The German standard DIN 4102-1, Fire Behaviour of Building Materials and Elements - Classification of Building Materials - Requirements and Testing, has a long history and is widely used.
DIN 4102-1 classifies products into five fire performance classes: A1, A2, B1, B2, and B3. A1 and A2 are non-combustible classes; B1 is flame-retardant; B2 is combustible; and B3 is easily flammable.
Class A1
A1 materials contain no combustible components, produce no smoke, and generate no flaming droplets.
The specimen is placed vertically in an electric furnace at 750°C, while an additional 20 mm flame is applied. The test duration is 15–30 minutes.
A specimen is considered to meet Class A1 requirements if it satisfies the following conditions:
No visible flaming, subject to separate provisions for visible flame requirements.
Temperature rise inside the furnace is less than 50°C.
The material already satisfies the requirements for Class A2.
Class A2
A2 materials may contain a certain proportion of combustible components, but they produce no smoke and no flaming droplets.
Class A2 is the high fire performance class immediately below A1 and must pass a combination of tests. Some previous articles may have described only one method based on the actual testing practice of a specific laboratory. In fact, A2 classification has multiple testing paths.
Path 1 One of the Following Two Options
a. Furnace test
This test is the same as the A1 test, but the acceptance criteria are slightly less strict:
Flaming is allowed, provided the accumulated duration does not exceed 20 seconds.
The flame must not extend out of the heating tube, and the pilot flame height must not exceed 100 mm.
The temperature rise limit is the same as Class A1, namely ≤ 50°C.
b. Net calorific value and heat release tests
Both of the following tests must be passed:
Net calorific value test:
This test is performed using an oxygen bomb calorimeter. The prepared specimen is completely burned in a high-pressure pure oxygen environment, and the released heat is measured. The net calorific value Hu must be ≤ 4,200 kW·s/kg.
Heat release test:
This test uses a small test furnace conforming to DIN 4102-8. The combustion chamber is heated as required for 30 minutes. Immediately after fire exposure ends, a specimen of approximately 100 cm² is cut from the center of the test sample, with the same thickness as the original sample. The heat release per unit area is calculated based on mass loss per unit area and net calorific value. The heat release per unit area must be ≤ 16,800 kW·s/m².
Path 2 Mandatory
A Brandschacht, or vertical shaft furnace, test is conducted according to DIN 4102-15 and DIN 4102-16 to evaluate the flame spread performance of the material.
Specimens of specified dimensions are placed vertically above a burner and exposed to a prescribed flame impact for a certain period of time. Flame spread, flaming droplets, and residual length after combustion are observed.
Acceptance criteria:
The average residual length, meaning the unburned or charred remaining portion, of each specimen shall be ≥ 35 cm, and each individual value shall be ≥ 20 cm.
The average exhaust gas temperature shall not exceed 125°C.
No flame shall appear on the back side of the specimen.
No other abnormal events shall occur. Even if afterflame or afterglow/smouldering occurs, the residual length must still meet the minimum limit. The flame must not spread to the top surface of the sample, and no molten dripping shall occur.
Path 3 Mandatory
A smoke generation test is conducted to evaluate the toxicity of smoke produced by the material under decomposition and flame exposure.
The specimen is placed in a specified test chamber. Under heating or flame exposure conditions, the optical density, or absorbance, of the generated smoke is measured.
Acceptance criteria:
At any smouldering temperature, the measured average absorbance shall be ≤ 30%.
Under conditions without air supply, the measured maximum average absorbance shall be ≤ 15%.
In addition, DIN 4102-1 also specifies requirements for smoke density and smoke toxicity. For Class A materials involving smoke density and smoke toxicity, smoke density is tested according to ASTM D2843, the XP2 smoke chamber, and DIN E 53436/37. Toxic thermal decomposition products are determined according to DIN 53436 Parts 1–3. Latent heat is determined according to DIN 51900-2, and heat release is determined according to DIN 4102-8C.
Class B1
The requirements for Class B1 under DIN 4102-1 are also relatively complex. Taking curtain fabric as an example, the B1 test is as follows.
Class B1 uses the Brandschacht method. The test method is the same as the Brandschacht method used for A2.
Acceptance criteria:
The average residual length shall be not less than 150 mm.
The residual length of any individual specimen shall not be 0.
The average smoke gas temperature shall not exceed 200°C.
Even if afterflame or afterglow/smouldering occurs, the residual length must still meet the minimum limit.
The material must also pass the B2 test. In other words, to test for B1 classification, the material must first pass B2.
Class B2
Class B2 uses the small burner test.
For homogeneous materials, either edge ignition or surface ignition may be used. The flame height is 20 mm, ignition is applied at a 45-degree angle, flame application time is 15 seconds, and the test duration is 20 seconds.
Within 20 seconds, if the flame tip does not reach the specified mark, the material passes the test. If the edge is protected, an additional surface ignition test must be performed. If molten droplets ignite the filter paper below, the specimen fails. For non-homogeneous materials, specimens must be provided in both longitudinal and transverse directions for separate testing.
According to the requirements of DIN 4102-1, floor coverings classified as B1 must pass DIN 4102-14, with a critical radiant intensity of ≥ 0.45 W/cm² and a light attenuation integral of ≤ 750%·min, while also meeting the requirements of Class B2.
It can be seen that DIN 4102-1 is highly complex and detailed. To test for Class A2, the material must pass the B1 test and other tests. To test for Class B1, the material must pass both the B2 small burner test and the B1 Brandschacht test.
This is not a classification that can be determined simply by saying that a material does not ignite when exposed to a flame gun. Whether a material is non-combustible or not must still be evaluated through testing according to the standard.
