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Reaction to fire: how are construction materials classified?

30 November 2020
Article by Anabela Martins, technical manager of the Smoke and Fire Laboratory, and Edite Vale, responsible for Environment and Fire Services at INEGI.


Fire prevention in buildings does not begin with safety signs, smoke alarms and fire extinguishers, but with the construction of the buildings themselves. Minimizing the consequences of fires and associated fatalities depends to a large extent on the fire reaction behavior of the materials used in their construction or rehabilitation.

The ease and speed with which the materials succumb to flames, and the emission of toxic gases during a fire, are factors that can compromise the successful evacuation of the building's occupants.

The performance of fire reaction tests and the respective classification of materials is, therefore, an important requirement to be fulfilled by manufacturers. As required by law, these tests prove the performance of products when subjected to a fire.

Classification of construction materials is regulated at European level

The classification of reaction to fire for construction products, including products incorporated in construction elements, is defined in the EN 13501-1: 2018 . Also known as «Euroclasses», this standard provides for seven classes of reaction to fire for materials (A1, A2, B, C, D, E and F) with A1 being the class to which the materials that least contribute to the development of fire belong. and F the class of those with the greatest contribution.

This scale, using common technical terms, allows professionals, public authorities and consumers to be able to assess the performance of construction products, and to compare products from different manufacturers, in different countries of the European Union.

This classification is attributed based on data from a combination of tests, which simulate different fire scenarios to which the materials may be subjected in their actual use. The tests consider the extent of the damage produced, the spread of the flame, the release of heat, the production of smoke and the fall of particles, or flamed drops.

The tests become more demanding as you move up the rating scale. Class F - product in which fire performance is not determined, or which cannot be classified in any of the higher classes - Class A1 - products that do not contribute, or at least not significantly, to a fire , regardless of their end use.

Tests are carried out at INEGI's Smoke and Fire Laboratory

INEGI's Smoke and Fire Laboratory performs several of these tests on materials used in civil construction, namely:

Ignitability test
Evaluates the ignition phase of a fire and the flammability of a product exposed to a small flame. It is one of the necessary tests for classification in classes B, C, D and E.

Isolated combustion element test
Usually known as SBI (Single Burning Item), it evaluates the potential contribution of a product to the development of a fire, in a fire situation, simulating an isolated element in flames in a corner of a room close to the product in question. This test is relevant for classes A2, B, C and D.

Non-combustibility test and Upper calorific value test (PCS)
They represent the stage of a fully developed fire and are relevant to classes A1 and A2.

According to the Euroclasses system, there are also additional classifications for the production of smoke (s1, s2 and s3 - obtained from the SBI test) and for the fall of particles, or inflamed drops (d0, d1 - from the test on SBI and d2 - as a conclusion to the ignitability and SBI tests).