Fire behaviour

The term "fire behaviour" refers to classifications that describe the behaviour of substances and materials when exposed to fire.
The fire behaviour is divided into different classes of building materials. These include non-flammable materials, which are designated A1 and A2, and flammable building materials. These are B1, B2 and B3, which refer to flame-retardant, normally flammable and highly flammable materials respectively. In Germany, the classes of building materials are regulated by DIN 4102-1 . A newer classification system is the EU standard EN 13501. In Germany, there are five different classes of building materials, from A1-B3.

Building material classes A1 and A2 are characteristic of non- flammable materials, while building material class B includes flammable building materials.
The classification of the building materials is based either on the labelling of the substance or its packaging. Class A1 building materials are exempt from the labelling requirement, as are wood and wood-based materials that meet certain criteria (a gross density of at least 400 kg/m³ and a thickness of at least 2 mm).
The classification of building materials is verified by a test certificate, a test certificate with a test mark and the classification in DIN 4102-4 Fire behaviour of building materials and components. Coating the surface of a building material, for example, can change the proven fire behaviour. Therefore, the test marks for classes A and B1 indicate for which building material or composite the test was carried out.

Class A1

Class A1 building materials are non-flammable materials such as sand, gravel, clay, loam, stone, minerals, cement, gypsum, concrete, glass and metals.

Class A2 building materials

Class A2 building materials do not ignite spontaneously, but they do contain small amounts of combustible components. These include plasterboard and gypsum fibreboard, for example.

Class B1 building materials

B1 building materials are generally combustible, but must not continue to burn after the fire source has been extinguished. The materials of building material class B1 are flame retardant according to 1402-1.
Class B1 building materials include wood-wool building boards, gypsum plasterboard, pvc floor coverings (DIN 16951), oak parquet flooring and external thermal insulation systems.

Class B2 building materials

B2 materials can be ignited by sources of ignition and continue to burn independently depending on various conditions. B2 materials include wood and wood-based materials (unless they are classified as B1), PVC floor coverings (DIN 16951), linoleum coverings, electrical cables or textile floor coverings.

Class B3 materials

Class B3 building materials are combustible materials that can be ignited by even small ignition sources and continue to burn at an increasing rate without the addition of heat. B3 materials pose a high fire risk and may not be used in the construction or alteration of buildings, with a few exceptions . Materials that cannot be classified in any other building material class are considered highly flammable.