The Principle of ASET and RSET with Regards to Means of Escape - Coursework Example

Introduction In fire safety involves the prevention fire outbreak and mitigating the direct and consequential damages by ensuring that the fire is detected at early stages, reducing the spread of the fire by structural containment, provision of escape routes and being well equipped just in case of fire (British Standard 476: Part 7, 1997). When some occupants of a building which is on fire are exposed either to the product of combustion or to the fire itself for considerably a long time then the fire can be pronounced as being at dangerous level. When evaluating the level of safety that a building can be able to give to its occupants the usual practice is coming up with a quantitative performance practice. The quantitative approach comes in handy when it comes to comparing a number of strategies. RSET and ESET Recently there has been a metric has emerged that ignores the focus on accuracy as it considered to be a sensible concept. The principal behind the metric is that occupants of a building would require fixed time so to escape from the building which is on fire. The time required for occupants to make their way out the building is what is what is referred to as RSET (Required Safe Egress Time) while the time which is practically available is referred to as ASET (Available Safe Egress Time). In the case where ASET is greater than RSET the the building under consideration be considered as having passed the test of fire safety with regards to the occupants that are to escape from the building. The concept involves relatively simple calculations with the evaluation of the existing arithmetic relationships simple. The year 1975 saw RSET/ASET being put into use for the first time after being a study that was referred Indiana Dunes 1 which was sponsored by NIST (Bukowski et al. 1975). At the time the Indiana Dunes 1 study was being undertaken RSET/ASET had not yet put into use but evaluation of fire safety in the study the study was done by application of the concept though explicit nomenclature had not been established at this point. In the first phase on Indiana Dunes 1 study the time required for occupants of a building to escape was not put into consideration. The authors assumed that suppose there is anytime regardless of its exact amount after the fire alarm going off and before reaching untenable conditions in the escape route, then the assumption would be that success has been attained. Here it is assumed that no time is required for occupants make their escape to safety. Waterman who was one of the authors of Indiana Dunes 1 had the idea of having a more than zero time for escape in another follow up paper even though he did not give the analysis of the data (Waterman 1983, 25–50 ), but instead he borrowed the work of another author where there had been data analysis on the basis that it was necessary for building occupant to have a time of between 1 and 5 minutes to make their escape and on this basis Waterman settled for 3 minute as being an appropriate time. The 3 minutes that was chosen by Waterman could be considered a conservative figure when it is put into consideration that tests undertaken by Fire Department of Los Angeles had revealed that it was possible for occupants to escape in less than a minute for a staged exercise. Jonathan Sime, a human behavior specialist, produced a revised RSET scheme, whereby there was deviation from the earlier assumption that only reaction time to an alarm was needed by occupants then the occupant would move as a robot to exit point. Sime’s idea was that RSET was to be subdivided into three and this can be summarized by the expression RSET= Tr +Tc+Te. In the expression Tr is recognition phase, Tc represents coping phase ( that include fire fighting); Te represent the escape phase (which includes everything that happens thereafter an occupant manages to escape).conceptually the scheme passes as satisfactory whereby the defined times are able to carter for all the activities that transpire in a real fire situation. However, when it comes to actual practice, this scheme does not pass as being sound as it implies that specified fixed available time is satisfactory. There can be use of a method that is safety based that ensures a maximum escape time which is economically viable and physically deliverable. NFPA 101 Life Safety Code (2009) is also associated with the RSET/ASET scheme although it does not have wide application in single family housing. A guide has also been issued by Society of Fire Protection Engineers that puts into consideration human behavior in the application of RSET/ASET. In the guide there is reference to some studies where counterproductive activities are documented but SFPE has not recommended any allowance of time that can take care of such activities during calculation process. Distance of travel The distance an occupant is supposed to travel from a location in a room to another location that is considered safe is of vital importance and should not be omitted when addressing fire safety. The distance of travel is dependent on a room’s occupancy whereby some rooms are considered to be of higher risk in comparison to others with the speed of spread of fire being likely to be higher in these rooms and these calls for shorter maximum distance of travel to be assigned to these rooms (Communities and local Government, 2006). In applying the RSET/ASET scheme the existence of alternative escape routes needs to be put into consideration. The travel distances that assigned to a variety of premises are summarized in table 1 as given in Document B. Table 1 Use Alternative on the route of travel One alternative More than one alternative Office 18 45 Assembly (sitting in rows) 15 32 Industrial (Normal hazard) 25 45 Industrial (Higher hazard) 12 25 Storage (Normal hazard) 25 45 Storage (Higher hazard) 12 25 Sample calculations The parameters in the table 2 have been applied in the calculations. Table 2 Fire room name Area of room Ceiling height Door width Door height ROOM 1 144 2.2m .85m 2.1m ROOM2 284 2.9m .85m 2.3m ROOM3 33m2 2.9m 0.75m 2.3m ROOM4 15m2 2.9m 0.75m 2.3m ASET calculations The Available Safe Escape Time coincides with the smoke spill time from the room to the stair case. The equation to be used is In the equation Z = is the height of the door H= is ceiling height above the fire = growth time (=600sec for slow reaction) A = Area of the room = 0.937 Scenario 1 t=0.937. = 699.1s Scenario2 t=0.937. 734.4 s Scenario 3 t=0.937. 85.34s Scenario 4 t=0.937. 38s RSET Parameters The time of evacuation may be assessed by making use of the equation Where  represents pre-movement time which is assumed to be between 30 and 60seconds  is the time taken if one is walking time and is calculated using the equation On average the average walking speed is approximately about 1.2m/s . With the distance to be travelled the respective travelling time can be calculated and the results are as in table 3 below. Table 3 Scenario Distance Travelling time Scenario 1 9.7m 8.1s Scenario 2 11m 9.2s Scenario 3 9.8m 8.2s Scenario 4 5.5 4.6s t=  is the rate of flow through the doors with the specified door width by use of the equation =  Table 4 Scenario Door width Occupants Scenario 1 0.85m 64 57.9 Scenario 2 0.85m 57 51.5 Scenario 3 0.75m 33 33.8 Scenario 4 0.75m 3 3.1 By using equation The total evacuation time for the four scenarios will be Table 5 Scenario Time of evacuation Scenario 1 96 -126s Scenario 2 90.7-120.7s Scenario 3 72-102 s Scenario 4 37.7-67.7s Refugee area provision Since stairways provide relatively high level of safety during fire incidents, disabled people are exclusively allocated part of the stairways area called refugee area where are supposed to stay for sometime till they get further help so as to make it the area of safety (Kingspan, 2009). The area that has been recommended for refugee area is 900mm by 1400 which is big enough for wheel chair. In fire incidents it maybe possible that more than one disable could be on a floor but having a good fire strategy would ensure that only person will be waiting for help in the refugee area for each floor. Safety sign with inscription “Refugee-keep clear” need to be placed in the refugee area so as to ensure they are available for the disabled. There is also need for Emergency Voice Communication (EVC) to be installed to ensure smooth evacuation of disabled occupants of a building. The EVC system to be installed should adhere to BS 5839-9:2003 which there should be provision of type B outstations with communication links to a master station that is located at the fire alarm panel. Exit signs and lighting There should enough provision of lighting on all the exit routes in a building and the light are supposed to have separate circuits that is independent to the lines that are serving other parts of the building (British Standard 5266: Part 1: 2005) and the light installation need to conform to BS 5266-1:2005. Exit signs are a vital component of the exit and they should be striking of adequate size. The exit signs also are to conform to the requirement given in safety regulations of 1996. In RSET/ASET the fire resisting characteristics of each room is to be unique depending on the purpose of for which the room is supposed to serve. Rooms that serve as storage areas for combustible materials need to be constructed in a manner to guarantee a high fire resistance value. A person using a washing room may delay making exit when a fire incident happens and this makes it important for such rooms to be of high fire resistance. The escape routes in the building should be protected from fire to ensure safety when making escape. So as to comply with the requirement the corridors that are to be used as escape routes are constructed with highly fire resistant material in order to ensure there is no quick spread of fire. In RSET/ASET scheme the doors are supposed to play a role in reducing the rate at which the fire is able to spread. The door aspects which play a role in controlling the fire spread and the ease o making escape in the dimension of the door, the level of fire resistance the door can offer and the manner in which the door opens (British Standard 476: Part 22: 1987). The dimensions of the door are determined by the approximate number of occupants that are likely to use the door for escape during fire incidents. The fire resistance of the door is required to be close to that of the walls in which it is fixed. Doors which are on escape roots that serve more than 60 occupants need to have a design that allow opening in the direct of escaping occupants. The door should be fixed in a way that will allow opening with angle of at least 900 and the swing of the doors should be clear of floor level. The effective width should not in any way be reduced a cross a landing. Doors opening towards a corridor should have a recess that will prevent a swing that could encroach on effective width of stairways that they are serving. Doors on escape routes should not have locks, bolt fastenings or thatches. If need be there can be inclusion of simple fastenings on the doors whose operation is very simple and the operation if included should be at the side of approach of the people escaping. The fastening operation is supposed to be an easy task where there should be no need for using a key or any manipulation requirement that has more than one mechanism. In circumstances where there is need to have door operations that incorporate swipe combination or use of a proximity card, biometric data requirement, a code then it is a requirement that overriding of all these options should be possible when on occupant is approaching the door from inside the room that is being served by the door. Doors with such feature are found to be expensive and delicate and it may only be appropriate where the rooms they are to serve is for controlled use. Disabled Persons One characteristic of a good building design is its availability for use by by the disabled including those with visual problems and those with mobility ability problems this being in compliance Disability Discrimination Act (Safer Scotland, 2009). When evaluating a fire assessment there is need to consider explicitly the provision of escape means as well as provision of warning signs to occupants who may have any form disability be it sensory or mobility impairment. People with disability of any form should be able to receive fire alarm signals, and thereafter should be able to move out of the building safely without putting to jeopardy the safety of other occupants or should have way to the refuge area where they will stay awaiting their final evacuation from the building. In some type of building such as learning institutions some category of disabled occupants may have personalized evacuation plans which are put in place by Fire Safety Office working in conjunction with Safety, Health & Environmental Advisers. Some general matters require some special consideration and these includes the disabled occupants being given a chance of airing their opinion which serves to identify their needs and these will serve to well in making occupants and fire marshalls being aware of the need of the disabled. Another important thing with regards to disabled occupants is ensuring that the building has enough evaluation chairs placed in the escape routes and these chairs should suitable for use by the disabled. Conclusion In order for RSET/ASET to be successful there is need to have sound evacuation procedures and Fire Safety Plans. The issues that are addressed in fire evacuation procedures are : warning and evacuation signals, alerting fire safety department of the fire, the sequence of actions during the fire incident, evacuation procedure, management of crowd, the existence of a fire assembly for the building, evacuation of disabled and eventually re-admitting of people in the building where possible (Safer Scotland, 2009). A fire action is mandatory to be included in all buildings where there is concern for fire safety. During fire incidence it is important to ensure that there is enough number of fire marshals, security team and building staff this being very important in ensuring that nobody moves back to the building unless permitted. In overall this will serve in reduction of RSET at different locations in the building. It is very important that fire marshals, security team and building staff have some form of identification including wearing of badges, arm bands and they should also have access to facilities such as loud speakers as this will make it easy for them to provide the needed services in addition to keeping the crowds under control. Fire evacuation procedure for a building should be tested and a rehearsal done through undertaking drills which should be done at least once in a year as this important in ensuring that the building occupants are well aware of fire signals and routes they are supposed to follow during fire incidents. With such knowledge, building occupants will start evacuating from the building immediately the alarm goes off and they will in the required direction without panicking and these will reduce the RSET. Alarms are to be kept in good working conditions and these can be ascertained by the building manager undertaking test performance at least once in a week. In order to ensure there is fire safety in a building fire safety plan is required and this should be coordinate by a Safety, Health and Environmental section serving the building. A plan gives information such as results of assessment of fire risk and gives the occupancy of the building, the use the building is serving and the fire risk process. The building drawings are also made available with important information such as fire zones and levels of fire resistance, the location of alarm call points, location of fire doors and the detection devices. Rooms having high level fire hazard as well as assembly points should be marked on the building plans. As part of fire plans there should be inclusion all the fire incidences that have occurred as well as safety audits as this will go along way in improving fire safety levels. Other things that need to be recorded are the fire evacuation procedures, the list of people that should perform specific duties for fire safety as well as a summary of the remedies and defects that could have been identified during evacuation drills. Implementing the fire safety plan is usually a responsibility that is to be undertaken by Emergency Incident Manager. The building plans and fire assessment should be kept in the building and should be produced when required for inspection by fire safety authorities. References Bukowski RW, Waterman TE, Christian WJ. 1975 Detector sensitivity and siting requirement for dwellings. U.S.National Bureau of Standards, NBS-GCR-75-51, Gaithersburg, MD,. British Standard 476: Part 6: 1989 Fire tests on building materials and structures. Method of test for fire propagation for products. British Standard 476: Part 22: 1987 Fire tests on building materials and structures. Methods for determination of the fire-resistance of non-loadbearing elements of construction. British Standard 5266: Part 1: 2005 Emergency lighting. Code of practice for the emergency lighting of premises. (Superseded CP 1007 1955 A Code of Practice for Maintained Lighting in Cinemas Communities and local Government (2006).The Building Regulations 2000.Fire safety, Approved Document. Kingspan( 2009).The UK‟s approach to the thermal refurbishment of non-domestic buildings, Life Safety Code (NFPA 101). 2009 National Fire Protection Association, Quincy, MA. Safer Scotland (2009). Practical Fire Safety Guidance For Places Of Entertainment And Assembly. Scottish Government. Sime JD. 1986; 561–570. Perceived time available: the margin of safety in fires. Fire Safety Science—Proceedings of First International Symposium. Hemisphere: Washington D.C. Waterman TE. 1983; 25–50. Detector response vs. available escape time in residences. Proceedings of Applications of FireTechnology Workshop. Society of Fire Protection Engineers: Boston, MA,. Read More