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Fire resistance levels are specified in building codes globally. This system supersedes old fire ratings and provides an accurate method of predicting how a wall maintains its strength in a fire and resists its spread. The fire resistance level (FRL) specifies the fire resistance periods (FRP) for structural adequacy, integrity, and insulation. These components are described below.
This is the ability of a wall to continue to perform its structural function.
Integrity is the ability of a wall to maintain its continuity and prevent the passage of flames and hot gases through cracks in the wall.
This is the ability of a wall to provide sufficient insulation where the side of the wall away from the fire does not exceed a predefined rise in temperature.
Fire Resistance Level
The fire resistance level is expressed in minutes for each of these periods and always in the same order. For example, an FRL of 90/90/90 means a fire resistance period of 90 minutes each for structural adequacy, integrity, and insulation.
Factors Influencing Fire Resistance Level
The fire resistance level of a wall depends not only on its thickness but also on its height, length, and boundary conditions (i.e., how it is connected to other building elements). Therefore, it is impossible to give an FRL for a particular brick as the fire resistance period for structural adequacy is specific to the wall type and its boundary support conditions.
This article was updated on 7th February, 2020.