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Fire safety is a crucial aspect of building design and construction. One of the key factors that influences fire safety is the flame spread classification of the materials used in the building. This article will explain what flame spread classification is, how to select the appropriate class for different occupancies, and provide real-world examples of materials and their classifications, with a special focus on evacuation routes.

The purpose of such testing is to provide architects and fire protection engineers with adequate information so that they can select appropriate materials that will not contribute to the problem of life safety from fire within structures. The speed of flame over surface interior material can affect the safety of people within a building if the flame spreads faster than evacuation can be accomplished or if fire spreads throughout an entire building before adequate fire protection measures can extinguish the blaze.

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Flame spread refers to the rate at which a fire can spread across the surface of a material. It is measured in a standardized test, and the results are used to classify materials into different flame spread classes. These classifications provide valuable information about the fire performance of materials and help guide their use in different building applications.

The most commonly used flame spread classification system is the ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Materials. This standard classifies materials into four categories based on their flame spread index (FSI) and smoke developed index (SDI):

There are two major flame-spread classification systems used worldwide:

? ASTM E84 (I, II, and III): This is the most common system used in North America. It assigns materials a flame spread index (FSI) ranging from 0 to 450, with 0 being the best (no flame spread) and 450 being the worst (fastest flame spread).

? EN 13501-1: This system is widely used in Europe and other parts of the world. It classifies materials into seven Euroclasses (A1, A2, B, C, D, E, and F) based on their flame spread rate, smoke production, and flaming droplets/particles.

(i) Class I (A): 0–15 materials have the slowest flame spread and are considered the most fire-resistant. They are often required for use in the interior walls and ceilings of high-occupancy buildings such as schools, hospitals, and office buildings.

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Class A fire ratings include fire-resistant building materials such as:

? Concrete

? Brick and stone

? Fire-retardant-treated wood

? Fire-resistant insulation

? Fire-rated doors and windows

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(ii) Class II (B): 26-75) materials have a moderate flame spread rate and are acceptable for use in some interior applications. In low-occupancy buildings, they may be permitted for walls and ceilings, though they might be restricted in high-occupancy areas.

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Class B fire ratings are typically used for materials such as:

? Lower-grade fire-retardant wood

? Some types of foam insulation

? Certain types of roofing materials

(iii) Class III (C): 76–200 materials have a faster flame spread rate and are considered combustible. Their use is typically limited to exterior applications or non-critical interior areas with appropriate fire protection systems in place.

Class C fire ratings are typically used for materials such as:

? untreated wood, like plywood, fiberboard, and certain siding materials.

? Some types of interior finishes

? Nowadays, with today’s fire codes, there are fewer types of roofing materials on certain commercial buildings.

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The appropriate flame spread classification for a material depends primarily on the building's occupancy. Buildings with high occupant densities require materials with a higher level of fire resistance, while low-occupancy buildings may have more flexibility in material selection.

Here's a general guideline for selecting the appropriate flame spread class based on occupancy:

Additional factors to consider:

? Type of construction: Buildings with wood framing may require materials with a higher flame spread rating than buildings with steel framing.

? Fire protection systems: Buildings equipped with sprinkler systems or other fire suppression systems may have more flexibility in material selection.

? Local building codes: Always consult with local building codes for specific requirements and regulations regarding flame spread classification.

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Understanding the flame spread classification of materials is particularly important for evacuation routes. These routes need to be constructed with materials that will minimize the spread of fire and smoke, allowing people to safely exit the building in case of an emergency.

Here are some examples of materials commonly used in evacuation routes and their corresponding flame spread classifications:

It's important to note that this is not an exhaustive list, and the specific materials used in evacuation routes will vary depending on the building code requirements and the specific design of the building.

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(i) BNBC 2020, Page No. 2754: Materials having a structural base of non-combustible materials as defined in this Code and having a surface not over 3.2 mm thick that, when tested by the provisions of this Code, has a flame spread rating not higher than 50 (fifty).

(ii) BNBC 2020, Page No. 2761: 3.1.18 Insulation: The provisions of this Section apply to thermal and acoustical insulations located on or within floor-ceiling and roof-ceiling assemblies, crawl spaces, walls, partitions, and insulation on pipes and tubing. Materials used for such insulation and covering shall have a flame spread rating of not more than 25 and a smoke density of not more than 450.

(iii) BNBC 2020, Page No. 2872:? 2.8 Surface Finishes

(a) The fire susceptibility of various types of surface finishes shall be determined in terms of the rate of spread of fire (ASTM E 84). Based on the rate of

spread of fire, the surface finish materials shall be classified into three (3) classes:

? Class I(A) Surfaces of low flame spread: Flame does not effectively spread more than 300 mm in the first 1.5 minutes with an ultimate value of 600 mm.

? Class II (B) Surfaces of medium flame spread: flame does not spread effectively more than 300 mm and 850 mm in the first 1.5 minutes and 10 minutes, respectively.

? Class III(C) Surfaces of rapid flame spread: Flame spreads effectively more than 300 mm and 850 mm in the first 1.5 minutes and 10 minutes, respectively.

(b) The interior finish of walls and ceilings shall have a flame spread rating not greater than those in Table 4.2.2 for various occupancy classes.

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Understanding flame spread classification is essential for ensuring fire safety in buildings. By selecting the appropriate materials based on their flame spread ratings and complying with local building codes, architects, engineers, and construction professionals can create safer buildings for occupants. Remember, the goal is to minimize the spread of fire and smoke, allowing everyone to evacuate safely in case of an emergency.