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How is the flame spread rating determined in ASTM E84?
2023/11/08
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The flame spread rating in ASTM E84 is determined by conducting a test known as the "Steiner Tunnel Test" or "Tunnel Test." This test measures the flame spread and smoke development characteristics of building materials when exposed to a controlled fire source. Here's how the flame spread rating is determined in the ASTM E84 test:
1. Test Apparatus: The test is performed in a specially designed horizontal tunnel with dimensions and specifications defined by the ASTM E84 standard. The tunnel is lined with the material being tested, and it has a gas-fired ignition source at one end.
2. Specimen Preparation: A specimen of the material to be tested is mounted on the interior surface of the tunnel. The size of the specimen may vary based on the material type.
3. Ignition: The gas-fired ignition source at one end of the tunnel is ignited, and the flame is applied to the surface of the specimen. The flame is held against the specimen for a specified duration.
4. Observation: During the test, trained observers measure and record the following parameters:
- The flame spread distance, i.e., the distance traveled by the flame along the surface of the specimen.
- The time it takes for the flame to reach specific points along the specimen.
- The amount of smoke generated during the test.
5. Calculation: Using the data collected during the test, the flame spread rating is calculated. This rating is based on a formula that considers the rate of flame spread and the specific test conditions. The formula provides a numerical value for the flame spread index.
6. Classification: Based on the numerical value obtained from the formula, the material is classified into various flame spread classes, such as Class A, Class B, or Class C. Class A materials have the lowest flame spread, while Class C materials have the highest flame spread.
The specific criteria for classifying materials into these categories are outlined in the ASTM E84 standard, and they are based on the flame spread index calculated during the test.
The ASTM E84 test is widely used to evaluate the fire performance of building materials, and the flame spread rating is an essential factor in determining the suitability of these materials for use in various construction applications. A lower flame spread rating indicates better fire resistance and safety.
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