Technical Information – Fire
Behaviour In A Fire
Establishing the behavior of metal panels insulated with extruded polyurethane in a fire has always been difficult.
Additionally, the complexities of the various National Standards do not the help matters. This applies particularly to the “Reaction to the fire” and “Resistance to fire” concepts, which define the behaviour of materials.
Reaction To Fire
Reaction to fire is the degree to which a material resists combustion. With regard to this, materials are assigned a class (0, 1, 2, 3, 4, 5): the higher the class, the higher the degree of combustion.
The fire reaction class is established through tests of small sized samples, which are carried out by following extremely strict standards, which vary from country to country. For this reason, except for Class 0, which is an ISO standard, it is difficult to make any correlation between the classifications accepted by the various national standards.
The non-combustibility test to assign Class 0 is carried out to the ISO-DIS 1182.2 standard, which envisages to a very small sample material to 750 C and checking the following parameters:
- Formation of flames
- Increase in temperature
- Loss of weight
In Italy, when the material passes this test, it is assigned Class 0, which in Germany is called A1 and in France MO.
No organic substances achieve Class 0, so they must be classified with other methods. For the Italian laws, they are:
- CSE RF 1/75/A – Suspended materials attacked by flames on both sides
- CSE RF 2/75A – Materials attacked by flames on one side
- CSE RF 3/75A – Materials subject to one flame and radiant heating
- Methods CSE RF 1/75A or CSE RF 2/75A are used according to the type of material.
- The Fire Reaction Class of the product is established by combining these categories.
The other European countries classify the fire reaction in a different way, and particularly:
B1 – B2 or B3 (DIN 4102)
The material is tested with a small flame (B2) and in a furnace as the walls of a fireplace. If it doesn’t pass the B2 test, the last class B3 is automatically assigned.
from M1 to M5 (ANFORM NFP 92-501)
The test is carried out by means of an “Epiradiateur”, with the same attendance presence flames and head supplied by a radiating surface. The M1 class is the best one, for organic material while the M5 is the worst.
Ref: Ministerial Decree of 26.06.84 – Fire reaction classification and approval of materials for fire prevention purposes.
Resistance To Fire
The resistance to fire is the ability of the building material to keep its mechanical stability, not to spread flames, or to have a thermal insulation for a certain period of time. The resistance to fire is expressed as the time, in minutes, from the beginning of the heating period until the tested component ceases to comply with the requirements that it must meet. The fire resistance test is carried out by following the instructions of Circular no. 91 of the Ministry of the Interior (1961), which requires the installation of a portion of wall (or floor) at the hole of a furnace. The furnace is heated following a well-defined temperature scale, and some parameters are controlled that help identify the fire resistance class of the material.
The following aspects are controlled:
- Mechanical stability
- Resistance to flames, fumes and exhausts
- Thermal insulation (symbol : R)(Symbol : E) (symbol : l)
The building material can have a variable fire resistance level, resulting from the combination of the REI, RE, R requirements.