Fire spread, principles

The basic fire prevention principle in all buildings is to divide up the buildings into compartments with effective fire and heat insulation so that a fire in any one compartment is prevented from spreading to others. This principle also applies to shafts, ducts and false ceilings all of which should have effective fire and smoke barriers built into them at suitable intervals. 

Fire prevention training courses include the causes of fire and fire spread, fire and smoke alarm systems, emergency lighting, the selection and use of fire extinguishers and sprinkler systems, evacuation procedures, high risk operations and good housekeeping principles. 

By using heat detection devices operating on the rate-of-rise or fixed-temperature principle, or other devices such as ultraviolet or infrared detectors designed for individual hazards, it is possible to apply water to a fire more quickly than with systems in which operation depends on opening of sprinklers only as the fire spreads. 

For textile materials used as interior wall-coverings in U.K. buildings including railway carriages, where the fabric could be in a vertical orientation attached to the wall panel, measurement of rate of flame spread under external heat flux is one of the requirements. For such applications, the test method (BS 476 Part 7) essentially requires a vertically oriented specimen exposed to gas-fired radiant panel with incident heat flux of 32.5kW/m2 for lOmin. In addition, a pilot flame is applied at the bottom corner of the specimen for 1 min 30 s and rate of flame spread is measured. The same principle is used in the French test for carpets, NF P 92-506. 

In normal atmospheric conditions, fire is initiated by a combustible material coming into contact with a heat source. The spread of fire occurs due to direct flame impingement of the transfer of heat to the surrounding combustible materials. Heat transfer occurs by three principle mechanisms—conduction, convection, and radiation. Conduction is the movement of heat through a stationary medium, such as sohds, liquids, or gases. Steel is a good conductor of heat as is aluminum, therefore they can pass the heat of fire if left unprotected. 

These distances will depend on the dimensions of the aircraft involved in the assumed crash and the characteristics of the assumed flight path. As a minimum, the distances should be sufficient to prevent the aircraft impact from reducing the system s capability to perform the safety functions below acceptable levels, for example by redundancy. Intermediate barriers between initial impact surfaces and the systems and components required to perform functions should be evaluated. The combination of the principles of separation, segregation and diversity can help to ensure the performance of SSCs. The spread of fire, in an area much larger than the impact area, caused by burning spilled fuel and burning debris should also be considered in relation to this concern. 

An understanding of the principles are critical to identifying how a fire will start and spread, the former of which are known as primary fire hazards, each of which has the ability to initiate or start a fire, or exacerbate a fire. These elements will be required when completing a fire risk assessment. 

Approved Document B of the Building Regulations classifies performance of internal linings. These will be discussed in future chapters however, the principles involve ensuring that the internal linings should adequately resist the spread of fire over their surfaces and, if ignited, a rate of heat release which should be reasonable in the circumstances. 

Flame retardant additives are added to the electrolyte to inhibit or delay the onset of radical propagation reaction and prevent the spread of fire when a thermal runaway occurs in a battery. Flame retardant additives have been widely used in other areas such as the plastics and coating industry, and battery flame retardant additives are designed with the same principle. However, more stringent requirements are applied to the battery additives, as the additives must be electrochemically inert, and preferably would have a positive effect on the battery performance. 

Nagy acknowledges that these reports are inadequate for his purposes. He wants detailed observations and technical principles he can use to draw conclusions about the Wilberg fire, but most reports do not give specific information on [such issues as] the effect of air velocity on flame spread. These reports take for granted that these effects are common knowledge and thus provide little help with the current case. ... 

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