Cigarette lighting in the presence of oxygen-enriched atmospheres, such as one created by using oxy- acetylene welding and cutting equipment can cause many accidents. It is therefore impossible to over- emphasise the danger of smoking in oxygen-enriched atmospheres, or where oxygen enrichment can occur. In such areas, smoking must be forbidden and consideration given to prohibiting the carrying of smoking materials. The second factor is the speed at which flammable vapours are released from the fuels present. This will depend on the type of material, its size and the temperature it is being exposed to. Some materials, such as flammable liquids will readily give off vapours, and will significantly increase the amount of vapours given off as the temperature is raised by a small amount. Other materials, such as a large block of wood, may not readily give off vapours until exposed to particularly high temperatures. The size of the flammable material is significant, in that if it is small and finely divided, such as a dust or droplet of fuel, the rate of vapour being evolved and fire growth will be very rapid and may resemble an explosion.
The fire growth rate is mainly affected by the rate of production of flammable fuel in the form of vapours, and the availability of oxygen, but the following can also have an influence: • Smoke Movement. • Building Construction. • Ventilation. • Contents. Smoke movement This will be dictated by the temperature of the smoke. Cold smoke will spread laterally, possibly at a low level, presenting a principal hazard of reduced visibility, whereas hot smoke is more hazardous since it is a fuel above its ignition temperature and will spontaneously combust when it reaches available oxygen.
©SHEilds – All rights reserved FCV5 JUN 2021
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