Fire Behavior in Compartment with Failure of Passive and Active Systems - Term Paper Example

Fire behavior in compartment with failure of passive and active systems Name Course Name and Code Instructor’s Name Date Abstract This paper discusses the behavior of fire within high rise building through compartments, vertically and horizontally. The discussion and analysis will go through the ignition, growth and flashover and how it will spread to other compartments vertically and horizontally with combination of the failure of active systems like sprinkler system and even alarm system. More ever, the failed passive system such as poorly maintained fire resistant doors and glass facade with poorly maintained fire stopper will act significantly different against the safety designed expected behavior. The difference between the expected fire behavior according to prescriptive codes and the actual fire behavior will also be discussed. The importance of applying enforcement law will be eliminated. Introduction In many applications, there is a mistaken thought that applying the fire prescriptive code will ensure safety in buildings. In the third world where there is a problem of applying enforcement law to mandate the owners to maintain their properties to achieve accepted level of performance toward the environment and fire safety. However, after the completion of new projects, which is approved to be code compliance; both passive and active systems will need for maintained regularly. After few months, these systems will need for the first maintenance and if the enforcement law of maintenance is absent, then the building will perform in a different way than was initially anticipated through the prescriptive code. This because the prescriptive codes that are issued according to certain data does expect certain level of system performance that will lead to an accepted level of safety. However, in this case while both active and passive systems are failed because of lack of proper maintenance actions coupled with the absence of law enforcement results in poor performance and decreased safety. Enforcing law for maintaining the building will proof to be essential in these countries. Meanwhile and until enforcing the law, the fire management of the building should be revised by either having more strict prescriptive code which involve data of failure possibility or revising the performance of the fire stations and the ability of arriving to the site (time response) and evacuation time according to structure surviving ability. The report will explicitly analyze the behaviour of fire within high-rise building through compartments, vertically and horizontally with failure of both passive and active systems. Fire Behaviour in buildings According to Gustin (2010), understanding the behaviour of fire in a building is a critical step in understanding the best technique and strategy of responding to it and eventually confining and stopping the fire from spreading. To fully, comprehend the significant function learning fire behaviour plays in fire risk assessment and effective response to fire emergencies, it is important to mention the underlying factors that lead to ineffective fire response, which leads to catastrophic consequences such as loss of life and extensive spread and damage of fire. These underlying elements includes insufficient risks assessment, lack of accountability on part of the owner in securing fire safety measures and fire response agencies in responding to the fires and failed communication during fire response operations. Moreover, failed Incident Command from initial response, unproductive SOPs and inadequate situational awareness, lack of the capacity to confine fire in the room of origin as indicated by Cote (2003). In addition, lack of adequate resources to confine and extinguish fire efficiently, inadequate training for fire crews, and divergence from set operating guidelines and non-compliance to safety working procedures as mentioned by Harmon & Kennon (2005). Among indicators of fire behaviour in buildings, include the flame that encompasses the flaming combustion, smoke patterns and conditions of the smoke, air track that encompasses air movement, building elements that encompasses construction materials, building content and building features, heat that encompasses changes in temperatures, which are essential in reading fire in order to assess the risk (I.A.F.C. & N.F.P.A. 2009). Spread of fire to other compartments vertically and horizontally with combination of the failure of active systems like sprinkler system and even alarm system According to Milke, et al., fire behaviour differs significantly throughout a premise with various compartments of the building being on the different stages of fire development. Active systems entails fire prevention and response machineries meant to respond to fire through activation facilitated by use of sensors and mechanical methods such as fire extinguishers, sensors, fire sprinkler systems, notification systems, smoke detectors, water supplies, automatic fire suppressors and alarm systems. Passive systems entail fire resistant systems used in the layout of the premises and consist of materials used for building such as fire resistant doors, partitions to confine fire, glass facades with fire stoppers, wide stairways to facilitate swift evacuation, spray on fire roofing among others (Fitzgerald, 2004). When these systems fail to function as purposed, they alter the expected fire behavior compromising the life of occupants and enhancing the damage on properties. Failure of active and passive system are caused by poor assembling during manufacturing meaning that the systems have not passed quality assurance tests, damage in earthquakes and other means of destruction and poor installation owing to poor expertise and skills by the installing technicians. In addition, lack of effective repair and maintenance due to negligence or due to tear and wear of the fire alert and prevention systems caused by irregular serving and poor maintenance work (Harmathy, et al., 1979). Fire development stages Fire in buildings normally develops through a standard process that involves the incipient stage, which characterises the beginning of the fire either by a spark or by even an unattended cigarette butt. It is followed by the growth stage, which is accelerated by a flashover, which entails a swift move from the growth to the next fire development stage (Grimwood, 2008). After the growth stage of fire development, there is the fully developed stage that is followed by the decay stage. Important to mention is that fires in compartment do not necessary have the fire development stages follow each other in sequence due to unplanned ventilation, characteristics of the fuel and heat release rates (Franssen, 2010). Fire behaviour at the inception stage with failed active and passive systems Different fires behave differently at various stages of fire development. It is no different at incipient stage depending on the prevailing conditions. With sufficient supply of fuel, oxygen and heat, the fire is more likely to intensify, gain the capacity to spread and progresses into the growth stage of fire development (I.F.S.T. 1992). On the other hand, insufficient supply of fuel, heat and oxygen facilitated by effectively and fully functioning active systems and regularly maintained passive systems, the fire is more likely to lack the capacity to keep alight and eventually burn off as indicated by Gustin (2010). The fire alert and protection systems, contents of the compartment, ventilation determine the swiftness with which fire moves from the incipient stage to the growth stage. Fire behaviour at the growth stage with failed active and passive systems Fire behaviour in the growth stage is characterised by heating of the gases in the compartment, increment in pressure, inward movement of air from exterior of the compartment due to low pressure on the cool gas layer and fire intensification through spreading of the flame and detonation of other fuels within the room (US.F.S. 1972). The prevailing transfer of heat within the compartment with fire transits from convection to radiation as radiant shift in heat enhances heat flux at the level of the floor (Milke, et al.). Flashovers are more often than not, able to influence the behaviour of the fire in the growth stage and speed it up to the fully developed fire stage. Effective active systems and fully maintained passive systems prevent the growth stage from transiting to the fully developed fire stage. Fire behaviour during Flashovers with failed active and passive systems Flashovers can be defined as the rapid shift to the fully developed fire from the growth stage of fire development (Kirk & DeHaan, 2007). Flashovers normally happens when all combustible materials and fuels in a fire compartment are ignited and the supply of oxygen increases. In most instances, flashovers are characterised by ceiling temperatures exceeding 500 degrees Celsius that blend with a heat influx at the floor level not less than, 115 kW/m2, which push out any air tracks within the compartment at a very high force and velocity (D.C.L.G. et al., 2009). Flashovers may not necessarily occur in compartment fires but prevailing conditions such as highly combustible building materials, adequate fuel, ventilation, fire load and heat release rates can necessitate the occurrence of a flashover (Harmon & Kennon, 2005). Flashovers mostly occur in buildings and premises with failed active systems and poorly maintained, passive systems, where the systems fail to alert and respond to fires as expected. There must be adequate heat of combustion and high rate of heat release for flashovers to occur. Not every instance that ventilation is enhanced does a flashover occurs (Quintiere, 1998). Increment in ventilation has to be supported by favourable fire conditions and building composition in order to induce fire behaviour attributed to a flashover, which are enhanced by failure of fire alert and prevention systems (D.C.L.G. et al., 2009). Fire behaviour during the fully developed fire stage with failed active and passive systems The fire behaviour in the fully developed fire stage is characterised by high release of energy, build up of un-burnt gases at the ceiling that recurrently burns as the flames are pushed out of openings, which are therefore seen in wall openings, doors and windows (LLC, Books. 2010). The fire at this stage burns with high intensity and the temperature of the gases at the compartment amounts to more than seven hundred Celsius (US. F.S. 1972). In the fully developed fire stage of fire development, the fire burns at a steady rate and the mass loss rates are comparatively constant. Due to the nature of fuel and restricted supply of oxygen at the fully developed fire stage can result in an equilibrium situation as indicated by (O’Connor, 2008). Ventilation controlled burning refers to when the rate of mass burning surpasses the amount that can be sustained by present supply of oxygen. Fires in fully developed fire stages in compartments with inactive and passive systems have constant conditions at the upper level of the ceiling, which includes uniform conditions of the heat influx and thermal characteristics of the smoke (US.F.S. 1972). In long compartments or compartments with large areas/ spaces, fires behave differently. Fires continue to burn in the points closest to the air vent that supply oxygen while the temperatures of the smoke tend to be highest at the same points as noted by Fitzgerald (2004). Conversely, the heat flux in such areas does vary across the entire area where the fire is developing. Fires in the decay stage behave similarly to the inception stage as the prevailing conditions such as availability of fuel and oxygen supply determines whether the fire will grow or fade out. Case study one This case will analyze fire behavior in building with failure of both passive and active system. The fire behavior of any building is highly influenced by the burning behavior of the building materials and mass loss (N.F.P.A. 2006). Additionally, the heat release rates, the fire development stages namely inception, growth, fully developed fires and decay stages, intensity of temperatures, fire alert and response measures and techniques and the ventilation profile as highlighted by Quintiere (1998). A case study is the World Business Center. Due to failure of the fire alarm systems, notification appliance circuits, telephone circuits, smoke management systems and failure of the stair pressurization, there was delayed notification of the impact to the occupants in September 11. The active and passive systems failed to help ease communication between the occupants who had been trapped in the building with the firefighting crew to aid rescue operations. There was performance degradation of the systems, which limited rapid notification, response and rescue from the monitoring company. The fire response team did not know the location of the fire since the fire alert systems did not function as designed owing to damage caused by the impact while smoke easily spread through the building as none of the smoke management systems were functioning due to the impact. This hindered rescue operations and it increased the risks of more deaths and casualties due to suffocation and transfer of fire through radiation. Case study 2 This case will analyze fire behavior in high-rise building with failure of both passive and active system. High-rise buildings are high-risk premises especially to fire emergencies as described by (US.F.A.). Fire safety in high-rise compartments need to factor in the height, design and specifications of the building and complexities that emerge in evacuating and responding to fires in such high-rise compartments (O’Connor, 2008). A case study building is 2010 Shanghai fire, high-rise apartment building that met fire safety and earthquake requirements. The building has two separate stairways that have smoke pressurized systems. The building has automatic sprinkler systems, separate air handling systems in each floor, smoke detectors, fire dampers, separate single zone lifts, and fire service control of lifts, protected shafts and refuge areas in stairs. The building represents a typical tall building with a podium, pre-cast concrete floors, beams and columns installed as earthquake resistant. On alarm activation, the fire dampers, pressurization systems and smoke control are activated. The building has vents joining compartments to the outside. Therefore, incase of an earthquake and an after fire, the expected fire behavior changes owing to damage caused on the active and passive systems due to impact of the earthquake as the sprinklers may fail to operate due to water shortage while smoke may spread owing to failure of the stair enclosures, increasing the risk on occupants. Damage on alarm systems may hinder activation of fire dampers, pressurization systems and smoke control thus, making it hard to confine the fire. Debris such as wood may fuel the fire and through radiation cause fire to move to adjacent compartments above the fire compartment. Nevertheless, fire may be restricted by hindrances such as concrete and limited supply of air. Ignition of fire and its growth in this case study is dependent on fire sparks by cut electric circuits, use of electrical appliances by trapped occupants and flammable materials that can catch fire through radiation and convection. Fire response measures and programs for high-rise compartments can be designed based on the type, size and height of the premises, separation between high-rise compartments, number and types of windows in each floor, capacity of the building and the vertical separations between windows (Craighead, 2009). Case study 3 This case will analyze fire behavior in high-rise building with failure of both passive and active system Horizontal spread of fire in high-rise compartments mostly occurs at the curtain wall as suggested by Ying (2008). If fire is permitted to transits from the growth stage to the fully developed fire stage that has gas temperatures amounting to more than one 1000 degrees Celsius due to failure of active systems, the room has the potential to produce flames that extend to more than 6 feet above the window (US.F.A.). The extended flame can easily catch on curtains and combustible materials in the floor/ room above the combusting room, which can then progress through the fire development stages if inefficiently and poorly handled or responded to (Ching, et al., 2007). According to Harmathy et al. (1979), the high heat intensity of hot gases on the ceiling level of the fire compartment has the capacity to produce enough pressure to break windows on the upper floor/ room and through fire sparks thrown by flames and smoke, ignite fire on the upper floor. The case study is the Woolworths Building in Kenya installed with fire extinguishers and alarm systems as the only fire response systems in each floor. The floors are carpeted with PVC; the occupants have access to one-way staircase with wooden handrails and one elevator shaft that run on electricity. Each compartment in each floor has glass windows with curtains and fire response team is notified through fire service telephone systems. Each floor has fire response instructions to be read by occupants. Incase of a fire emergency, the notification is more likely to be delayed as notification is done manually by making a call to the response unit. The fire spread vertically, horizontally is easier due to the PVC carpeting used, and easily catches on from one floor level to another through curtains. The wood handrails in staircase would make fire spread easy and evacuation difficult. Communication to the outside is made more difficult by damage to power cables and communication circuits. Pressure from hot gases accumulated on the ceiling of fire compartment can easily break the glass windows on the top floor. Once un-burnt gases are able to escape to the exterior of the fire compartment, they are exposed to enough supply of oxygen automatically igniting a flame outside the room, which can project outwards and upwards into the broken windows in the upper floor level as supported by I.F.S.T. (1992). Conclusion The report has discussed fire behavior in high-rise compartments with failure of both active and passive systems. The behavior of fire in varied instances differs extensively depending on heat release rates, fuel and supply of oxygen. An increased supply of these elements results in fire intensification and transits of fire from one fire development stage to the next. Active systems and passive are designed and installed with the anticipation they will function as purposed and thus react appropriable and efficiently, to expected fire behavior. Therefore, when the systems either due to system failures and malfunctioning due to poor repair and maintenance fails, they alter fire behavior which has catastrophic results. Fire easily spreads vertically and horizontally through direct contact of flame with combustible material, convection, conduction and radiation. Fire develops in four stages namely inception, growth, and fully developed fire and decay stages. Fire is sustained through sufficient oxygen supply and through thermal layering. As discussed in the report, flashovers occur when flammable matter heat up and burn in a closed area initiating a roll over. Expected fire behaviors can easily, be managed with installation of effectively functioning active and passive systems to alert, prevent, respond and help in evacuation procedures. Understanding the stages of fire development, elements that fuel fire, designing buildings that consider fire safety, educating the public on fire safety and effectively putting in place fully operational active and passive systems are critical in containing and stopping fire before it cause harm and damage to people and property respectively. References Ching, F., Winkel, S.R., & I.C.C. 2007. Building codes illustrated: a guide to understanding the 2006 International building code. New York: John Wiley and Sons. Cote, A.E. 2003. Organizing for Fire and Rescue Services. Sudbury: Jones & Bartlett Learning. 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