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What is the difference between A1 and A2 Fire Ratings?

Reading High-Rise Fire
Source: BBC

Changes to Document B have caused us to think more about the specification of materials for buildings over 11M. The amendment banned the use of all combustible materials on the external face of buildings over 18m in height. To be compliant, materials have to achieve either A2-s1 or A1 fire ratings in accordance with BS EN 13501-1:2007+A1:2009.  Whilst both A1 and A2 materials are comply with this regulation, it is important we can define the difference.

Fire Regulations

It is important to understand the process of fire testing in order for products to pass British Standard tests regarding fire and protection and the Euroclass rating the product receives once tested. The Euroclass system of classification is made up of stacked levels, i.e as you move up a class (e.g D to C), the compliance rules get more stringent. For materials and components, classification rules are based on ‘Resistance to Fire’ and ‘Reaction to Fire’

See below insight in to how grades are awarded:

A1 vs A2 Materials

Steel masonry support

A1 materials are completely non-combustible while A2 materials have very limited combustibility. While A1 materials have no contribution to fire, A2 materials have limited contribution to fire.

Stringent tests must be passed in order for construction products to reach a Class A rating. As above, A1 rated products do not require additional safety tests given they are completely non-combustible. Examples of these materials include stainless steel, aluminium, natural stone, concrete and porcelain. These materials are only A-rated in their raw form e.g if they havent been treated in anyway. For example, applying a powder coating to aluminium may affect the fire performance rating.

To be used in a building, materials will usually need to pass the British Standards relating to Fire Protection. In particular, only A1 and A2-rated materials can be specified on buildings over 11m due to their non-combustible properties.

Smoke Emission During Combustion

The second classification in the Euroclass system relates to smoke emission. The rating S1,S2 OR S3 indicates highest to lowest performance. Classifications are not provided for products with an E or F rating.

S1 = Very limited smoke

S2= Limited Smoke

S3= A lot of smoke

Production of flaming droplets / particles 

This rating is indicated by d0, d1 or d2 from highest to lowest performance. E-rated products receive a D2 flaming droplet classification. It is important to understand that A1 rated materials are not given a rating as they do not contribute to fire growth or spread, and will not produce any smoke or droplets to receive this classification.

D0= No Burning Droplets/Particles

D1= Limited Burning Droplets/Particles

D2= Unlimited Burning Droplets/Particles

At Firma, these fire ratings are important to us. We use A1 fire rated materials, primarily stainless and mild steel, to produce our Masonry Support systems, Wind Posts and Cavity Trays. Ancillaries such as thermal breaks are A2 fire rated (these materials are exempted from the ban).

Next Steps

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Whilst this industry insight is designed to cover the main considerations, there may be other considerations when designing your solution based on a specific project and its requirements. It would always be essential to consult with qualified professionals to ensure the appropriate design to suit your specific application. Firma aims to offer technical support on a project-by-project basis. Get in touch with the team today to discuss your current or up-coming project!