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. |
| A2 |
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. |
| D |
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:
A2,s1,d0.
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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