Internal Fire Growth Once the fire takes hold within a building, the surfaces of walls and ceilings will contribute to the fire if they are ignited. Ensuring that these surfaces are non-combustible or, as a minimum, difficult to ignite means that, if a fire does start, its rate of growth or spread will be reduced. It is also desirable to keep to a minimum the amount of smoke or toxic fumes given off from this type of surface if involved in a fire, particularly those lining escape routes. The building may have fixtures, fittings, and contents such as carpets, curtains, etc. that are made from carbonaceous material or plastics that will quite easily burn and help in fire growth unless they have been treated to be flame-retardant. Fire-resisting walls, floors and ceilings which form escape routes will need to have fire resistance measures in place. Floors and walls should be fire-resistant to prevent the spread of fire and heat. Materials to help in this include the use of fire-resistant materials such as brick, concrete, ceramic tiles, and fire- resistant glazing. Ceilings should be made from materials that provide a negligible contribution to developing the fire and smoke and will not collapse during the early stage of the fire. The following are some of the materials and methods used to line room surfaces. Building Boards and Slabs Board materials all contain some fire resistance qualities but those with low performance qualities can be improved upon. Bonding, impregnating or other agents, including fire-retardants, may be added either during or after manufacture to modify particular properties. It should be noted that even though the face or surface of certain building boards may have good fire propagation properties the filling inside the board may decompose from the excess heat and some could give off flammable gases and create a flashover. An example of such a board filling would be polyurethane materials. Fibre building boards are manufactured in a wide range of sheet materials and are made from actual wood fibres. They derive their basic strength and cohesion from the felting together of the fibres themselves and from their inherent adhesive properties. Building boards of this group are not easily ignitable but typically are combustible. Plasterboards for interior use are composed of a core of set gypsum firmly bonded to two sheets of heavy paper to increase their tensile strength. In a fire, the exposed paper face may burn away making it relatively easy to break up the non-combustible gypsum core, but until this happens, the plasterboard will retard the spread of fire. Wall Linings Wall linings should also have fire resistance properties and should not easily ignite. Insulating properties of certain wall lining materials can, in fire conditions, increase the temperature in the area and help the spread or development of a fire. Over Painting Several layers of paint can easily make non-combustible surfaces become dangerous by increasing the potential for it to burn and spread a fire quickly. Walls and ceilings that started off with resistant materials could be painted with several layers of highly flammable paint and so reducing the surface to a dangerous level.
©SHEilds – All rights reserved FC V 5 JUN 2021
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