The testing for flame retardancy of materials follows specific standards and procedures. Here is a general overview of the commonly used methods for testing flame retardant properties:

1. Vertical Burn Test (ASTM D6413): This test evaluates the flammability of textiles, films, and other flexible materials. A vertically oriented test specimen is exposed to a small flame at the bottom for a specified duration. Parameters such as flame spread, charring, and afterflame time are measured and compared to the requirements of the standard.

2. Limiting Oxygen Index (LOI) Test (ASTM D2863): This test determines the minimum concentration of oxygen required to support combustion. The test specimen is placed in a vertical chamber while the oxygen concentration is reduced until the material stops burning. The LOI value indicates the material's flame retardant properties; a higher LOI value indicates better flame retardancy.

3. Cone Calorimeter Test (ISO 5660, ASTM E1354): This test measures the heat release rate, smoke production, and other fire-related parameters of materials. The specimen is exposed to controlled radiant heat, and various measurements, such as heat release rate and total smoke release, are recorded. These values can be used to assess the flame retardant performance of the material.

4. Horizontal Burn Test (UL 94): This test is mainly applied to plastics. The test specimen is subjected to a small flame ignition and assessed based on criteria such as burn rate, dripping, and self-extinguishing properties. The UL 94 classification ranks materials from V-0 (most flame-resistant) to V-2 or HB (less flame-resistant).

5. Oxygen-Index Tube Test (ISO 4589-2): This method determines the minimum oxygen concentration required to sustain combustion. The test specimen is placed vertically inside a tube, and the oxygen concentration is reduced until the material stops burning. The oxygen index value is calculated and used to assess the flame retardant properties.

6. 45-Degree Flammability Test (FAR 25.853): This test is specific to materials used in aircraft interiors. It evaluates the flame resistance of textiles, foams, and composites. The test involves exposing the specimen to a small flame at a 45-degree angle and assessing its burn rate, propagation, and self-extinguishing properties.

It's important to note that specific industries or regulations may have their own flame retardancy testing standards. When conducting flame retardant testing, it is crucial to follow the prescribed standards and procedures to ensure accurate and reliable results.