“National Class” is the rating achieved after testing to the BS476 test. There are many aspects and parts to this test, but the two that we as coatings suppliers are concerned with are as follows:
BS 476 part 6: Fire Propagation Test.
This measures the amount of heat released when the product under test is burned. This is essentially a pass/fail test.
BS 476 part 7: Surface Spread of Flame Test.
The test produces a fire rating of Class 1, 2, 3 or 4 depending upon how far a flame travels over a coated surface. Class 1 is the best rating i.e. the lowest flame spread.
To achieve Class 0 a product must achieve Class 1 in the Part 7 test and also pass the Part 6 test.
Fire Upgrading Coating Systems.
A “Fire Upgrading” Coating System is one that has been tested on the Warrington Class 4 “Blue Board” and upgrades the fire rating.
- A Class 1 Fire Upgrading System will reduce the “Blue Board” surface spread of flame to Class 1.
- A Class 0 Fire Upgrading System will reduce the “Blue Board” surface spread of flame to Class 1 and significantly reduce the amount of heat released.
The Warrington Blue Board has become the standard test substrate upon which all fire-upgrading coating systems are tested. The board is a multi layer painted test substrate used for assessing the performance of fire upgrading coating systems to simulating real life scenarios where surfaces may have had numerous redecoration’s. When ignited, it is designed to illustrate a worst case scenario in terms of combustibility and rapid spread of flame. The test gives specifiers a known performance level for measuring a coating systems fire performance claims.