the coating expands rapidly to form a thick carbonized layer, effectively isolating heat and protecting the steel structure.)

In actual testing, these materials typically need to meet both fire-resistance and fire-fighting requirements, and obtain market access through third-party certifications (such as CE marking, UL certification, Intertek, Applus+, etc.).