European Standard provides the reaction to fire classification procedure for all construction products are covered by EN 13501-1. This document applies to three categories, which are treated separately in this document:

1. Construction products (tabel no.1),
2. linear pipe thermal insulation products – A1L, A2L, BL, CL, DL, EL and FL (table no.2).

Table no. 1 – Classes of reaction to fire performance for construction products excluding
floorings and linear pipe thermal insulation products.

A) – For homogeneous products and substantial components of non-homogenous products.
B) – For any external non-substantial component of non-homogenous products.
C) – Alternatively, any external non-substantial component having a PCS ≤ 2,0 MJ/m2, provided that the
products satisfies the following criteria of EN 13823: FIGRA ≤ 20 W/s and LFS < edge of specimen
and THR600s ≤ 4,0 MJ, and s1, and d0
D) – For any internal non-substantial component of non-homogeous products.
E) – For the product as a whole.
F)
– s1 = SMOGRA ≤ 30 m2/s2 and TSP600s ≤ 50 m2;
s2 = SMOGRA ≤ 180 m2/s2 and TSP600s ≤ 200 m2;
s3 = not s1 or s2
G)
– d0 = No flaming droplets / particles in EN 13823, within 600 s;
d1 = No flaming droplets / particles persisting longer than 10 s in EN 13823, within 600 s;
d2 = not d0 or d1;
(Ignition of the paper in EN ISO 11925-2 results in a d2 classification)
H) – Pass = no ignition of the paper (no classification);
Fail = ignition of the paper (d2 classification)
I) – Under conditions of surface flame attack and, if appropriate to the end-use application of the product,
edge flame attack.

…

Table no. 2 – Classes of reaction to fire performance for linear pipe thermal insulation products

A) – For homogeneous products and substantial components of non-homogenous products.
B) – For any external non-substantial component of non-homogenous products.
C) – For any internal non-substantial component of non-homogenous products.
D) – For the product as a whole.
E)
– s1 = SMOGRA ≤ 105 m2/s2 and TSP600s ≤ 250 m2;
s2 = SMOGRA ≤ 580 m2/s2 and TSP600s ≤ 1 600 m2;
s3 = not s1 or s2
F)
– d0 = No flaming droplets/ particles in EN 13823 within 600 s;
d1 = No flaming droplets/ particles persisting longer than 10 s, in EN 13823, within 600 s;
d2 = not d0 or d1;
Ignition of the paper in EN ISO 11925-2 results in a d2 classification.
G) – Pass = no ignition of the paper (no classification);
Fail = ignition of the paper (d2 no classification)
H) – Under conditions of surface flame attack and, if appropriate to the and use application of the product,
edge flame attack.

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According to the SBI method, the test involves subjecting a corner-shaped sample with dimensions of height 1500mm and wing lengths: short (500mm) and long (1000mm), exposed to the 32.4 kW fire flame of a sand burner.

View of the testing facility

Description of the testing facility

The detailed construction of the equipment is described in the EN 13823 standard. The SBI equipment consists of three main sections: the testing chamber, the measurement trolley, and the flue gas analysis section.

The testing chamber is constructed using fire-resistant materials and has internal dimensions of 3x3m and a height of 2.4m. It has an entrance for the operator and allows for walking on the roof, where the flue gas analysis section is located. The sand burner, identical to the one on the measurement trolley, is installed in the chamber. It serves as the background burner, and its role is described further in the text.

The measurement trolley is built on a mobile, steel frame. The sample and bottom plates, used for creating the so-called “air gap,” are installed on the measurement trolley. The methods of sample installation are described in a separate article.

The flue gas analysis section is the most complex part of the testing setup. It includes temperature sensors, an analyser for measuring the O₂ and CO₂ content in the flue gases, a pressure difference sensor for measuring the velocity of the flue gases, a fan with adjustable performance, and a system for measuring light beam attenuation.

Testing Procedure

To conduct the test, the material sample is placed on the measurement trolley.

View of the sample ready for testing.

A sand burner that generates a 32.4 kW fire flame during the measurement procedure, is located in the lower corner of the sample.

After introducing the sample into the testing chamber, the actual measurement procedure begins, consisting of the following stages:

1. Environmental conditions measurement – the standard precisely describes the required conditions for the test. If they are not met, the measurement has to be suspended.
2. Initial conditions measurement – during this stage, the system reads and calculates the averages of parameters such as O₂ and CO₂ content, ambient temperature, air temperature in the measurement channel, humidity, pressure, and light intensity over a period of 3 minutes.
3. Operation of the auxiliary burner – the auxiliary burner installed in the testing chamber operates for the next 3 minutes. During its operation, the burner power and the amount of generated smoke are recorded. The parameters calculated during this stage are described later in the article.
4. Main exposition of the sample to fire – the tested sample is exposed to fire for 20 minutes. During this stage, parameters necessary for the classification are measured, including THR (Total Heat Release), SPR (Smoke Production Rate), FIGRA (Fire Growth Rate), and SMOGRA (Smoke Growth Rate).
5. Waiting time for sample extinction – after the exposition, the sample in the testing chamber should extinguish completely and stop emitting heat and smoke. The standard allows for manual extinguishment of the sample by the operator.
6. Measurement of final conditions – after the sample has been extinguished, the parameters necessary for calculating the analyser drift and the light beam attenuation drift are measured.

Calculation of classification parameters:

THR_600s (Total Heat Release) – this parameter represents the total amount of heat released by the sample during the first 10 minutes (600 s) of exposition. It is calculated based on the sum of the parameter HRR(t).

FIGRA_0.2MJ – this parameter describes the heat release rate by the sample, measured when THR(t) > 0.2 MJ, meaning if the sample releases more heat than 0.2 MJ at a given moment.

FIGRA_0.4MJ – this parameter describes the heat release rate by the sample, measured when THR(t) > 0.4 MJ, meaning if the sample releases more heat than 0.4 MJ at a given moment.

TSP_600s – this parameter describes the total amount of smoke produced during the first 600 seconds of exposition. It is calculated based on the sum of the parameter SPR(t).

SMOGRA – the maximum smoke generation rate by the sample during the entire exposition.

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1. Humidity is measured in the range of 20-80% ± 5%.
2. Ambient temperature: the thermocouple is located near the exit of the measurement trolley, close to the floor.
3. Ambient pressure with an accuracy of ±200 Pa.
4. Light beam attenuation measurement system: it consists of a stabilizing structure, a light source with a colour temperature of 2900K ±100K, a lens system, and a detector.
5. O₂ level is measured by a paramagnetic analyser with a minimum resolution of 0.01%.
6. CO₂ level is measured by an infrared (IR) analyser with a minimum resolution of 0.01%.
7. Flue gas velocity: measurement is carried out using a bi-directional probe and a pressure transducer.
8. Flue gas temperature: measured by three thermocouples placed in the flue gas measurement pipe.

What parameters does the measurement system calculate at the SBI test, and what do they signify in relation to a real fire?

THR_600s – this parameter describes the total heat released by the sample during the first 600 seconds of the test. This parameter allows to estimate the impact a particular material will have on fire development. For example, it indicates whether igniting the material will cause the fire to spread to other materials or if the released energy is sufficient to initiate or sustain the combustion process.

FIGRA – this parameter describes the rate of heat release by the tested material. It allows to estimate how quickly the material will propagate fire. In combination with the THR parameter, it enables the estimation of the likelihood and speed of fire growth.

SMOGRA – this parameter describes the rate of smoke generation by the material involved in the fire. It is particularly important for public utility buildings, production halls, and warehouses. It allows the estimation of the time after which evacuation of a room will become impossible due to smoke.

TSP_600s – this parameter indicates the amount of smoke generated during the first 600 seconds of the test. It allows the estimation of whether the emitted smoke quantity during a fire will reduce visibility. This information is crucial for determining evacuation routes and hazard zones.

How are the individual parameters calculated?

The measurement system of the SBI test records the values of each measured parameter every 3 seconds throughout the entire measurement procedure. Subsequently, it calculates the primary parameters, namely:

HRR(t) – Heat Release Rate index, SPR(t) – Smoke Production Rate index.

To calculate the HRR index, the system calculates:

V298(t) – volumetric flow rate in the measurement pipe,

(t) – oxygen depletion coefficient,

x_{a_O2} – mole fraction of oxygen in the environment, including water vapor.

Based on the equation provided, the parameter HRR_total(t) is calculated.

Subsequently, thanks to the auxiliary burner’s operation, it is possible to calculate the parameter HRR of the burner itself (HRR_{av_burner}), which represents the average HRR_total during the period of 210-270 seconds of the test. By subtracting the HRR_{av_burner} from the total HRR during the sample burning, the HRR parameter specific to the sample can be obtained.

Based on the above calculation, the final parameter, THR_600s, is calculated using the formula:

Also, based on the HRR(t) parameter, the FIGRA is calculated. This parameter is divided into two ranges: 0.2 MJ, which means it is measured when the conditions HRR_av(t)>3 kW and THR(t)>0.2 MJ are met, and 0.4 MJ, which means the conditions HRR_av(t)>3 kW and THR(t)>0.4 MJ are met.

This parameter is measured during the entire exposition to the sample and is calculated using the formula as follows:

The next parameters calculated by the measurement system are TSP_600s and SMOGRA. Due to the fact that the density of smoke varies with temperature during the test, the first step in calculating the smoke parameters is to determine the velocity at which air flows in the measurement system. The following formula is used for this purpose, utilizing the volumetric flow rate (V298) calculated at a temperature of 298 K and the average temperature of smoke in the measurement pipe:

Next, the smoke production rate SPR_total(t) is calculated using the formula:

Similarly, to the HRR calculations, it is necessary to separate the smoke parameter SPR_total into two components: the smoke generated from the tested sample and by the burner itself. This separation is performed during the operation of the auxiliary burner and is expressed as the sum of the following terms:

Once we have obtained the parameter SPR(t), which represents the smoke generated by the sample alone, we can calculate the value for TSP_600s using the following equation:

Once we have obtained the parameter SPR(t), which represents the smoke generated by the sample alone, we can calculate the value for TSP_600s using the following equation:

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