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Fire Ratings Explained

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Fire Ratings Explained

Passive Fire Protection, Testing, and Standards

In order to comply with building regulations, measures to subdue the spread of fire to other parts of a building must be taken. In terms of components and coatings for the walls and ceilings, there are two key measures of fire testing.

These measures are concerned with;

1. Reaction to Fire - Retardancy

Reaction to Fire (Retardancy) is the measurement of the ability of a material to resist or prevent the passage of fire from one area to another.

2. Reaction to Fire and Structural Integrity

Reaction to Fire – structural Integrity is the measurement of how a material will contribute to the fire being able to develop.


When deciding on the correct coating system to provide Fire protection to a combustible material such as timber, it is essential that the products meet the standards set out by the new Euroclass System for the fire safety classification of building materials.

The test methods are totally new and involve exposing the product to direct flame and is called the Single Burn Test or SBI Test.

This test is designed to simulate the flame exposure that would be experienced by material lining the walls of a room when a "wastepaper basket" ignites next to the wall in the corner of a room.

The test measures a Fire Growth Rate (FIGRA), the heat energy contribution to the fire from the product. The result is categorised on a Fire Growth Rate Index.

A second measurement is taken to calculate the volume of smoke produced by the fire and categorised according to a Smoke Growth Rate (SMOGRA) index.

Finally, the test also measures oxygen consumption as well as carbon dioxide and carbon monoxide production. These gas concentrations help identify the heat release and the burning characteristics of the tested products.

The Standards to the Euroclass system are referred to as;

European standard - EN 13501-1 reaction to fire classification with parts

BS EN 13823: 2010+A1:2014 single burn test (SBI)


BS EN11925-2:2010 single flame ignitability test (SFI).

Classification of individual products

To provide guidance to the user/specifier regarding the performance of a particular product under test. Information is provided by the following process:

There are seven Reaction to Fire classes.

A1     The Product is classed as a Non-Combustible
A2 Limited Combustibility
B Combustible materials – Very Limited contribution to fire
C Combustible materials – Limited contribution to fire
D Combustible materials – Medium contribution to fire
E Combustible materials – High contribution to fire
F Combustible materials – Easily flammable

These classes are further divided to provide information on a product’s tendency to produce smoke and flaming droplets / particles based on the results of the SBI Test.

Smoke Generation

Smoke generation is measured for Reaction to Fire classes A2 to D. Smoke emission classifications are not provided for products with an E or F overall rating.

There are three smoke intensity levels:

s1     Emissions absent or very little
s2 Emissions with average volume intensity
s3 Emissions with high volume intensity

Fire Generation

Burning droplets/particles can inflict skin burns and cause further spread of fire. Burning droplets/particles are measured for Reaction to Fire classes A2 to E. E-rated products receive a d2 flaming droplet classification. F-rated products receive none.

There are three classes of burning droplets:

d0     No burning droplets
d1 Slow dripping droplets
d2 High/Intense dripping droplets

As an example:

Our Envirograf Fire Protection Coatings have been tested to this new standard with the resulting highest classification.


This translates to:

  • B - Combustible materials – Very Limited contribution to fire
  • s1 - Smoke emissions absent or very little
  • d0 - No burning droplets

Classification according to European Standard EN-13501-1 

Non-combustible materials: No contribution to fire    


Limited combustibility

A2 - s1 d0

A2 - s2 d0

A2 - s3 d0

A2 - s1 d1

A2 - s2 d1

A2 - s3 d1

A2 - s1 d2

A2 - s2 d2

A2 - s3 d2

Combustible materials: Limited contribution to fire

B - s1 d0

B - s2 d0

B - s3 d0

B - s1 d1

B - s2 d1

B - s3 d1

B - s1 d2

B - s2 d2

B - s3 d2

Combustible materials: Minor contribution to fire

C - s1 d0

C - s2 d0

C - s3 d0

C - s1 d1

C - s2 d1

C - s3 d1

C - s1 d2

C - s2 d2

C - s2 d2

Combustible materials: Medium contribution to fire

D - s1 d0

D - s2 d0

D - s3 d0

D - s1 d1

D - s2 d1

D - s3 d1

D - s1 d2

D - s2 d2

D - s3 d2

Combustible materials: High contribution to fire E E - d2
Combustible materials: Easily flammable F


Reaction to fire and structural integrity is the measurement of how a material will contribute to the fire being able to develop.

30 and 60 Minute Fire Integrity Fire-resistant materials and coatings are specifically developed to meet a particular level of fire protection.

A surface or building component that has been treated correctly will be protected from the effects of a fire by a protective system that has been tested to remain intact and protect the building component for at least 30, 60, 90 or 120 minutes, dependent upon which level is chosen.

Fire protection components and coatings are normally used on structural elements of a building and services that run through designated firewalls to help maintain its integrity during a fire.

These treated areas also allow the emergency services more time to control the outbreak of a fire and can delay the spread of a fire to other adjoining rooms and buildings.

Testing the reaction to fire

The test method measures the ability of a material (intumescent) to prevent the penetration of fire through a structure (for example doors or floor joists that bear the overall floor load) to maintain its structural integrity.

The test is run in accordance with BS 476 Parts 20-23 (1989) and components are given classifications with specific periods of time achievements, such as 30 or 60 minutes integrity.

Typically, coatings and building components use intumescent materials to meet these standards.