| | Classification | Class A (0-25 FSI), Class B (26-75 FSI), and Class C (76-200 FSI). All classes have a maximum SDI of 450.
| Class A (0-25 FSI) | A Class A fire rating, with a Flame Spread Index (FSI) of 0-25, is the highest fire-resistance rating for building materials. It signifies a low ability for fire to spread, typically found in materials like brick, gypsum wallboard, and certain fire-retardant treated materials.
Flame Spread Index (FSI):
This is a measure of how quickly a fire spreads across a material's surface, with 0-25 being the lowest, indicating the best resistance.
Class A materials: These materials are highly resistant to fire and are often used in areas with high fire risk, such as hospitals and schools.
ASTM E84 (Steiner Tunnel Test): This test, used to determine FSI and SDI (Smoke Development Index), is a standard for assessing fire resistance in building materials.
NFPA 255: Another standard that, along with ASTM E84, is used to assess fire-resistance ratings.
Smoke Development Index (SDI): Class A materials also have a low SDI, typically 0-450, meaning they produce minimal smoke during combustion | | Class B (26-75 FSI) | A Class B fire rating, with a Flame Spread Index (FSI) between 26 and 75, indicates that a material has moderate flame resistance and a moderate ability to spread flames. This means that while it's more fire-resistant than Class C materials, it's not as resistant as Class A materials
ASTM E84 (Steiner Tunnel Test): This standard test is used to determine the flame spread index of building materials.
Flame Spread Index (FSI): This is a numerical rating that indicates how quickly flames will spread across a material's surface.
Class A (0-25 FSI): These materials have the lowest flame spread and are considered highly fire-resistant.
Class B (26-75 FSI): These materials offer moderate fire resistance and are suitable for situations where a higher level of flame resistance is needed than Class C but not as high as Class A.
Class C (76-200 FSI): These materials have the highest flame spread and the least fire resistance.
| | Class C (76-200 FSI) | A Class C fire rating, with a Flame Spread Index (FSI) between 76 and 200, indicates materials that allow flames to spread more quickly and have a lower fire resistance compared to Class A (0-25 FSI) or Class B (26-75 FSI) materials.
Class C Fire Ratings: Materials with a Class C fire rating are considered to have a moderate to high flame spread, meaning flames can propagate more easily across their surface.
Flame Spread Index (FSI): The FSI is a numerical value that indicates how quickly flames spread across a material's surface, with higher values representing faster flame spread.
Class C FSI Range: Materials in the Class C category have an FSI between 76 and 200, according to HandiSOLUTIONS.
Examples of Class C Materials: Examples of materials that might fall into Class C include certain types of plywood, fiberboard, hardboard siding, and some faster-burning wood types.
ASTM E84 Test: The FSI is determined through the ASTM E84 standard test, which evaluates the surface burning characteristics of building materials.
International Building Code (IBC): The IBC uses fire rating classifications, like Class C, to ensure materials used in construction meet specific fire safety requirements.
International Building Code (IBC) Standards: Materials must clearly label their FSI and smoke developed number (SDI) to meet IBC standards, according to Curtis Lumber & Plywood.
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