Understanding Fire Resistance Ratings (FRR / FRL)
A practical guide to what fire resistance ratings mean, how ratings like --/60/-- and --/60/60 are read, and why passive fire penetrations are not described as 60/60/60.
What is a fire resistance rating?
A fire resistance rating describes how long a building element can continue to perform during fire exposure. The rating is usually written in three parts and may be referred to as FRR or FRL depending on the context used.
Fire resistance ratings are commonly used for fire-rated walls, floors, doors, shafts and service penetrations. The purpose of the rating is to show how the element performs against specific fire criteria for a measured period of time such as 30, 60 or 120 minutes.
The rating is normally expressed in three positions. These positions relate to structural adequacy, integrity and insulation.
What the three parts mean
A fire resistance rating is written in this order: structural adequacy / integrity / insulation.
Structural adequacy
This refers to the ability of a building element to continue carrying load during a fire without collapse.
Integrity
This refers to the ability of the element to resist the passage of flames and hot gases through the separation.
Insulation
This refers to the ability of the element to limit heat transfer from the fire side to the non-fire side.
How to read common fire ratings
The numbers show the number of minutes the element is intended to satisfy the required criteria.
What does -- / 60 / -- mean?
This is a very common way of describing passive fire penetrations and service openings.
In the rating -- / 60 / --, the first position is shown as double dash because the penetration system is not a structural element. It is not intended to carry building load during a fire.
The middle position of 60 means the system is intended to maintain integrity for 60 minutes. This means it helps resist the passage of flames and hot gases through the opening.
The final position is shown as double dash where insulation is not part of the required rating for that tested system or application.
What does -- / 60 / 60 mean?
Some passive fire systems need to satisfy both integrity and insulation requirements.
In the rating -- / 60 / 60, the penetration still has no structural role, which is why the first position remains double dash.
The second 60 means the system maintains integrity for 60 minutes, while the third 60 means it also limits heat transfer for 60 minutes. This may be relevant where the tested system or required performance includes both integrity and insulation.
This is why some passive fire penetrations are described as -- / 60 / -- while others may be described as -- / 60 / 60. The correct description depends on the tested system and the required fire performance.
Why passive fire penetrations are not described as 60 / 60 / 60
This is one of the most important distinctions in passive fire terminology.
Passive fire penetrations and fire stopping systems are generally not structural building elements. They are not intended to carry load in the same way as a fire-rated wall, floor or beam.
For that reason, describing a passive fire penetration as 60 / 60 / 60 would incorrectly suggest that the system provides 60 minutes of structural adequacy as well as integrity and insulation.
In passive fire work, the first position is therefore commonly shown as double dash. This reflects the fact that structural adequacy is not part of the penetration system’s role.
Key points to remember
Understanding the notation helps make fire ratings easier to interpret in practical passive fire work.
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