NFPA 255 Standard Test Method for Surface Burning Properties of Building Materials

NFPA 255, Standard Test Method for Surface Burning Characteristics of Building Materials, published by the National Fire Protection Association (NFPA), is a critical standard used to evaluate the fire performance of building materials. This standard provides fundamental data to ensure compliance with building codes and enhance fire safety by assessing how materials contribute to flame spread and smoke generation when exposed to fire. NFPA 255 was repealed in 2011 and is now referenced in ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials. However, its historical significance and methodology remain relevant for understanding fire safety testing.

The NFPA 255 standard describes a method for testing the comparative surface burning properties of building materials that focuses on two key criteria:

• Flame spread index: Measures how quickly flames spread across the surface of a material. This index expresses the horizontal spread of flames across the surface of a test specimen. The index is scaled from 0 (non-combustible material, such as asbestos cement board) to 100 (highly flammable material, such as red oak).
• Smoke Emission Index: Measures the amount of smoke produced during combustion. It is scaled similarly and again uses red oak as a reference point.

This standard applies to materials used in interior wall and ceiling coverings, ensuring they meet fire resistance safety requirements. It is referenced by codes such as NFPA 101 Life Safety Code and various building codes to determine acceptable fire performance criteria.

The NFPA 255 test method, which complies with ASTM E84 and UL 723 "Testing the Surface Burning Characteristics of Building Materials," utilizes the widely accepted Steiner tunnel test. The test procedure includes:

• Test apparatus: A material sample, 61 cm wide and 7,5 m long, is placed in a Steiner tunnel lined with firebrick. Two burners provide approximately 89 kW of energy to ignite the sample.
• Flame spread assessment: The rate at which flames spread across the material surface is compared with two reference materials (usually red oak and cement board) to calculate the flame spread index.
• Smoke measurement: The amount of smoke generated is measured using a photoelectric cell to obtain the smoke generation index. To meet NFPA Class A standards, the smoke generation index value must not exceed 450.

This test method simulates real-world fire conditions to determine how materials behave in terms of flame spread and smoke production, which are critical factors in assessing fire risk in buildings.

The NFPA Technical Committee withdrew NFPA 255 because it was deemed technically equivalent to ASTM E84. Since then, ASTM E84 has become the primary standard, and references to NFPA 255 are directed to it. This consolidation ensures consistency among model building codes and standards. ASTM E84 is often referred to as ASTM E84 25/50 due to its flame spread and smoke development criteria.

The NFPA 255 standard (and its successor, the ASTM E84 standard) are critical for:

• Building code compliance: Materials used in construction, such as insulation, wall cladding and ceiling linings, must meet flame spread and smoke generation criteria to comply with regulations such as the international building code.
• Material selection: Architects, engineers, and builders use test results to select materials that increase fire safety, especially for high-risk structures such as high-risk buildings or healthcare facilities.
• Fire safety design: This standard ensures that materials contribute minimally to the spread of fire and smoke, reducing risks to building occupants and first responders.

The NFPA 255 standard plays a crucial role in reducing fire risks by rigorously testing building materials for their fire performance. This standard helps protect life and property by establishing clear criteria for flame spread and smoke generation. For example, materials rated Class A (flame spread index not exceeding 25 and smoke generation index not exceeding 450) are considered highly fire-resistant, making them suitable for use in structures requiring stringent fire safety measures, such as hospitals or high-rise buildings.

The NFPA 255 test method has been widely used in building codes, fire safety regulations, and architectural specifications for years. Materials are classified according to their test performance as follows:

• Class A (or Class I): Flame spread 0-25
• Class B (or Class II): Flame spread 26-75
• Class C (or Class III): Flame spread 76-200

These classifications helped make decisions about where materials could be used safely, such as in corridors, exits, or high-traffic areas.

Despite its widespread use, the Steiner tunnel test has several limitations:

• It only tests surface burning, not how materials behave in three-dimensional or structural fire scenarios.
• Charred or melted materials may perform differently than in real fires.
• The test is not suitable for floor coverings or wall assemblies with complex geometries.

For these reasons, other fire tests defined in “NFPA 286 Standard fire test methods for evaluating the contribution of wall and ceiling interior coatings to room fire growth” or “ASTM E1354 Standard test method for heat and visible smoke release rates for materials and products using oxygen consumption calorimetry” may be used depending on the application.

As a result, while NFPA 255 is no longer an active standard, it continues to exist through ASTM E84, which maintains the same rigorous testing methodology. Understanding this standard provides insight into the evolution of fire safety standards and the importance of evaluating building materials for flame spread and smoke production. By adhering to these standards, the construction industry can achieve safer buildings and compliance with modern fire regulations.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with NFPA 255, Standard Test Method for Surface Burning Properties of Building Materials.