Fire terminology explained

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Fire terminology can be quite confusing. What does fire resistant or fire retardant mean? And what does it mean when building materials are called non-combustible, combustible or flammable?

What does non-combustible mean?

Non-combustible simply means that a material does not contribute to a fire. The gradation of non-combustibility is determined by the Euroclass system, where classes A1 and A2 are non-combustible and B-F combustible. When you use non-combustible materials, you basically design out the risk, because this material does not significantly contribute to a fire. The non-combustibility (A1, A2) is secured by setting limits to the calorific content (PCS values). For combustible materials (B-F) these limits are not set.

What are combustible materials?

Combustible materials have a higher calorific value than non-combustible materials and can therefore contribute to the spread of a fire. In the Euroclass system, classes B to F are combustible. It is important to note the meaning of the different Euroclass classifications: a B classification close to the A2 border is much safer than an F classification, which means the material hasn’t managed to pass tests for a higher class.

For high-rise and high-risk buildings, we advise to always use non-combustible materials.

Find out more about non-combustible and combustible building materials.

What does fire retardant mean?

Fire retardants are additives that are mostly used with combustible materials, to slow down the ignition of these materials. These fire retardants are consumed when exposed to a fire; they slow down the combustibility but do not reduce it.

What are flammable materials?

Flammable materials ignite more easily than other materials (such as combustibles). For example, it can burn rapidly with a flame or has a flash point below an arbitrary temperature limit of 50°C.

What does fire resistance mean?

When a fire does ignite and sets fire to a room, it brings us to the field of fire resistance. This focuses on how long we can keep the fire from spreading between separate rooms or floors (compartments) of a building. Fire resistance is therefore determined by the total engineering, construction and condition of a building. The fire resistance classification is mostly given as a time limit in minutes in which people should be able to safely escape out of a building in case of fire.

What are fire barriers or cavity barriers?

Fire barriers or cavity barriers are elements placed in the cavity of a façade to prevent the spread of fire within the cavity. One can argue that when non-combustible insulation and cladding (Euroclass A1-A2) is used, the risk of fire spread via the cavity is limited. However, the use of cavity barriers is often prescribed in national building regulations or codes. In general, fire barriers can be divided into two categories: vertical and horizontal.

What is the difference between horizontal and vertical fire barriers?

For rainscreen cladding , often vertical fire barriers are used, which are also referred to as cavity closers. Their function is to close the cavity at the corners to avoid accumulation of wind load.

Horizontal cavity barriers are often designed in such a way that they allow the airflow behind a ventilated façade in normal use and block the cavity when exposed to fire. For this either intumescent barriers or metal elements are used.


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