ASTM E84 Steiner Tunnel UL910 Flame Propagation Performance Test

The Steiner Tunnel Test, developed by UL in the 1940s, is a testing method for the "fire resistance properties" of interior finishing materials. This method uses a 25-foot (approximately 7.62-meter) long tunnel furnace to verify the surface fire spread rate and smoke characteristics of interior finishing materials.

• The Steiner Tunnel Test's prominence in the fire protection field lies in its ability to provide cost-effective, repeatable testing and the use of sample sizes that characterize interior finishing materials used in actual installations.
• Applicable to CMP-grade electrical wires, cables, and optical fibers for duct combustion testing
• Test method: Multiple samples are laid in a horizontal duct and burned for 20 minutes using an 86 kW gas Bunsen burner (300,000 BTU/Hr)
• Pass criteria: Flame extension distance does not exceed 5 feet (1525 mm) from the flame tip; Peak smoke density ≤0.5, average optical density ≤0.15
• Applicable scenarios: Suitable for cable testing installed in ventilation ducts, air handling equipment, and air recirculation pressurization systems, meeting US and Canadian certification requirements

ASTM E84: The full name is "Standard Test Method for Surface Burning Characteristics of Building Materials", developed by the American Society for Testing and Materials (ASTM).

UL 910: It is the most demanding cable standard in the UL fire protection standard, applicable to plenum cables.

• Equipment Composition: Composed of an inlet chamber, automatic inlet gate, combustion test chamber (tunnel furnace), gas burner, removable sealed top cover, exhaust transition section, exhaust duct, exhaust velocity measurement, smoke density measurement, velocity control, gas analysis system, computer data acquisition and control system, and dust purification system.
• Inlet Chamber: Material: L-shaped stainless steel plate + stainless steel structural components; Inlet dimensions: h298.5 mm × w464 mm; Inlet valve: Automatic control, closed-loop control linked to the exhaust end.
• Combustion Chamber (Tunnel Furnace): Length: 7.62 m; Bottom and Side Walls: Constructed with refractory bricks 230×115×65 mm; Top Cover: Outer Side: 6.4 mm inorganic reinforced cement board; Inner Side: 51 mm insulating mineral wool; Sealing Method: Water-filled seals on both sides of the top cover.
• Combustion System: Burner: Dual-head copper gas burner; Gas Control: Mass flow controller 0～160 L/min; Rated Combustion Power: 86 kW (300,000 BTU/Hr); Maximum Output Power: 100 kW; Ignition and Control: Computer automatic control.
• Gas Analysis System: O₂, CO₂, CO Concentration Measurement; T90 Response Time: ≤5 s.
• Smoke Density Determination: Peak maximum optical density: ≤0.5; Average optical density: ≤0.15.
• Flame Spread Determination: Flame spread distance: ≤1525 mm (5 ft).
• Control and Software: System: Windows + LabVIEW-style professional software; Control method: Fully automatic computer-aided acquisition, control, data processing, curve comparison, and Excel report output.

1. Set all control devices for the tunnel furnace operation, darken the room, and ignite the burner.
2. The observer records the distance and time it takes for the maximum flame front to pass through the tunnel observation window. If no propagation is observed, record the flame front propagation at ignition or at least every 30 seconds.
3. The test lasts for 10 minutes. Lamps and photocells installed in the exhaust duct record the smoke ash intensity during the test.
4. Record the flame spread and smoke index using calibration materials of red oak and inorganic reinforced cement board. Red oak will propagate the flame to the end of the tunnel in approximately five and a half minutes, producing a flame spread index of approximately 90. The smoke index of red oak is specified as 100. The flame spread and smoke index produced by inorganic reinforced cement board are zero.

According to Section 6-5.3 of the National Fire Protection Association (NFPA) Life Safety Standard 101, interior finishing wall and ceiling materials tested according to ASTM E84 (or NFPA 255, UL 723) are classified into three classes: Class A, B, and C.

• Class A: FSI value 0-25 and Smoke Index (SDI) less than 450
• Class B: FSI value 26-75 and Smoke Index (SDI) less than 450
• Class C: FSI value 76-200 and Smoke Index (SDI) less than 450

Materials are classified based on their tested FSI value (and smoke density). The lower the FSI value, the lower the fire hazard. For high-rise buildings and stairwells, materials with an FSI < 25 should be used. Materials with an FSI < 100 can only be used in areas with less stringent fire protection requirements, while materials with an FSI > 100 do not meet flame retardant requirements.