Fire spread in trade building
Undeniably, the intensity of fire spread in buildings is significantly determined by fire behaviour, which involves but is not limited to stage of fire development, behaviour of fully developed fires inclusive of the temperature development, role of ventilation as well as duration. Moreover, burning behaviour of materials such as energy release rates and mass loss is another fire behaviour that influences spread of fires (Siu, 2008). Upon ignition of a material, fire spreads across it until it becomes completely involved. The rate at which the flame spreads are dependent on the combustion rate of the material, surface area exposed to the flame as well as availability of air.
Combustible materials usually initiate fires, at the initial stage of fire outbreak, which lead to production of smoke by the burning object. At this stage, control of fire outbreak is easier. Thereafter, smoke produced is transferred via the smoke plume, which then collects at the upper position of space as a layer. The smoke plume further transports heat produced by the by the fire into the smoke layer, which results in depth and temperature increase (Jinhua, & Guanquan, 2008). Radiation then occurs on the unburned materials thus resulting in temperature increase. Thereafter, fire is transferred through various modes of transmission inclusive of conduction, radiation as well as convection. The latter is the risky mode of transfer mode as it evidently leads to more deaths and casualties.
In the United Kingdom, there are buildings regulations that must adhered to by persons constructing buildings. The regulations aim at ensuring that the policies set out in the regulations are followed to the later. The regulations emphasise on five aspects aimed at ensuring fire safety in the construction of buildings. The aspects include;
-Means of escape; provision emphasises on designing of buildings in such a way that in case of fire outbreaks, occupants can escape to safer grounds on their own. This may necessitate the incorporation of fire alarms to warn occupants in case of fire incidences.
- Internal fire spread (linings); spread of fire through the inner linings should be minimised at all costs
-Internal fire spread; in order to ensure sustainability of buildings in the event of fire outbreaks, as well as ensuring that there is appropriate separation within\, and between adjourning buildings, there is a need for the provision of an automatic fire suppression mechanism where need be. This will also inhibit the spread of fire and smoke in concealed spaces of the buildings.
-External fire spread; external walls and roofing’s should provide adequate fire resistance mechanism. This will suppress the spread of fire from one building to the other
-Access and facilities for outstanding service; there should be adequate and satisfactory access to fire appliances to assist fire-fighters in saving lives of people in and around the buildings.
Deductively a fire spread in a building is because of various factors. These factors include internal linings in buildings, external walls as well as cavities found in the buildings.
Fire spread on internal linings
Materials used to make internal linings of buildings significantly contribute to the growth and spread of fire. This is mainly attributed to the spread of the flame across their surface. This is also due to the amount of heat released during combustion. The initial aim of designing internal linings in a building is to ensure that fire is contained within one room or space of origin. Internal linings should be designed in a way that prevents the spread of smoke and fire by resisting compartmentalization, in order to maintain structural integrity for a reasonable period. The materials used to design the internal linings of buildings substantially determine the rate of spread of fires. Linings of internal walls should be designed to prevent the spread of fire through the internal linings. Moreover, such internal linings can hinder escape of fire outbreak victims since they are round shaped.
Spread of fire in trade buildings
Trading facilities inclusive of trade buildings are designed and constructed to provide feasible fire resistance in case of any fire outbreak. This allows time to regain stability in case of fire outbreaks. As an example, fire outbreaks can result from an oxygen cylinder, which explodes in a side room resulting in the collapse of a ceiling and final spread of the fire to other rooms. Deductively trade buildings should be designed in such a way that it prevents smoke and fire from spreading to close buildings. The most probable reasons for the spread of the fire incidents at the trade buildings include the presence of doorways, which allow spread of fires from origin rooms to occupied areas. Although there are doors, which is fire resistant, fire can spread through them if the doors are held by fire debris, wedge or lack of doors closer (Marchant, 2000). To prevent such fire spreads these doors in compartments walls should have fire resistance performance, which should be the same as that of walls.
Incidences off fire spread also occur through non-loading partitions, walls as well as through unstopped ceiling voids. Moreover, fire spreads through stairways from one compartment to another. In such cases, fire spreads upwards if doors have direct openings with the staircase from the room of origin. In order to address such instances, stairways passing from one compartment to another should be enclosed in a “potential shaft”, which will ensure achievement of specified fire resistance performance. The protected shafts should be coated with glazed screens, between the stair and the lobby or corridor, thus, allowing achievement of high fire resistance.
In the initial stages of construction of laths and plasters on the ceilings, they sometimes fail to get fixed thus giving allowance for the spread of fire to other locations above trade building roofs due to damage on the ceiling materials. While carrying out maintenance and installation processes, ignition and combustible materials within the external walls are likely to allow fire to spread through cavities to upper floors and roofs. Finally, existence of furniture in trade buildings including curtains, may lead to ignition along the lower edges of beddings and bed covers, which could penetrate to a combustible lining of the ceiling.
Structural elements in a building
The major structures in a building mainly entail the floor, the load bearing wall, and the column/beam, which provide protection from early failure thus allowing for optimal fire resistance thus maintaining the building from collapsing as well as failure of the capacity of the load bearing. When designing a building, it is advisable to consider the resistance to fire penetration as well resistance to heat transfer. The mentioned is significant as it allows the ability to curb fire incidents as well as meeting the demanded consequences (Chandrakantan, 2004). The structures should meet fire resistance requirements over a standard period.
Spread of fire on External Walls
The UK Fire safety regulations classify the spread of fire on external walls under the fourth aspect B4. Under this safety rule, it is empathically crucial that trade buildings be spaced apart with sufficient space in order to provide enough openings on wall boundaries. The Communities and Local Government provide policy responsibility for fire safety in trade buildings and such policy regulations are covered under the Fire Safety Order 2005 (Pickard, 2004). To this purpose, owners of trade buildings are called upon to undertake a risk assessment in fire safety in their premises in addition to putting measures in place that cautions, protects, and upholds management of fire spreads (Chandrakantan, 2004; Jinhua, & Guanquan, 2008).
Spread of fires on external poses serious problems given that the fire is not only capable of spreading upwards or downwards the same building but also, the fire can spread to adjacent buildings. Equally, majority of current buildings are built with combustible exterior cladding materials thereby increasing the intensity of fire spread on external walls. Three different mechanisms are capable of contributing on the spread of fire on external walls.
Cracks at the junction of the wall and the exterior floor
Window to window causes a leapfrogging mechanism that ignites combustible materials on the window surface
Surface spread mechanism where fire is propagated upwards along the assembly of the exterior wall
Spread of Fire through Cavities
It is fundamental to limit the spread of fires through cavities by creating cavity barriers on trade buildings, in as well to installing fire resistance equipment on the edges of wall cavities. For instance, cavity barriers should be installed on the window and door openings, and roof spaces and cavity barriers should separate these cavities by allowing a maximum distance of no more than 20m. Cavity barriers are designed in a manner that inhibits the passage of flames and smoke in addition to providing insulation for the cold section of the wall from increasing the level of temperatures in case a fire erupts. In order to achieve fire resistance of the right intensity, it is necessary that compartment walls be constructed to their full heights on the compartment floors (Chow, and Chow, 2009). Last, these cavity barriers should be of the right quality such that temperature changes, shrinkage, and thermal collapses do not affect it. For buildings exceeding 18m, non-combustible building materials should be used to cover cavities on external addition.
Compartmentation
In trade buildings, fire compartmentation accounts for one of the most critical criteria for preventing the spread of fire and fire damages. As such, proper Compartmentation is capable of containing the fire to within the original starting point of the fire even at the toughest situations where other fire prevention mechanisms have failed (Marchant, 2000). The format of compartmentation delays the spread of fires depending on the structure of the compartmentation. Strong compartmentation should be capable of containing the spread of fires for at least 30 minutes while awaiting the arrival of the fire brigade. Horizontal evacuation and escape routes are necessary in every floor to at least provide enough space for evacuation in case of a fire outbreak (Marchant, 2000).
Construction of compartmentation
Several requirements must be fulfilled during the construction of compartmentation and these are specified under the national building codes. Among the major requirements, include the separation of exits, floors, and foremost occupancies. Other requirements include the separation of zone areas near floors, suites, and areas of refuge. The size of compartmentation is dependent upon the size of the building and the usage (Chandrakantan, 2004). Equally, cavities on walls should possess equal fire resistance capabilities in order to deliver equal strengths during prevention of fire outbreaks. Exits such as doors play a fundamental role in preventing and separating firetraps and hence, they should be located in significant places such that they act as safety routes for occupants, and fire fighters.
Conclusion
In order to ensure fire safety levels in trade buildings, it is essential to follow the prevailing rules, regulations, and standards of building in the UK. Of significant interests are the five categories of fire safety such as the means of escape, internal fire spreads (structure), internal spread of fires (linings), external fire spreads, and finally yet important, the ease of facilities and access to the fire service (Mike, 2009). Trade buildings should be built to conform to the requisite building standards and regulations in addition to conducting fire assessment measures aimed at determining the safety index and priority of necessary actions that must be undertaken to improve the situation (Jinhua, & Guanquan, 2008). In the UK, the Communities and Local Government is responsible for providing policy regulations in fire safety in trade buildings. These policy regulations are covered under the Fire Safety Order 2005. For this reason, owners of trade buildings are expected to conduct a risk assessment study to ascertain the level of fire safety in their premises and as well, implement measures to caution, protect, and uphold management of fire spreads.
Appendix 1: How fire spreads.
Appendix 2: A case of fire spread that occurred in West Coast Sporting Goods at 13720 E 14th St. on Friday, August 17, 2007.
Appendix 3: comparison of UK households in homes built according to the 2006 building regulations:
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