Strategies of Design for Fire Safety Amid Practical Environmental and Economic Constraints - Report Example

Fires cause great losses including loss of life and damage to properties. It is, therefore, very essential that buildings, more so, multi-storied building are designed and constructed to standards that allow fire safety. Take for instance, an intelligent building comprising 20 storey block, and multi-occupied (such that one half is hotels while the other is offices) that is to be constructed in the centre of Preston city. It is vital to consider building construction methods and materials, design strategies including the need for smoke movement, and the kind of extinguisher to use so as to make the building relatively safe in regards to fires. Building construction methods and materials There are various construction considerations that would be utilized to raise an intelligent building. In regard to fire safety, the design of the multi-storied described above could have necessitated the need for compartmentation, structural integrity, and incorporation of systems for fire protection. Proper compartmentation is vital in limiting smoke and fire spreads, and transmission of heat. This could be achieved through, for instance, floor to ceiling wall or assembly as a barrier. The assembly, per se, need to adequately insulate the sides that are not exposed to the fire from heat transmission. The curves for fire exposure, moreover, should not underestimate durations and temperatures of fires. Also, it is essential that the building has the structural integrity to withstand a fire. The goal is to prevent the support structures from succumbing to the effects of fire. Therefore, the assembly should have the capacity to support the weight of both the “structure and its contents” (National Institute of Standards and Technology 2009). So assessment of the mechanical properties associated with the structural element under increased temperature and thermal strain is essential so as to establish structures that would support specific loads under such circumstances created by a real fire. It is the goal of fire safety in building to minimize fuel load. In construction of the building, the use of materials such as wood and plastic should be minimized and should not feature in support structures. Concrete and steel are widely useful in constructions. Since steel is weakened by fire, it is important to increase its resistance. Concrete and brick, therefore, could be applied at appropriate thickness to cover steel. What is more, other enclosures including spray-based insulation could be used. Materials like gypsum that are used for finishing should be enclosed as well. Strategies of design for fire safety amid practical environmental and economic constraints It is challenging to construct a building that has fire safety features without additional expenses to the initial costs of a basic design. Nonetheless, it is justifiable to design buildings that incorporate fire safety elements when the cost of a fire occurrence are considered. With this in mind, therefore, there are various design strategies for passive fire protection. Note that passive protection entails incorporating measures within the structural design of a building. The main aspects in passive fire protection include use of suitable materials that are resistant to fire, dimensioning of the building elements, use of “fire protection materials”, and compartmentaion” (National Institute of Standards and Technology 2009, 1). The goal of these design strategies is control the spread and effect of fire through provision for fire resistance and ultimately allowing maintenance of structural integrity for a specific time period. Effective control of fire spread in a building requires proper compartmentation where interior spaces have barriers. As such, compartmentation should feature partitions that are tested for fire resistant and sufficiently protected against fire penetration. These divisions prevent channelling of hot gases, flames, and transmission of heat to the sides that are not exposed. Therefore, it is necessary to have the barriers run across from the floor to the ceiling. Architectural designs are also vital in combating the spread of fire. It would be useful, therefore, to consider orientation, window size, and spacing between floors as aspects that would influence fire spread. Note that large windows that are narrowly spaced between floors are generally likely to cause more fire spread vertically than smaller ones separated by bigger spandrel panels. It is useful, in addition, to protect areas under fire risk with fire resistant materials and locating them in such a way that in case of fire, it does not spread very easily to other areas. Active fire protection is also vital. In this respect, fire detection and protection systems should be installed. These include sprinkler systems; fire, heat and smoke detectors with alarm systems; and notification vibrators. The need to control smoke movement Smoke in a building is as dangerous as the fire itself, and it is in this regard that controlling smoke movement is vital. Neglecting smoke control may undermine the very objective of fire safety in a building. Generally, smoke will follow open spaces including stairwells, elevator and ventilation shafts, and seismic joints. Therefore, it is important in the design of the intelligent building to incorporate systems that would ensure smoke does not spread in such directions. Normally, smoke control systems are a mix of methods including pressurization, exhaust method, and passive control. A pressure sandwich, for instance, can be utilized to control and pump out smoke from floors that are already exposed to fire. The pressure sandwich features floors and walls that are firmly sealed, and a mechanism for pumping smoke out. Therefore, smoke zones are created such that the floor under fire is negatively pressurized while the adjacent unexposed floors maintain positive pressure. This creates a pressure difference that is sufficient enough to prevent smoke leakages from the affected areas. To control smoke movement the building should be characterized by positive pressurization of the elevator ducts or rooms and stairwells to avoid smoke intruding into these sections; draining smoke out from the areas exposed to fire, smoke containment within a specific zone through smoke-tight partitions and closing openings in these partitions, shutdown of fans that re-circulate smoke, early smoke control activation, and separation of fan inlets, and exhaust outlets to avoid smoke re-introduction into the building. Installation of devices for control of smoke movement is also essential. These devices include fans; ducts; doors and dampers; heat, area or duct detector; sprinkler switches and system; hoods for pressure relief; and other devices useful in smoke control. Fire extinguishing agents and their advantages and disadvantages There are several fire extinguishing agents that are useful in controlling or extinguishing fires. In extinguishing fires, it is essential to determine the class under which a fire falls or rather the cause of the fire. Fires are classified as follows in the United Kingdom: Class A fires are caused by simple or organic materials such as papers, wood, etcetera, Class B fires are caused by flammable liquids such as petroleum products Class C fires are caused by flammable gases Class D fires involves combustible metals like sodium, and etcetera Class E fires involves electrical faults or items. Class F fires involves cooking oil and fat. The most common agents include water, dry and wet chemical agents, carbon dioxide (CO2), foam including aqueous film forming foam (AFFF), Halon, and dry powder. Almost all agents including water, foam, dry powder, and wet chemical are capable of extinguishing class A fires. However, water is suitable in extinguishing Class A fires due to cost factors. Carbon dioxide, dry powder, foam and Halon gas are applicable to class B while dry powder is useful in class C fires. It is worth to note that Halon use is illegal in the United Kingdom unless under specific circumstances (envirowise 2008). What is more, Halon agents are associated with environmental degradation and, therefore, are generally not suitable for use. Dry powder specific to class D fires is utilized for this class of fires. There certain advantages and disadvantages associated with the use of specific fire extinguishing agents. Water, for instance, is suitable because it is inexpensive, non-toxic, plentiful, can remove heat, and is effective for the class A fires. However, water conducts electricity and is not suitable for class E fires; in fact, it may result to further spread of this type of fires. What is more, water can carry toxic materials with run-off, and elsewhere, it freezes during the cold seasons. The advantages of carbon dioxide is that it leaves no residue, is relatively inert, and can minimize oxygen to a level below 15 %. In contrast, carbon dioxide has it disadvantages: in general, more than 35% volume in CO2 concentration is required to effectively flood fire; at certain percentage of concentration CO2 become poisonous to humans; it dissipates quickly, therefore allowing reflash; collects in low areas and pits; and some electronic gadget be suffer its cooling. Dry chemical agents stops chemical reactions and are generally not toxic. It is most effective and suitable on class B and class C fires. Advantageously, dry chemical agents leaves residue, obscures visibility, soaks up moisture and could cake inside container, are potential irritants, pressure application can cause liquids on fire to splash, and are not suitable on class A fires that are deep-seated. Agents like mono-ammonium phosphate are corrosive. Halon 1301 and Halon 1211 are can be used for fire extinguishing. They are effective to class A, class B, and class c fires. Halon 1301 is not severely toxic at volume below 10 percent, does not leave residues, has no chilling effect on electronic gadgets, and usually applied at above 7 percent by volume. Halon 1211 leaves no residue, can be used as sprays and in portable extinguisher cans. Their disadvantages, however, include production of toxic products after interaction with fire, collects in low areas and pits, known to deplete the ozone layer. Both are toxic at level above 10 percent by volume for Halon 1301 and above 4 percent by volume for Halon 1211. In addition, Halon 1211 must be utilized at volume above 5 percent while Halon 1301has harmful effects that manifest after a delayed period. Recommendation and conclusion Both passive and active fire safety measures are essential in a building. The passive measures entails incorporation of fire safety mechanisms within the structural design of the building. These passive measure are complimented by the active fire protection measures which include alarm systems, use of fire extinguishers and evacuation strategies. In this respect, the intelligent building should feature the structural design as discussed above where compartmentation, structural integrity, and smoke-tight sealing are adhered to so as to ensure fire safety. Additionally, the active fire protection should consider fire extinguishers where specific fire extinguishing agents are specific to certain class of fires. All the agents discussed above are suitable for the specific class as discussed above. Therefore, water should be applied to class A fires, carbon dioxide and foam to class B, dry powder to class C and class D fires. Although Halon is suitable for class B and class C fires, it is not environmentally friendly and is toxic to human at certain percentage of volume. In fact, its use is banned in the United Kingdom, but allowed in special satiations. It is important that the correct fire extinguishing agents is used for a particular fire to avoid causing more tragedy. References Aktan, A. E, Kehoe, B and Ellingwood, B. R 2007, Forum: Performance-Based Engineering of Constructed Systems, Journal of Structural Engineering, Vol. 133, No. 3, United Kingdom. Babrauskas, V 1996, Fire Modeling Tools for Fire Safety Engineering - Are They Good Enough? Journal of Fire Protection Engineering, vol. 8, No. 2, United Kingdom. British Steel Plc. 1999, The Behaviour of Multi-storey Steel Framed Buildings in Fire, Swinden Technology Centre, United Kingdom. Buchanan, A. H 2001, Structural Design for Fire Safety, John Wiley and Sons, Limited, United Kingdom. Envirowise 2008, Disposal of Halon, 13th march 2009, National Institute of Standards and Technology 2009, Best Practice Guidelines for Structural Fire Resistance Design of Concrete and Steel Buildings, National Institute of Standards and Technology, United States. Read More