What are the contents of BS476 fire resistance test standard for building materials?

Building materials play an important role in the fire prevention measures of buildings, so each country has strict corresponding requirements for the flame retardancy of building materials. Among them, the building material fire test standard BS 476 is also one of the important test standards, so what are its requirements for building material fire resistance?

BS 476-7 Fire test on building materials and structures－standard name: BS 476-7: Part 7: Method of test to determine the classification of the surface spread of flame of products. BS 476-7 is used for measuring the lateral spread of flame along the surface of a specimen of a product oriented in the vertical position under opposed flow conditions. BS 476-7 is primarily used for the determination of flame spread on exposed surfaces of walls and suspended ceilings.

BS476-7 Fire tests on building materials and structures - Standard application scope:

✓ Exposed surfaces of wall coverings

✓ Insulation exposed surfaces

✓ Exposed surfaces of ceiling materials

BS 476-7 Building materials fire resistance test - standard analysis:

BS 476-6 is used to compare the contribution of various materials of building materials to the formation of fire, and is mainly used to assess the fire performance of building materials and structures for wall and ceiling linings. The results of the determination are expressed in terms of flame spread index. Its test apparatus is shown in the figure below

The ignition source of this method is 2 electric heaters and 1 tube blowtorch. A chimney is installed on the burning tube of the building material flame retardant and fireproof test equipment, and a thermocouple is installed in the chimney to measure the flue gas temperature. The power of the electric heater is adjustable, and it is 45mm away from the vertically placed sample. The tube diameter of the tube blowtorch is 9mm, and there are 14 nozzles. The inner diameter of the nozzles is 1.5mm, and the center-to-center distance between each two nozzles is 12.5mm. The torch flame is applied at a point 25 mm above the bottom of the exposed surface of the test piece.

To evaluate the flame propagation properties of the tested material, the difference between the temperature in the chimney and the room temperature is continuously recorded with a thermocouple. And compare the obtained result (the relationship curve of temperature difference and time) with the calibration curve to calculate the value of the flame spread index i: the higher the I value of the building material, the lower the flame retardancy of the building material.

This test method for fire resistance of building materials and building structures is used to determine the propagation of flame along the surface of vertical plate test pieces. The measured results are suitable for comparing the fire performance of exposed surfaces of walls or ceilings. In this method, the sample is also ignited in the burning chamber, and the ignition source is a gas radiant panel and a medium-sized gas torch. According to the test results, the tested materials were divided into 4 grades according to the table. Class 4 materials have a high fire hazard and are not allowed to be used as building materials.