A numerical classification that measures how quickly flames spread across the surface of a material compared to standard reference materials.

Flame spread rating is a numerical classification system that measures how quickly flames spread across the surface of a building material when exposed to a standardized fire test, providing a comparative assessment of the material’s fire behavior relative to established reference standards. This critical fire safety metric is determined through laboratory testing procedures, most commonly the ASTM E84 Steiner Tunnel Test, which evaluates both flame spread and smoke development characteristics of interior finish materials. Flame spread ratings are essential for building code compliance, material selection, and fire safety design, helping architects, engineers, and building officials ensure that interior finishes and building materials meet appropriate fire safety standards for their intended applications and occupancy types.

The primary purposes of flame spread rating include providing standardized comparison of fire behavior between different materials, enabling building code compliance for interior finish materials, supporting fire safety design decisions in building construction, facilitating material selection based on fire performance requirements, ensuring occupant safety through appropriate material limitations, providing regulatory authorities with objective criteria for material approval, and establishing performance benchmarks for material manufacturers and testing laboratories.

Testing methodology for flame spread rating follows standardized procedures, primarily ASTM E84 (also known as UL 723), which involves placing a material sample in a horizontal test tunnel and exposing it to a controlled flame source while measuring the rate and extent of flame propagation across the surface. The test compares the material’s performance to two reference standards: red oak flooring (assigned a flame spread index of 100) and cement-asbestos board (assigned a flame spread index of 0), creating a scale where lower numbers indicate better fire performance.

Fun Fact: The ASTM E84 flame spread test was developed in the 1950s and uses a 25-foot tunnel that was originally designed to test aircraft materials during World War II. The red oak reference standard was chosen because it was readily available and provided consistent, reproducible results.

• Fire Rating
• HERS Rating
• K-Value Rating