Vertical Flammability Chamber，ASTM D6413-99

The vertical flammability chamber is a laboratory instrument specifically designed to evaluate the vertical burning performance of plastics, non-metallic materials, textiles, and wires and cables. This equipment is widely used for quality testing and flame-retardant classification of products such as flame-retardant clothing, flame-retardant fabrics, electronic and electrical components, and automotive interior materials. Modern vertical flammability chambers feature automated control, precise timing, and automatic ignition. Most current models employ PLC (Programmable Logic Controller) and touchscreen interfaces for easy parameter settings, and can automatically record and store flame application time, afterflame time, and afterglow time. The instrument is typically equipped with specimen clamps, a Bunsen burner, and a gas supply system. Some models integrate both horizontal and vertical testing modes. Key parameters such as flame angle (e.g., 0°, 20°, 45°) and flame height can be adjusted according to standard requirements.

Working Principle

The vertical flammability chamber simulates material behavior under actual fire conditions. Using a standardized flame source (such as a Bunsen burner) at a specific flame height and angle, the vertically mounted specimen is exposed to fire for a predetermined duration. The flammability and fire hazard classification are then evaluated based on ignition behavior, burning duration, and flame length.

The testing procedure generally involves:

Using a Bunsen burner with a specified nozzle diameter (e.g., 9.5 mm), adjusting the flame to the required height (e.g., 20 mm or 40 mm) and angle (0° or 45°).

Positioning the bottom of the vertically clamped specimen in the flame for a set time (e.g., 10 seconds).

Automatically or manually recording the flaming combustion time, afterflame (no-flame) time, afterglow time, and burning length.

Structural Composition

The vertical flammability chamber consists of the following main components:

1. Test Chamber System:

Provides a sealed or semi-sealed environment for testing, usually with a glass observation door and internal illumination. Some units are equipped with exhaust or fume treatment systems.

2. Flame Source and Gas Supply System:

Core component is a standardized Bunsen burner, typically with a nozzle diameter of 9.5 mm ±0.3 mm and an effective length of ~100 mm. The system includes a gas source, pressure regulators, flow meters, pressure gauges, solenoid valves, and high-voltage automatic ignition. Flame height and angle are key adjustable parameters.

3. Specimen Clamping and Positioning System:

Stainless steel clamps secure the specimen, often integrating both horizontal and vertical testing. Some units include motorized drives for precise automatic or manual adjustment of the specimen relative to the flame.

4. Control System:

Usually a “PLC + touchscreen” design, controlling flame application time, afterflame time, afterglow time, ignition, gas flow, and angle adjustment.

5. Data Acquisition and Timing System:

Integrated high-precision timers automatically record and store all burning time parameters. Some models may include thermocouples for temperature monitoring.

6. Safety Protection System:

Includes combustible gas leakage alarms, automatic exhaust, safety interlocks, and flame monitoring to ensure safe operation.

Operation Procedure

Specimen Preparation:

Strip specimens: 125 mm ±5 mm length, 13 mm ±0.5 mm width.

Plate specimens: 150 mm ±5 mm length, 150 mm ±5 mm width.

Condition specimens under standard climate conditions (e.g., 23°C ±2°C, 50% ±5% RH) for at least 24–48 hours.

Equipment Calibration:

Adjust Bunsen burner flame height (e.g., 20 mm ±2 mm for V-level tests, 40 mm ±2 mm for 5V-level or automotive interior tests).

Set timing parameters for flame application, afterflame, and afterglow according to testing standards (e.g., UL 94).

Mount the specimen vertically, ensuring the longitudinal axis is perpendicular, and adjust the clamp so the specimen bottom is at the specified distance from the burner tip (e.g., 10 mm for V-level, 40 mm for 5V-level, or 20 mm for automotive interior tests).

Align the flame center with the specimen bottom using motorized or manual adjustment.

Testing Procedure:

Activate automatic ignition to apply the flame to the specified position. After the set flame application time, the system automatically removes the flame.

For multi-flame tests (e.g., UL 94 V-level), reapply the flame after the first afterflame extinguishes according to the standard.

The system records afterflame and afterglow times, while the operator observes and records burn length, dripping behavior, and ignition of the cotton substrate below.

Flame-retardant classification (e.g., V-0. V-1. V-2. HB, 5V, FV-0. FV-1. FV-2) is determined according to the recorded parameters and relevant standards.

Any non-compliant specimen in a set requires additional testing as per the standard.

Ventilation and Safety:

Exhaust system should be on before and after testing.

Use high-purity gas (e.g., methane ≥98%).

No flammable materials should be placed inside the chamber. Do not operate exhaust during testing to avoid flame disturbance.

Maintenance and Management2

Regular Maintenance: Inspect burners, gas lines, motors, and clean internal dust to ensure proper operation and prevent energy waste.

Operator Training: Personnel must be trained in proper operation and energy-saving practices. Strict adherence to procedures prevents damage and ensures accurate results.

Application Fields

Industrial Testing: Evaluate flame-retardant fabrics for clothing and textiles.

Certification Review: Used for technical audits in safety certifications and production licenses.

Research and Development: Analyze vertical burning behavior of plastics and non-metallic materials.

The vertical flammability chamber tests the burning characteristics of materials in a vertical orientation, including burn length, burning time, self-extinguishing behavior, and dripping. It evaluates flame-retardant performance of textiles, plastics, foams, composites, and other materials, determining compliance with relevant standards. The instrument supports quality control, material modification verification, flame-retardant development, and scientific research, providing reliable data for fire safety assessment and material improvement.