covering to improve weather resistance or the aesthetic appeal of the panel. The central core can be made of various insulating materials, ranging from virtually non-combustible through to highly combustible. However, problems can arise from having panels in place, such as the provision of hidden fire spread within the panels and the production of black toxic smoke. Fire spread could also lead to a flashover. Construction materials The materials used within the building will influence the speed and outcome of fire growth and fire spread. Some materials will have a good fire resistance level, and others will be highly combustible. Typical materials include: • Bricks are widely used in the construction of buildings and offer a good fire resistance level. • Concrete. This has good fire resistance and is more effective when used in block form. • Timber is combustible, but its resistance can be improved by treating it with fire retardant products. • Paints are used quite frequently on walls, ceilings, and other surfaces to slow the spread of fire. Flame-retardant and intumescent paints have been successfully manufactured which can now be applied to most surfaces. • Plastering is widely used on internal walls, and if the plaster consists of lathing or expanded metal, it can have a strong fire resistance level. • Plastics should be treated with fire retardants or protected in other ways. Failure to do this can aid in the spread of fire and the production of smoke. Internal linings Fire spread can be affected by the internal linings of the building, especially along the escape route. Internal linings of the building, such as walls, ceilings and partitions should be treated with a lining material which will restrict flame spread. The effect of ventilation Ventilation is the key factor in fire growth. If a fire has unlimited ventilation or air supply, then a flashover can easily occur. Ventilation systems will contribute to fire spread in two ways. Firstly, a ventilation system can provide a supply of fresh air (oxygen) to feed a fire and secondly, smoke (which is a fuel) can cause fire to spread through ventilation systems to other parts of the building, and bypass fire and smoke-resistant structures. The effects of contents During a fire, the contents of a building have an obvious effect on the rate of growth, and it is easy to imagine the dangers of a warehouse or enclosure containing (highly) flammable substances. However, it is well-publicised how rapid the rate of fire growth can be in a domestic house fire. Domestic fires, almost by definition, will influence items of furniture. The classic scenario of this is the materials of a sofa which when ignited can generate substantial heat (and smoke), due to the three methods of transmission, then ignite other items rapidly and increase the growth of fire throughout the building. A UK HSE guidance document HSG 64 ’Assessment of Fire Hazards from Solid Materials’ (now withdrawn) gave the following as examples of materials which were categorised as ‘high-risk’ and therefore present a great danger: • Acrylic fibre. • Acrylic mixture.
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