Fire Protection: The Principle of ASET and RSET with Regards to Means of Escape - Term Paper Example

Name Course title Task Date The principle of ASET and RSET with regards to means of escape Table of Contents Introduction 3 Discussion 3 B1 – Means of Warning and Escape 3 Fire safety design process in UK 4 The assessment of designs 6 Advantages and disadvantages of FSE 6 Evacuation safety conditions 7 Available Safe Egress Time (ASET) 7 Required Safe Egress Time (RSET) 7 Response time - This is the time taken by the occupants to receive and interpret the emergency information and prepare to exit. Respond time can be reduced by providing prompt, accurate and clear information to the people. Other factors which affect response time are physical and mental state of the occupants, level of training on response to warning, role and responsibilities and how much they feel they are in danger (Peacock et al., 2011). The overall time in fire safety is summarized in the figure below. 9 Margin of safety 9 Use of models 11 Conclusion 11 References 13 Introduction There has been much consideration of the safety of people in crowded areas, due to the potential to cause hazard. Even a small fire incident can be very hazardous in a crowded place. Therefore, fire safety provisions should be design carefully in a building to allow evacuation in case of a fire occurrence (Akan et al., 2009; In Kim et al., 2014). Fire in a building may become lethal to the occupants, if the occupants are exposed to the products of fire for a long period. Evacuation time is used to determine the time required for occupants to exit to safety after recognizing fire and beginning to exit, and the success of fire safety strategies depends on timely evacuation of the occupants. Life safety in a building is determined by calculating the difference between the required theoretical time for evacuation, Required Safe Egress Time (RSET), and the time available for evacuation of the occupants, Available Safe Egress Time (ASET). The total evacuation time is the real time needed for all the occupants to be move to safety (Drysdale, 2011). Various factors are considered when dealing with the evacuation time. They include recognition time, pre-movement time, response time, walking time, flow time and travel time used in evacuation. The objective of this study is to examine evacuation time and the principle of ASET and RSET in relation to the means of escape (Papanikolaou & Soares, 2009). Discussion B1 – Means of Warning and Escape These are the guidelines for the building design, to provide for the early warning and the necessary means of escape to safety in a fire incident. This provision covers the measures needed to ensure that there are facilities that provide means of escape in a fire incident. The fire safety structure should take care of all kinds of people including the people with disabilities (Billington et al., 2002, 65 -70). The design should not rely on the rescue by the fire brigade who are outside the building. The objective of the provision is that the people who have occupied any part of the building can exit safely from the building in case of an emergency with no support from the outside (Fire Protection Association, 2014). The design is based on the expected behavior of fire, which may start any part of the building before spreading to other parts. Therefore, the building should carefully be designed to determine the threat, which may arise from fire. Fires normally start in a small part before spreading to other parts of the building, which may be spread through movement routes in the building. The safety measures that are taken may include reducing the effect of smoke and fumes. B1 requires the provision of appropriate sizes and number of routes, which can enable the occupants to evacuate to a safety in an emergency. The routes should be protected in term of enclosure, and sufficient smoke control and alarms to provide warning about the existence of fire and provide them with a means of escape depending of the height and size of the building (Billington, 2002, 66-80; Drysdale, 2011). When the provisions of the technical guidelines are not possible to be applied, fire safety engineering technique can be applied. This technique consider various aspects that include the risk of fire occurrence, the severity of fire, the available safety measures, and the risk to the people in the building in case of fire occurrence (Carroll, 2009). In the fire incident, the safety of the people depends on the emergency procedures, which makes use of the designed fire safety measures and takes account of the occupants’ behavior in an emergency. It is therefore necessary to understand the how people behave in case of a fire for effective design of the emergency procedures that overcome the occupants’ behavior (Carroll, 2009). This is aimed at making sure that the building occupants are not exposed to smoke, heat, or fire and that the people are exposed to such incidents does not develop serious problems. Fire safety design process in UK In order to ensure that the building is safe from the risk of fire, the design and operation for the building should be at high level of fire safety (Muckett and Furness 2007). The escape routes in a building in are designed based on either engineering approach or prescriptive approach. The prescriptive approach is based on the prescribed code of practice, notes from authorized person, or other documents. The code of practice that deals with fire safety is provided by fire services department meant to include escape routes in building design. The numbers of occupants are specified for the designer to determine the building occupation density, the staircase width, and travel distance, staircases in buildings with sprinklers or with no sprinklers, etc. The evacuation time to the protected area like staircase leading to the exit in a storey building should be within the calculated time of 2.5 minutes for building with no sprinklers. The building should have escape routes and build with non-combustible materials that are resistant to fire. It is assumed that the building design following these codes should be sufficient to provide protection to the building occupants in fire incident. The engineers or designers makes building design based on these codes without questioning the performance of the actual evacuation routes. However, some buildings with special features do not follow these requirements. Therefore, engineering technique is applied. In this approach, the evacuation time is estimated by considering the likely fire situations by studying the function and features of the building and nature of the occupants. The compliance to the fire safety design is checked alongside the codes of practice, before determining the expected population and the means of escape for the design (Muckett and Furness 2007). Considerations in fire safety design Various considerations should be made when designing fire safety. These can include technical consideration and human response to fire. The technical requirements include sufficient provision of the means to prevent fires, early detection and warning, means of escape, smoke control systems, fire extinguishers, control of the fire growth and others. The design of fire safety is focused at providing safe environment the building occupants (Carroll, 2009). Therefore, the provisions for fire safety include safe means of escape. The effectiveness of the means of escape in a building depends on how the time used by the occupants in case of an emergency. The response to the fire by the occupants is complex. The psychological response of the people depends on their perception about the existing situation, which in turn affect the overall escape time (Muckett and Furness, 2007). There are guidelines, which provide principles for the applications of engineering and scientific principles related to fire safety. Fire Safety Engineering (FSE) is the application that is based on the understanding impact of fire, the behavior and the response of the people in case of fire, and also how the people and the property can be protected. Fire safety engineering standards like British Standard, BS 7974: 2001, is concerned with application of engineering fire safety approach in building design and in the related published documents. The fire safety levels is based on the complex relationship between different factors that include fire initiation, fire growth and spread, the response by the occupants in the building, the surrounding environment that include the floor, walls, tables, etc., and the response by the fire detectors and other fire safety measures (Muckett and Furness 2007). Therefore the objectives of the FSE is to Minimize fire occurrence Control the growth and spread of fire Provide accessible and safe routes in case of fire. The British Standard provides the structure for fire safety engineering design by giving the guidelines and recommendations implementation of engineering and scientific principles to protect the people, environment, and property from fire. It also gives a framework for the development of criteria for the design and assessment of the building to facilitate fire safety (British Standards Institution, 2001). The assessment of designs FSE design as required by BS 7974 requires the design to be comapared with the design structure determined in quality design review. The design procedure and the initial assumptions used should ensure adequate safety level. BS 7974 provides three approaches for assessing the design. They include: The performance of the prescribed design is compared to that of the proposed design. Inherent safety factors are used to ensure that the adopted design will provide safety that is comparable to the safety achieved with the prescribed approach. A probabilistic approach that involves the likelihood of the occurrence of event, should be at acceptable low level. The analysis takes into account the likelihood of fire starting and smoke spreading to create untenable conditions in specific place in the building. A deterministic technique, which determine the worst fire scenario to be studied together with other safety factors. There should be safety factors that can ensure adequate safety level for the uncertainties in the design procedure and the initial assumptions. (British Standards Institution, 2001; McElhatton & Marshall, 2007) Advantages and disadvantages of FSE The advantages of FSE include: It provides the designer with the criteria for fire safety design It provide fire safety measures that are tailored towards specific objectives and risk It minimizes the cost of fire protection without compromising safety It facilitate innovative design in the building without reducing safety It provides the criteria for translating research into practice It compel the designers and operators to consider fire safety in the building It enables the fire safety proposal to be compared with other designs Can be used in the management of fire safety in the The disadvantages include: It require qualified and experiences personnel to assess and carry out FSE It may be restrictive It may result in the increase of design cost and time It requires data which may not be available in some fields Evacuation safety conditions The evacuation safety conditions and evacuation time can be assessed based on the relationship between RSET and ASET. The difference between the two provides the margin of safety, which is very significant in predicting the uncertainties. Available Safe Egress Time (ASET) The definition of ASET as adopted by BS 7974 is the time from the fire ignition to the moment at which the tenable conditions in the building is reached due to heat, smoke, or toxic emissions. ASET was introduced win 1983 by Cooper. ASET provides the maximum exposure time to hazard from the fire which may be tolerated with no one being incapacitated. Therefore, all of the occupants in the building should be able to escape from the building before ASET is reached (Anson, 2008). ASET is calculated as, Where is the detection time, is the time for the onset of hazardous environmental conditions, and is the notification time (Anson, 2008; Great Britain, 2008). Required Safe Egress Time (RSET) RSET (also called escape time) is the time taken by the occupants to move to a safe place after fire ignition, i.e. the target time for complete evacuation and includes the time the occupants remain safe within the time spent in the building (Anson, 2008). BS 7974: 2002 is a comprehensive document which provides a systematic technique for calculating the escape time. The proposed formula for calculating RSET is shown below. Where: is the detection time, which is the time from the ignition to the detection time by automatic systems. This may vary depending on the fire scenario, the installed fire detection system and the ability of the occupants to detect fire (Peacock et al., 2011). Alarm Time,, is the time duration between detection and pre-movement time, , is the time from detection to the time the occupants move out of the building. It includes the time the occupants recognize the alarm to the time they respond to the alarm and begin to move out. is the travel time for the occupants from the building to the a safe place, which can be determined using evacuation software simulation. Travel time can be divided into walking time, queuing time, and flow time (Anson, 2008). The travel time consist of parts, walking time and flow time. The walking time depends on the speed of the occupants during egress, while time is the times taken by the occupants to move through an exit which can be a downstairs or doorway. This includes the time taken to queue while waiting for to evacuate. The factors that affect the pre-movement time include recognition time,, response time, . Therefore, pre-movement time,, is calculated from the equation: The number of people moving through the exit will vary if they are moving at the same time or at different times. Jamming will occur if the occupants move at the same time and at the same speed, as they will arrive at the exit at the same time. The pre-movement time can be divided into the time between alarm and movement of the first occupants, distribution of the occupants when exiting, the time between the first alarms to the exiting of the last occupant (Anson, 2008). The travelling and waiting time can be ignored if the pre-movement time is long. The occupants waiting time can be improved through changing crowd density, exit selection and the number and width of the exits. Travel time is calculated from: Walking time, is the average time taken by the occupants from their locations in the building to the escape route. Queuing time,, is the time required from the alarm to the time the queue is formed at the exit. At the exit, the occupants queue as they wait for room to move forward. The speed of occupants when passing through the exit is lower than the rate at which they are arriving. The queue can be bulk or orderly queue that is based on first come first serve (Peacock et al., 2011). Flow time,, is the time taken by the occupants to move through the exit, assuming that all he occupants are at the exit at a particular time. The occupants from various areas of the building converge in an exit during an emergency. Thus, congestion occurs due to reduction in the flow rate, due to the large number of occupants evacuating at the same time. Queuing at the entrance involves a number of steps that include approaching the queue, standing or waiting in the queue and moving through the exit. The effects of waiting in a queue would affect the movement of the occupants and will lead to lengthening of the time of evacuation. Waiting time in the queue has been studied extensively. Queue time is elaborated more in time to queue formation in BS 7974, which involves waiting and moving time (Muckett and Furness 2007). Recognition time - Recognition time in British Standards is the time taken by the occupants responds to alarm. They respond after accepting that they need to respond. Recognition time varies with the charateristics of the occupants and the alarm and organization management (Peacock et al., 2011). Response time - This is the time taken by the occupants to receive and interpret the emergency information and prepare to exit. Respond time can be reduced by providing prompt, accurate and clear information to the people. Other factors which affect response time are physical and mental state of the occupants, level of training on response to warning, role and responsibilities and how much they feel they are in danger (Peacock et al., 2011). The overall time in fire safety is summarized in the figure below. Margin of safety This is the time difference between ASET and RSET. If the value of ASET is greater than RSET, the evacuation route will be considered suitable. The outcome will be forwarded to the authorities for approval. From the formula, the delay before beginning evacuation would expose the occupants to vulnerability. The behavior of the occupants during evacuation would affect their movement in case of fire, and the response is affected by the psychological and the physical state of the occupants at the time of fire recognition (Peacock et al., 2011). The figure showing the relationship between ASET, RSET and evacuation time Before exiting, most people have tendency to take preservative action like collecting valuable or important items. When estimating, it is important to take into account the occupant’s cognitive function ability. Some people may not take the seriously the audible fire warning, but they wait for further information for example clarification by the management through a phone call or notification from a neighbor before beginning to evacuate (Muckett and Furness 2007). Thus, when fire-engineering technique is used in designing the escape route, it is essential to recognize the behavior of the occupants in a fire incident such that can be included in calculating the egress time. Nevertheless, the value varies with uncertainties and accurate understanding of the occupants should be obtained. The determination of usually involves a lot of discussion by the engineers or designers with the authorities. Other considerations include the physical conditions and distribution of the occupants, the age, gender, and other conditions, are very important parameters used to estimate. There is however no universal guidelines for the determining this parameter by the fire engineering technique, which leads to arguments between the designers and the authorities (Peacock et al., 2011; International Conference on Pedestrian and Evacuation Dynamics & Klingsch, 2010). Use of models Analytical models can be used to study the behaviuor of fire and to develop fire safety measures. The models are based on mathematical relationships required for some fire conditions to occur. Computer based models can also be used to predict fire behavior and it effects. When using these models for analysis, there should be an understanding of limitations, assumptions, parameters, proper application and accuracy of the data input and interpretation of the result (In Fischhoff, 2011). The worst fire location and scenarios are envisioned by reviewing the operation and function of the building. Fire engineers usually consider the effect of stack and wind that affect the development and movement of fire and smoke. The parameters for calculating the spread of fire and smoke are based on the experimental equations provided in the design guidelines. Field simulation like fire dynamic simulator (FDS) can be used to determine the probable situations of the building in case of an emergency. The unsustainable situations can be found from thermal radiation, an enclosed temperature and the smoke layer. The time between the ignition and the beginning of the untenable situations will be considered to be the ASET for the people in the building. FDS tool enhances the accuracy and capabilities of implementation and management of the fire safety document (Goglia, Halford, Stolzer, 2012) Conclusion The provision of safe evacuation time in a building involves design and establishment of the means of safety in case of fire. The main components in the evacuation time, which include RSET and ASET, have been reviewed. The study has provided a clear overview of the ever of the process of evacuation. The developments of these components were also discussed. Others factors which affect the evacuation and RSET include the psychological effects of the occupants such as response and recognition time. The human behavior including the actions taken by the occupants when evacuating would affect the movement of the occupants. Waiting time in a queue is the dominant factor in a crowded place. References Akan, O., Sahni, S., Shen, X. S., Zomaya, A., Cao, J., Coulson, G., Palazzo, S., ... Dressler, F. (2009). Complex Sciences: First International Conference, Complex 2009, Shanghai, China, February 23-25, 2009, Revised Papers, Part 2. Berlin, Heidelberg: Springer Berlin Heidelberg. Anson, M. J. P. (2008). Handbook of Alternative Assets. Hoboken: John Wiley & Sons. Billington, M. J., Ferguson, A., & Copping, A. G. (2002). Means of escape from fire. Oxford: Blackwell Science. British Standards Institution. (2001). Application of fire safety engineering principles to the design of buildings: Code of practice. London: BSI. Carroll, R. (2009). Risk management handbook for health care organizations. San Francisco: Jossey-Bass. Drysdale, D. (2011). An introduction to fire dynamics. Chichester, West Sussex: Wiley. Fire Protection Association, (2014). Fire Safety and Risk Management: For the NEBOSH National Certificate in Fire Safety and Risk Management, Routledge Goglia J. J., Halford C. D., Stolzer A. J., (2012). Implementing Safety Management Systems in Aviation, Ashgate Studies in Human Factors for Flight Operations, Ashgate Publishing, Ltd. Great Britain. (2008). Fire safety risk assessment: Educational premises. London: Department for Communities and Local Government. International Conference on Pedestrian and Evacuation Dynamics, Peacock, R. D., Kuligowski, E. D., & Averill, J. D. (2011). Pedestrian and evacuation dynamics. New York: Springer. International Conference on Pedestrian and Evacuation Dynamics, & Klingsch, W. W. F. (2010). Pedestrian and evacuation dynamics 2008. Heidelberg: Springer. In Fischhoff, B., In Brewer, N. T., In Downs, J. S., & United States. (2011). Communicating risks and benefits: An evidence-based user's guide. International Conference on Pedestrian and Evacuation Dynamics, Peacock, R. D., Kuligowski, E. D., & Averill, J. D. (2011). Pedestrian and evacuation dynamics. New York: Springer. McElhatton, A., & Marshall, R. J. (2007). Food safety: A practical and case study approach. New York: Springer. Muckett M., Furness A., (2007). Introduction to Fire Safety Management, Routledge International Conference on Advances in Engineering Technologies and Physical Science, In Kim, H.-K., In Ao, S.-I., & In Amouzegar, M. A. (2014). Transactions on engineering technologies: Special issue of the World Congress on Engineering and Computer Science 2013. Muckett M. and Furness A., (2007). Introduction to Fire Safety Management, Routledge Papanikolaou, A., & Soares, C. G. (2009). Risk-based ship design: Methods, tools and applications. Berlin: Springer. Read More

When the provisions of the technical guidelines are not possible to be applied, fire safety engineering technique can be applied. This technique consider various aspects that include the risk of fire occurrence, the severity of fire, the available safety measures, and the risk to the people in the building in case of fire occurrence (Carroll, 2009). In the fire incident, the safety of the people depends on the emergency procedures, which makes use of the designed fire safety measures and takes account of the occupants’ behavior in an emergency.

It is therefore necessary to understand the how people behave in case of a fire for effective design of the emergency procedures that overcome the occupants’ behavior (Carroll, 2009). This is aimed at making sure that the building occupants are not exposed to smoke, heat, or fire and that the people are exposed to such incidents does not develop serious problems. Fire safety design process in UK In order to ensure that the building is safe from the risk of fire, the design and operation for the building should be at high level of fire safety (Muckett and Furness 2007).

The escape routes in a building in are designed based on either engineering approach or prescriptive approach. The prescriptive approach is based on the prescribed code of practice, notes from authorized person, or other documents. The code of practice that deals with fire safety is provided by fire services department meant to include escape routes in building design. The numbers of occupants are specified for the designer to determine the building occupation density, the staircase width, and travel distance, staircases in buildings with sprinklers or with no sprinklers, etc.

The evacuation time to the protected area like staircase leading to the exit in a storey building should be within the calculated time of 2.5 minutes for building with no sprinklers. The building should have escape routes and build with non-combustible materials that are resistant to fire. It is assumed that the building design following these codes should be sufficient to provide protection to the building occupants in fire incident. The engineers or designers makes building design based on these codes without questioning the performance of the actual evacuation routes.

However, some buildings with special features do not follow these requirements. Therefore, engineering technique is applied. In this approach, the evacuation time is estimated by considering the likely fire situations by studying the function and features of the building and nature of the occupants. The compliance to the fire safety design is checked alongside the codes of practice, before determining the expected population and the means of escape for the design (Muckett and Furness 2007). Considerations in fire safety design Various considerations should be made when designing fire safety.

These can include technical consideration and human response to fire. The technical requirements include sufficient provision of the means to prevent fires, early detection and warning, means of escape, smoke control systems, fire extinguishers, control of the fire growth and others. The design of fire safety is focused at providing safe environment the building occupants (Carroll, 2009). Therefore, the provisions for fire safety include safe means of escape. The effectiveness of the means of escape in a building depends on how the time used by the occupants in case of an emergency.

The response to the fire by the occupants is complex. The psychological response of the people depends on their perception about the existing situation, which in turn affect the overall escape time (Muckett and Furness, 2007). There are guidelines, which provide principles for the applications of engineering and scientific principles related to fire safety. Fire Safety Engineering (FSE) is the application that is based on the understanding impact of fire, the behavior and the response of the people in case of fire, and also how the people and the property can be protected.

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