Rob Wakefield, Technical Manager – Fire Protection at ROCKWOOL®, discusses the difference between the reaction to fire and the resistance to fire.
Specifiers need to give careful consideration to the potential fire risk in buildings, with particular emphasis put on compartmentation to allow safe evacuation, reduce the risk of fire spread within the building and to enable access for fire fighters.
To be able to achieve this, it is important to understand the difference between the two types of fire classification related to the fire properties of the insulation material they are specifying and the building elements its included within. Fire properties are measured in two key ways, Reaction to fire and Resistance to fire, there is often confusion between what these two mean, and what the differences are.
There is a clear difference, but it just needs an explanation. So, let’s start with the definitions:
- Reaction to fire – the measurement of how a material or system will contribute to the fire development and spread, particularly in the very early stages of a fire, when evacuation is crucial.
- Resistance to fire – the measurement of the ability of a material or system to resist, and ideally prevent, the passage of fire from one distinct area to another. Every element that is deemed to have to be fire resistant, whether it is the door, floor, roof or wall, is tested.
Why are these measures important?
Reaction to Fire
The contribution of a product to a developing fire, in terms of ease of ignition, energy produced and flame spread will have an impact on how easy it is for people to escape from the area of the fire.
When at the specification stage, it is important for contractors to consider how the material will react to a fire. Primarily they should be asking whether the material has a Euroclass Rating.
At a fundamental level the Euroclass system separates products into two groups i.e.:
Non-combustible: Made of material that does not burn if exposed to fire.
Combustible: Able to catch fire and burn easily.
But, how do these terms combustible and non-combustible relate to building materials?
The European Reaction to Fire classification system (Euroclasses) is the EU harmonised standard for assessing the qualities of building materials in the event of exposure to fire. This standard is a legal requirement for CE marked construction products and relevant for both the United Kingdom and the Republic of Ireland.
As the name suggests, this classification system assesses and rates the ‘reaction to fire’ performance of construction products, providing a clear and simple method for comparing the performance of products when exposed to fire.
When products are tested according to the Euroclass system a range of factors are investigated: ignitability, flame spread, heat release, smoke production and propensity for producing flaming droplets/particles. The Euroclass system is accepted by all European Union States (and is mandatory where there is a Harmonised Product Standard) and includes seven classification levels, from A1 to F.
Understanding these Euroclass classifications is vitally important.
The Euroclass system states that products achieving A1 classification are defined as non-combustible under these Regulations. Products achieving an A2 classification are recognised as products of limited combustibility, offering “no significant contribution to fire growth”.
Products achieving a rating of B-F are deemed to be combustible. Where a product has not been measured for fire safety under the Euroclass system then it will be classed as F, meaning no performance declared (NPD).
So, in short, non-combustible equals non-combustible.
Other terms typically used by the industry to describe product performance, such as, fire safe, fire proof, fire retardant or flame proof do not define that the product is non-combustible. ”Non-combustible” is a legally defined term within the Building Regulations. Only materials achieving the highest standard of reaction to fire can be certified non-combustible.
So, how can you determine the Euroclass rating of a product’s combustibility?
In the case of thermal insulation, all products should be CE marked against the appropriate harmonised standard. The Harmonised Product Standard for mineral wool is BS EN 13162:2012. (issued on 28 February 2013).
Whichever harmonised standard is applicable, by law, all manufacturers must have their products independently tested to verify performance claims. Once a product has been CE marked, the manufacturer, must make publicly available a Declaration of Performance (DoP). The DoP is a legal document in which the manufacturer identifies the product and its intended use, indicating compliance in relation to the relevant Harmonised Product Standard and performance in relation to specified “essential characteristics”.
It’s in the DoP that you can determine a product’s Euroclass rating. The declared value on the CPD DoP will match one of the Euroclasses. For ROCKWOOL® stone wool insulation, you will find an A1 rating meaning non-combustible.
Euroclasses arise from classification systems for ‘reaction to fire’ performance of construction products. It provides a common method for comparing the performance of products in a fire.
Stone wool insulation can achieve a reaction-to-fire rating of A1 under the British and European standard for the fire classification of construction materials BS EN 13501-1: 2007, or non-combustible.
Resistance to Fire
A resistance to fire rating is harder to achieve, as this involves large scale testing of building elements to verify how they react when exposed to a simulated flashover fire exposure. The common ratings for fire resistance provide an indication of the time that the element will resist a fire for, typically ranging from 30 minutes to 240 minutes. The resistance is typically measured in two key forms; Integrity (E) and Insulation (I), we will briefly explain what these are:
- Integrity – measures the ability of the element to prevent flames and hot gases spreading from the fire side to the non-fire side. Preventing the spread of flames and hot gases, stops fire spreading and allows valuable time for escape.
- Insulation – measures the ability of the element to prevent the heat from the fire passing from the fire side to the non-fire side of the element. Preventing the transfer of this heat stops items on the non-fire side from combusting and creating a further fire.
The appropriate classification of a building material, whether it be an insulation product or a fire protection product, is critical to correctly meet the appropriate regulatory requirements. During the various stages from design through to installation, care should be taken, to ensure that those with an influence over the eventual product installed, understand the fire properties of the material and why they are vital for the fire safety of the building.
Learn more about the ROCKWOOL Firepro® product range here.