The ASTM E-84 fire rating is a standard test method for determining the surface burning characteristics of building materials. The test measures a material's flame spread and smoke development characteristics when exposed to a heat source under controlled conditions. The ASTM E-84 test is widely used in the United States and is required by building codes in many jurisdictions.
The test is conducted in a chamber that is 20 feet long, 25 inches wide, and 25 feet high. The test material is mounted at the end of the chamber on a frame with a maximum size of 4 feet by 8 feet. The material is positioned in such a way that it is faced with the heat source, which is a gas-fired conical flame burner.
The flame source is positioned at the base of the test sample and generates heat with a heat flux of 50 kW/m2. The test sample is exposed to the flame for 10 minutes. During this time, two parameters are observed: flame spread and smoke developed.
Flame spread is defined as the rate at which flame travels across the surface of the test material. The rate of flame spread is measured in relation to a standard control material such as untreated red oak flooring. The control material is assigned a flame spread rating of 100. A material that has a flame spread rating of 25, for example, is considered to be four times less likely to spread flames across its surface than the control material.
Smoke developed is a measure of the amount of smoke that the test material produces. The test measures the optical density of the smoke produced as the material is exposed to the heat source. The optical density is measured in relation to the amount of smoke produced by untreated red oak flooring, which is assigned a smoke developed rating of 100. A material that has a smoke developed rating of 50 is considered to produce half the amount of smoke as the control material.
The results of the flame spread and smoke developed tests are combined to create a single ASTM E-84 fire rating. This rating is expressed as a Class A, B, or C rating, with Class A being the highest rating and Class C being the lowest.
To achieve a Class A rating, the material must have a flame spread rating of 0-25 and a smoke developed rating of 0-450. To achieve a Class B rating, the material must have a flame spread rating of 26-75 and a smoke developed rating of 0-450. To achieve a Class C rating, the material must have a flame spread rating of 76-200 and a smoke developed rating of 0-450.
It is important to note that some materials, such as those made of foam plastics, may not be able to achieve a Class A rating due to their inherent flammability characteristics. These materials may still meet building code requirements for use in certain applications if they achieve a Class B or C rating and are used in accordance with other code requirements.
In addition to the ASTM E-84 fire rating, there are other fire tests and ratings used to evaluate building materials. Some commonly used tests include the NFPA 266 test, which measures the fire performance of draperies and other window treatments, and the UL 94 test, which measures the flammability of plastic materials.
In summary, the ASTM E-84 fire rating is a standard test method used to evaluate the surface burning characteristics of building materials. The test measures a material's flame spread and smoke developed characteristics when exposed to a heat source under controlled conditions. The results of the flame spread and smoke developed tests are combined to create a single fire rating expressed as a Class A, B, or C rating.