What are fire ratings and what do they mean?

Fire ratings are classifications which inform the user how fire-resistant different materials are.

In a nutshell: 

  • Fire ratings show the flammability of different materials.
  • Classifications are split into three parts: reaction to fire, smoke propagation and the amount of flaming droplets produced.
  • Reaction to fire classifications range from A1 (non- combustible) to F (highly-flammable).
  • An example of a full fire rating would be ‘A2,s1,d0’.

Fire ratings use an alphanumerical system to define the classification; starting with A1, meaning non-combustible, and ending with F which means the material is easily flammable.

Furthermore, ratings according to the BS EN13501-1 are broken down into three categories: reaction to fire, smoke propagation and number of flaming particles produced.

S stands for the total smoke propagation:
S1 = a little or no smoke
S2 = quite a lot of smoke
S3 = substantial smoke

D relates to the number of flaming droplets produced during the first 10 minutes of the material’s exposure to fire:
D0 = none
D1 = some
D2 = a lot

A table of the different classifications and their reactions to fire can be seen below. 

Classification  How it responds to fire Examples
A1 Non-combustible meaning there is no contribution to fire. Brick, stone, terracotta, concrete, anodised aluminium, mineral wool.

Non-combustible although, unlike A1, it can produce smoke or flaming droplets. Only A1 and A2 materials can be used on high rise properties.

PPC aluminium and fibre-cement.
B Very limited contribution to fire and high resistance to spreading. Treated wood.
C Effective against medium fire exposure with limited contribution to fire.
Plywood and fibreboard.

Capable of resisting a small flame with medium contribution.

Different types of wood.
E Can resist a small flame but only for a limited time. High contribution to fire. Soft fibrewood, expanded polystyrene and polyurethane, both with flame retardants.
F Materials that have either not been tested or have not met the requirements of the other classes therefore are likely to be easily flammable. Extruded polystyrene and expanded polyurethane without flame retardants.

An example of a full fire rating is as shows:


This rating indicates that the material is non-combustible, produces little or no smoke and no flaming droplets and particles.

All information regarding regulations and ratings were correct at time of publication. Read BS EN 13501-1 for more information. Always consult a fire safety expert before specification.

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