material. They should be correctly stored and away from ignition sources. Where possible flammable materials should be used instead of highly flammable materials.
Flammable limits The following are definitions of the Lower Flammable Limit (LFL) and the Upper Flammable Limit (UFL): • The LFL is the minimum concentration of flammable liquid vapour in air that will support the propagation of flame or spread of flame through the entire volume of vapour-air mixture, upon contact with an ignition source. • The UFL is the maximum concentration of vapour in air that will support the propagation of flame. The proportion of vapour to air mixture that is ignitable is referred to as the flammable range and is expressed in terms of the percentage of vapour in air by volume. The flammable range is bound by the LFL and UFL . Later in this element, you will cover a section on 'Explosion'. You will find that flammable limits here are referred to as upper and lower explosive limits. The conditions required to cause the ignition of combustible solids, flammable liquids, and gaseous materials Ignition of combustible solids, flammable liquids and gaseous materials can occur if the conditions are ideal for the ignition to take place. This condition is when a heat source, such as a spark contains sufficient heat energy to cause combustion of one or more molecules of a flammable vapour or substance. As well as the heat source, fuel and oxygen must also be present (as previously discussed in an earlier lesson). The concentration of the vapour in the air must be between the flammable limits for the ignition to be successful and there must be the correct mix of flammable vapours, dusts, or gases with air in the right ratio. The flammable limit and the level of the ignition energy will vary depending on the type and form of the fuel. E2.2 Summary In this section we have covered: The ignition of solids, liquids, and gases
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