Certification and Registration
British Building Materials Flame-Retardant Standards BS 476-7 and BS 476-6
Category:
European
As a fundamental component of daily life, building safety has always been a major concern. While traditional building materials can ensure structural integrity and stability, they often have limitations in terms of aesthetic requirements. With the development of new technologies and materials, an increasing number of innovative materials are being used in building façades and interior structures. For example, various exterior building materials, LED billboards, and flight or train information display systems installed in airports and high-speed railway stations are now widely used. While these materials provide convenience, they may also introduce certain fire hazards.
Each country has established regulations governing the flame-retardant performance of construction materials. These regulations impose strict requirements on the fire performance of building materials and products to ensure occupant safety. When building materials or products involved in fire incidents are found to contribute to casualties, regulations are updated with additional requirements and testing methods to address the related issues.
The requirements for construction materials in the United Kingdom are specified in relevant regulations. According to these regulations, fire performance testing of materials is conducted in accordance with the BS 476 series of standards. In addition, countries and regions such as Singapore, certain European countries, Hong Kong, and Macao also recognize and adopt UK flame-retardant standards. Therefore, the BS 476 series has become one of the important testing standards for construction materials in international trade.
The BS 476 series consists of multiple standards. Commonly used tests for construction materials include:
BS 476-3 Fire tests on building materials and structures — Part 3: Classification and method of test for external fire exposure to roofs
BS 476-4 Fire tests on building materials and structures - Non-combustibility test for materials
BS 476-6:1989+A1:2009 Fire tests on building materials and structures-Method of test for fire propagation for products
BS 476-7 Fire tests on building materials and structures-Surface spread of flame tests for materials
BS 476-8 Fire tests on building materials and structures-Test methods and criteria for the fire resistance of elements of building construction
BS 476-11Fire tests on building materials and structures - Method for assessing the heat emission from building materials
BS 476-12 Fire tests on building materials and structures - Method of test for ignitability of products by direct flame impingement
BS 476-20 Fire tests on building materials and structures - Method for determination of the fire resistance of elements of construction (general principles)
BS 476-21 Fire Testing of Building Materials and Components - Test Method for Fire Resistance of Load-Bearing Components
BS 476-22 Fire tests on building materials and structures - Methods for determination of the fire resistance of non-loadbearing elements of construction
BS 476-23 Fire tests on building materials and structures - Methods for determination of the contribution of components to the fire resistance of a structure
BS 476-24 Fire tests on building materials and structures. Method for determination of the fire resistance of ventilation ducts
BS 476-31.1 Fire tests on building materials and structures - Methods for measuring smoke penetration through doorsets and shutter assemblies - Method of measurement under ambient temperature conditions
For insulation materials exported to the UK, LED display materials, wall panels, ceiling tiles, and other building products shall comply with British standards. Surface flame spread testing shall be conducted according to BS 476-7 and/or BS 476-6. If the product is required to achieve Class 0, both BS 476-7 and BS 476-6 tests shall be conducted.
According to Approved Document B (Fire Safety) of the UK Building Regulations, outdoor structures exceeding certain heights or buildings with higher fire risks are required to use Class 0 materials to reduce or prevent fire occurrence.
Class 0 (Level Zero) is widely recognized in developed countries as one of the safest classifications for rubber and plastic foam insulation materials. In the UK and regions such as Singapore and Hong Kong, insulation materials used in central air-conditioning systems are required to meet Class 0 requirements. In addition, many factories and office buildings in China also require the use of high-performance insulation materials meeting Class 0 requirements to improve safety and product quality.
According to Appendix A13 of Approved Document B of the UK Building Regulations, the assessment of Class 0 shall be based only on test results from BS 476-7 and BS 476-6.Class 0 materials shall meet the following two requirements:
1) According to BS 476-7 Testing, the product meets Class I ; and
2) According to BS 476-6 Test, total flame spread index of the product I≤12 , and the flame spread index i≤6
BS 476-7 Test Overview
BS 476-7:1997+AC:2014 (also referred to as BS 476 Part 7 or BS 476-7) specifies a test method for determining the lateral flame spread on the surface of vertically oriented specimens under radiant heat exposure conditions. It defines combustion classifications based on flame spread rate and flame spread distance. The standard is mainly used to evaluate the flame spread characteristics of exposed surfaces of wall panels and ceiling tiles.
The test method involves igniting the specimen inside a combustion chamber using a gas-fired radiant panel and a medium-sized gas burner as ignition sources. The radiant panel provides a heat flux of 32.5 kW/m² at a position 75 mm from the leading edge of the specimen. The burner flame height is 75–100 mm and is applied to the specimen in the same direction as the radiant panel. The specimen is exposed to the radiant heat source for 10 minutes, and the flame spread distance is recorded at 1.5 minutes and 10 minutes.
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BS 476-7 The testing process is as follows: |
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1. Heat the radiation panel until it reaches the specified radiation intensity. |
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2. Ignite the kindling flame |
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3. Install the specimen, including the backplate and other components, on the secondary position of the specimen holder. 5min Completed internally |
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4. Quickly rotate the sample holder to the test position and simultaneously start the timer to begin the test. |
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5. Test started 1min Then extinguish the ignition flame; observe the experimental phenomena. |
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6. Record the time when the flame front reaches the reference line and after the start of the test. 1.5min and 10min The distance of the flame front at that time |
BS 476-7 Test Level Classification
BS 476-7 divides materials into four classes. Class 1 represents the highest flame spread classification, while Class 4 represents the lowest classification and is generally not suitable for use in building materials. The classification is as follows:
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Grading |
In 1.5 Flame propagation at the minute mark |
Final Flame Propagation |
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Distance restriction /(mm) |
Limitation of a single specimen (mm) |
Distance restriction /(mm) |
Limitation of a single specimen (mm) |
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Class 1 |
165 |
165 + 25 |
165 |
165 + 25 |
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Class 2 |
215 |
215+25 |
455 |
455+25 |
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Class 3 |
265 |
265+25 |
710 |
710+25 |
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Class 4 |
More than Class 3 The limitation |
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BS 476-6 Test Overview
BS 476-6:1989+A1:2009 (also referred to as BS 476 Part 6 or BS 476-6) specifies a test method for assessing the fire propagation performance of products such as wall and ceiling materials by determining the flame spread index.
The ignition sources used in this method include two electric heaters and one tubular gas burner. The burner is equipped with a chimney on the combustion tube, containing a thermocouple for measuring flue gas temperature. The power of the electric heater is adjustable and positioned 45 mm away from the vertically mounted specimen.
The tubular burner has a tube diameter of 9 mm and contains 14 nozzles with an internal diameter of 1.5 mm and a center-to-center spacing of 12.5 mm. The burner flame is applied to the exposed surface of the specimen at a height of 25 mm above the base.
BS 476-6 Flame Spread Index Assessment
To evaluate the flame propagation performance of materials according to BS 476-6, the temperature difference between the flue gas and ambient temperature is continuously recorded using thermocouples. The recorded results are compared with a calibration curve obtained using asbestos-cement boards of specified density tested under the same conditions.
The temperature differences between the test specimen and calibration curve are determined according to the following criteria:
1) During the first 3 minutes of the test, temperature difference values are recorded every 30 seconds.
2) During 4–10 minutes, temperature difference values are recorded every 1 minute.
3) During 11–20 minutes, temperature difference values are recorded every 2 minutes.
The flame propagation index i for each of the three periods is calculated separately according to the specified formula.
The total flame spread index I is the sum of the three flame propagation indices:
I=i₁+i₂+i₃
The higher the value of I, the lower the flame-retardant performance of the material.
SATISFY has a professional flame-retardancy testing team and testing capabilities compliant with European, British, American, Chinese, Australian, and other national and regional standards. We provide end-to-end flame-retardancy testing services, including test consulting, standard interpretation, sample testing, report analysis, and product optimization.
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