The ASTM E84-23c standard specifies a test method for the surface combustion characteristics of building materials. It is mainly used to evaluate the flame spread and smoke generation properties of materials under fire conditions. The test uses a Steiner tunnel furnace. The sample is placed in a ceiling position and exposed to an ignition source. The flame spread index (FSI) and smoke development index (SDI) are calculated by measuring the flame spread distance and smoke concentration. The standard is applicable to building materials with exposed surfaces such as walls, ceilings, etc., such as decorative materials, thermal insulation materials, etc. The test results are used for material grading, such as Class A (FSI ≤ 25), Class B (26 ≤ FSI ≤ 75), and Class C (76 ≤ FSI ≤ 200). In the North American market, interior materials need to pass this test before they can be applied to construction projects.