The Principles of ASET and RSET - Coursework Example

RSET and ASET Name Date Course RSET and ASET Introduction The risk of fire in building is common due to the nature of activities and the electrical installations in the building. Fire in a building can be caused by several factors and it may lead to the total destruction o property and loss of life. The building design is has to consider the concepts of fire safety in accordance with the codes that are in place. Several codes are in place for the purposes of providing guidance during the fire safety design. The British standards provide for the codes of safety in the United Kingdom and it is also used in other parts of the world. BS 7974 is usually applicable during the identification and definition of one or more fire safety designs (Chow, 2013). A disciplined approach to the fire safety engineering can be achieved through the use of the codes. It is however important to note that the engineers and must consider the legal issue apart from using the BS codes. Available safety egress time (ASET) is also important during the design of the fire safety. This is because it provides the calculations that are required for ensuring that the safety is enhanced. It is the responsibility of the engineers to ensure that they comply with requirements of the codes so as to ensure that the safety is enhanced in case of a fire. The issues of tenability have to be considered during the design to avoid maximum damage. The paper thus discusses the principles of ASET and RSET with regards to means of escape. Discussion ASET and RSET ASET is the available safe egress time and it involves the amount of time that elapses from the ignition of the fire to the development of untenable condition. The untenable condition is the time that the fire has the ability of causing incapacitation. The empirical correlation of fire modeling is usually applied during the determination of ASET. It is also important to note that the combustibles present and their associated product yield have to be established as the first process of the product yield. The design fire is also considered as the heat release history. The product yield of the combustion process is the primary soot and carbon monoxide. The soot and carbon monoxide have the ability of affecting the escape of the people in the building after the ignition. The next process in ASET is to determine the time after which the space that the occupants can escape through becomes untenable (Yao, et al, 2013). A calculation tool such as the fire model can be used in this case. The untenable condition is usually as a result of smoke and heat. This is considering that smoke blocks the vision and it also reduces the amount of oxygen and hence causing suffocation in the process. A condition is said to become untenable when the amount of smoke or heat calculated through the fire model has exceeded the pre-established tenability criteria. It is usually impossible for the occupants to escape from the building after the conditions have become untenable. RSET is the required safe egress time and it is the amount of time from ignition that is required for the occupants to evacuate a building and to reach the building exterior or protected exit enclosure. Various factors may affect the RSET including the height and size of the building. RSET is also considered as the sum of the alarm time, the evacuation delay time and the movement time (Bjelland & Borg, 2013). The alarm time is considered as the time that the occupants become aware of the fire through and automatic or manual fire alarm of the building. The evacuation delay is the time that elapses between the time the occupants are aware of the fire or after the alarm and the time that they decide to make the decision to evacuate. The pre-movement activities involve the time that the occupants investigate whether the fire is real, when they gather their belongings or when they start looking for their friends or family members. Various factors may affect the pre-movement period including the nature of occupancy. The movement time is the time that the occupants reach the protected exit enclosure or the exterior of the building. The walking sped as well as the occupant flow rates affects the movement. This is considering that the occupants may have to pass through stairs, doors and corridors. The FDS-EVAC modeling can be used for the purposes of calculating the movement time. A factor of safety has to be applied during the calculation of RSET due to the uncertainties of the human behaviors. During the design for fires safety, ASET/RSET concepts have to be considered. Different tools can be used during the process of calculating ASET and RSET. The provision of fire suppression system as well as providing an active or passive smoke control system may lower the ASET. The provision of adequate separation distances between the fuel packages can also play an essential role in ensuring that the ASET is increased. A customized fire protection and life system can be developed through the considering the different aspects of ASET and RSET (Chow, 2013). The strategic placement of the smoke detectors can also play an essential role in dealing with RSET. A voice occupant notification can also be placed in different rooms for the purposes of ensuring that the occupants are able to know about the fire and its location or part of the building. This will play an essential role in reducing the pre-movement time. The pre-movement time is usually increased due to the lack of adequate information about the fire. On the other hand, it is also important to note that the presence of effective communication within the building is useful in reducing the pre-movement period. Placing the exit signage in a building is also important in terms of reducing the movement. On the other hand, it is important to note that the proper arrangement of the means of egress can be useful in reducing the pinch points and excessive queuing which affects the movement. The consideration of fire safety can be useful in ensuring that the lives of are saved in the event of a fire. BS 7974 assumes that the provisions in the fire safety engineering strategy will be maintained and implemented throughout the life of the building. This is considering that the risk of fire can occur at any time during the life of the building. Understanding the concepts of ASET and RSET is important in ensuring that the building characteristics do not support the fire but instead slows down the fire. During the design of a building, it is important to ensure that no room is used for the purposes of getting to the other. This is because of the difficulties that it may lead during the evacuation process. On the other hand RSET is also affected when the occupants have to pass through other rooms before they reach the exit. Protected stairways together with additional smoke alarms should be provided in the buildings that are above 7.5 meters. This is also for the purposes of ensuring that the ASET is not limited by the effects that the fire as well as the building may have during the fire escape. A compartment wall should also be built along the corridors for the purposes of protecting the escape routes from the fire (Yao, et al, 2013). ASET and RSET may be affected incase the escape routes are not protected from the fire. The bedrooms should be enclosed by fire resistant construction. This is because the fire may break out at night making it difficult for the evacuation to take place. This factor should be considered during the design process. Analysis BS 7974 plays an important role in terms of providing guidelines that can be used for calculating the ASET and RSET. The Calculations plays an important role in promoting the safety of the occupants during a fire escape. It is also important to note that the calculations require several variables for the calculations to take place. The evacuation time is one of the aspects of both ASET and RSET. The evacuation time is usually symbolized by the  whose SI units is in minutes. It is also important to note that the evacuation term was first established in 1917 as the time for clearing the occupants of a building during a fire escape (Chow, 2013). In the exit design,  can be reduced by utilizing high flow rates. This has a direct impact on both the ASET and RSET. It is also important for the engineers to include inclusive designs so as to accommodate all the occupants in the building. The presence of an inclusive design plays an important role in ensuring that the evacuation time is reduced. The anticipated severity of the fire should also be considered during the design in order to ensure that the safety standards are enhanced. A building should also have the ability to resist the spread of fire and smoke in order to enhance the evacuation process. This is considering that the evacuation may be affected by various factors including the spread of the fire and smoke. An early warning system is also important in enhancing the evacuation time. RSET can also be considered as the time required for escape and it can be symbolized as. RSET has three main variables that are useful during the process of its calculation. This includes the perception time which is the perception to the time that the fire is perceived to exist. The perception time is usually represented as. Response time is considered as the time of recognition of the fire to the safety action and it is represented as. On the other hand, the elapsed time from the initiation of action to the time that the occupants reach a safe place is referred to as travel time which is represented as . RSET can therefore be considered as, = ++. It is however important to note that various factors may affect the flow at which the occupants during the fire escape. It is for the reason that a factor of safety should be considered during the design process. The perception time can be affected by various factors and it may be delayed for the people with hearing impairment (Guanquan & Jinhui, 2012). It is therefore important for the engineers to consider4 this factor during the design process. The engineers should ensure that fire alarms are both visual and audio. Balconies or flat roofs should be used during the escape as the stairs may be filled with smoke. The means of egress can be useful in terms of determining the RSET time. The RSET time can be lowered when there is an appropriate escape means in the building. An example in a calculation for RSET, in a four storey building on fire, the perception time  is 2 minutes, the response time to the safety action is 3 minutes and the travel time  is 4 minutes. The calculation for RSET = = ++ =2+3+4= 8 minutes Eight minutes may is fair for the process considering that the building is a four storey building. This is also considering that some of the factors that inhibit the flow of the occupants may lead to the delays during the process. It is also important to note that the les time taken during the process the better. A building should have the features that promote an easy evacuation of the occupants. ASET is also considered as the time available and it is represented by. When using the fire model, the length of time required for the occupants to carry out a safe egress after the alarm has been sounded is usually considered. The detection time is an important variable that is usually used during the calculations of ASET and it is usually represented by. The notification time is represented by. On the other hand, the onset of the hazardous condition is represented by. ASET can therefore be calculated by the summation of the variables. =++. According to BS 7974, the detection time is important as it plays an essential role in the tenability criteria. All the occupants in the building should be able to evacuated before ASET is reached. This is because once ASET has been reached, the conditions will be too harsh and none of the occupants may be able to evacuate the building. During the design of a building, it is recommended that ASET> RSET (Bjelland & Borg, 2013). The margin of safety which is represented by should be zero in order for the building to be safe. The marginal of safety is also an important factor during the design and it should be zero in order to ensure that all the occupants sin the building can be evacuated in safe condition without causing deaths or injuries. The safety index of the building should also be considered during the process of carrying out the design. An example for the calculation of ASET in a four storey building involves a detection time  of 2 minutes, a notification time  of 1 minute and onset of the hazardous condition  of 8 minutes. The calculation of ASET, =++. =2+1+8= 10 minutes. The higher the values of ASET, the better for the occupants of the building as they will have more time to evacuate from the building. The engineers should be focused on creating a design that will increase je values of ASET. The building characteristics as well as the features in the escape routes. The movement time is an important factor when dealing with RSET. Some of the delays may be caused by going through different doors. During the design process it is important for the engineers to consider this factor. The doors that are fitted at the escape routes should not have locks, latches or bolts. This is because it may reduce the movement time of the occupants. All the doors at the escape routes should not be locked but instead simple fastenings should be used. The presence of doors at the escape routes may also slow down the flow rates of the occupants contributing to injuries and deaths as ASET may be reached before all the occupants are evacuated. According to the principles of ASET, the visibility of the occupants during the escape must remain above 10 meters. The temperatures must also remain below Centigrade. This is because the conditions become untenable when the temperatures are higher. The concentration of carbon dioxide must also not exceed 1400ppm (Yao, et al, 2013). The engineers should consider these factors during the process of carrying out their design in order to promote the safety of the occupants during the fire escape. It is important for the engineers to ensure that all the escape routes have adequate lighting so as to ensure that the evacuation process is simplified. During the evacuation process, the occupants should not use the lifts as there is a danger of being trapped if the lift fails to work. This automatically results to death during ASET. Conclusion In conclusion, it is evident that the principles of ASET and RSET play an important role in the fire design. ASET is concerned with the time that the fire is ignited until when it becomes untenable. It is evident that the calculation of ASET requires various variables including the notification time, onset of the hazardous condition and the detection time. It is also evident that the various factors can increase the rate of ASET including the nature of the building and its design. It is for this reason that the fire safety design is important to the engineers. RSET is concerned with the time taken between the alarm time to the time the occupants have reached the exterior of the building or to a safety point. The design of the building may also make it difficult for the evacuation process to take place and hence increasing the RSET. It is evident that the ASET should be greater than that the RSET in order for the safe evacuation of the occupants of the building to be carried out. BS 7974 also plays an important role in defining the concepts of ASET and RSET during the design of the building. It is evident that the escape routes of the buildings should not hinder the movement of the occupants. List of References Bjelland, H., & Borg, A, 2013, On the use of scenario analysis in combination with prescriptive fire safety design requirements, Environment Systems & Decisions, 33(1), 33-42. Chow, W, 2013, Letter to the Editor: Comment on ‘RSET/ASET, a flawed concept for fire safety assessment’by V. Babrauskas, JM Fleming and BD Russell, Fire and Materials, Vol. 34, pp. 341–355 (2010), Fire and Materials, 37(3), 257-258. Guanquan, C., & Jinhui, W, 2012, Study on probability distribution of fire scenarios in risk assessment to emergency evacuation, Reliability Engineering & System Safety, 99, 24-32. Yao, W. et al. (2013). Fire risk mapping based assessment method applied in performance based design. Fire Safety Journal, 56, 81-89. Read More

It is usually impossible for the occupants to escape from the building after the conditions have become untenable. RSET is the required safe egress time and it is the amount of time from ignition that is required for the occupants to evacuate a building and to reach the building exterior or protected exit enclosure. Various factors may affect the RSET including the height and size of the building. RSET is also considered as the sum of the alarm time, the evacuation delay time and the movement time (Bjelland & Borg, 2013).

The alarm time is considered as the time that the occupants become aware of the fire through and automatic or manual fire alarm of the building. The evacuation delay is the time that elapses between the time the occupants are aware of the fire or after the alarm and the time that they decide to make the decision to evacuate. The pre-movement activities involve the time that the occupants investigate whether the fire is real, when they gather their belongings or when they start looking for their friends or family members.

Various factors may affect the pre-movement period including the nature of occupancy. The movement time is the time that the occupants reach the protected exit enclosure or the exterior of the building. The walking sped as well as the occupant flow rates affects the movement. This is considering that the occupants may have to pass through stairs, doors and corridors. The FDS-EVAC modeling can be used for the purposes of calculating the movement time. A factor of safety has to be applied during the calculation of RSET due to the uncertainties of the human behaviors.

During the design for fires safety, ASET/RSET concepts have to be considered. Different tools can be used during the process of calculating ASET and RSET. The provision of fire suppression system as well as providing an active or passive smoke control system may lower the ASET. The provision of adequate separation distances between the fuel packages can also play an essential role in ensuring that the ASET is increased. A customized fire protection and life system can be developed through the considering the different aspects of ASET and RSET (Chow, 2013).

The strategic placement of the smoke detectors can also play an essential role in dealing with RSET. A voice occupant notification can also be placed in different rooms for the purposes of ensuring that the occupants are able to know about the fire and its location or part of the building. This will play an essential role in reducing the pre-movement time. The pre-movement time is usually increased due to the lack of adequate information about the fire. On the other hand, it is also important to note that the presence of effective communication within the building is useful in reducing the pre-movement period.

Placing the exit signage in a building is also important in terms of reducing the movement. On the other hand, it is important to note that the proper arrangement of the means of egress can be useful in reducing the pinch points and excessive queuing which affects the movement. The consideration of fire safety can be useful in ensuring that the lives of are saved in the event of a fire. BS 7974 assumes that the provisions in the fire safety engineering strategy will be maintained and implemented throughout the life of the building.

This is considering that the risk of fire can occur at any time during the life of the building. Understanding the concepts of ASET and RSET is important in ensuring that the building characteristics do not support the fire but instead slows down the fire. During the design of a building, it is important to ensure that no room is used for the purposes of getting to the other. This is because of the difficulties that it may lead during the evacuation process. On the other hand RSET is also affected when the occupants have to pass through other rooms before they reach the exit.

Protected stairways together with additional smoke alarms should be provided in the buildings that are above 7.5 meters.

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