Engineering Design Project: Required Safe Egress Time and Available Safe Egress Time - Assignment Example

RSET and ASET Recently there has been emergence of metric model that ignores focus on the level of accuracy with this concept being considered as being a sensible concept. The principal behind this model is that occupants in a building would require fixed time so to escape from a building on fire. The time required by occupants to escape from the building is what is what is referred to as RSET (Required Safe Egress Time) while ASET is which stands for (Available Safe Egress Time) is the time that is practically available for escape. For a case where we have ASET >RSET then the building under consideration will have passed the fire safety test regarding the building occupants that are to make their escape out of the building during a fire outbreak. This concept involves some calculations that are considered to be relatively simple where the evaluation in existing arithmetic relationship is simple. RSET/ASET was first put into use in 1975 after a study being conducted by Indiana Dunes 1 that was sponsored by NIST (Bukowski eat al. 1975). In Indiana Dunes 1 study time RSET/ASET was yet to be put into practical application but evaluation of fire safety in the study was done by applying the concept despite explicit nomenclature not being in place yet. In the first phase of the study the time of need for occupants to make their escape from a building was not considered. The assumption of the authors was that if anytime is available regardless of its amount after the sounding of a fire alarm and before untenable conditions are reached in escape route then it was assumed that there was success in escape. The assumption was that no time was necessary for occupants to make escape to safer grounds. One of the authors of the Indiana Dunes 1 saw the need of having some time allocation to carter for escape time and thus in a follow up paper without giving analysis of the data an instead borrowing another authors work that had analysis of data. On the basis that it was necessary for building occupants to have a time of 1 to 5 minutes to make their way out of the building and on the basis of this the Indiana Dunes 1 author chose 3 minutes as the appropriate that would be necessary for escape (Waterman 1983, 25–50 ). The three minute was a conservative figure putting into consideration the tests performed by Fire Department of Los Angeles that gave a figure of 1 minutes as being the required time in a staged exercise. A human behavior specialist named Jonathan Sime came up with a revised RSET scheme that deviated from the assumption that had been made earlier that it was only the reaction time to the alarm that was necessary for the occupants meaning that the occupants were o move like robots and escape. The idea of the human behavior psychologist was that RSET needed to have three components given by RSET= Tr +Tc+Te. In this expression Tr represents recognition phase, Tc is coping phase ( that include fire fighting); Te is the escape phase (which includes everything that happens thereafter an occupant manages to escape). These scheme conceptually passes to be a satisfactory one as the defined times are able to take care of all the activities that are likely to happen in a real fire situation. However, in actual practice, the scheme may not exhibit soundness as the implication is that specified fixed available time will be satisfactory. There can be application of a method which has a basis in safety and that gives maximum escape time and which is considered as being economically viable as well as physically deliverable. NFPA 101 Life Safety Code (2009) has been associated with the RSET/ASET scheme even although it lacks a wide application in single family housing. There is also a guide that has been issued by Society of Fire Protection Engineers that incorporates human behavior in applying the RSET/ASET. In this guide reference is made to some studies where there is documentation of some counterproductive activities but SFPE has not given any recommendation for any allowance of time which is to carter for such activities in the calculations. Distance of travel The distance the occupant of a building is expected to travel from a point in a room to another point that is safer is very importance and should always be considered in addressing fire safety. The appropriate maximum distance of travel depends on the occupancy of the room with some rooms being considered as pausing higher risk when compared to others and the speed of fire spread being likely to be higher in such rooms and thus calling shorter maximum distance of travel being assigned to these rooms (Communities and local Government, 2006). In the application of the RSET/ASET scheme one need to put into consideration the existence of alternative escape routes. The travel distances assignment in various premises are summarized in table 1 this being in accordance to 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 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 40x32=1280 12m .75m 2.1m 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 approximated at 1.2m/s .the longest distance to be travelled by the occupants on the ground floor are indicated on the plan in the appendix. These distances are equal and are given by Distance =  t=  is the rate of flow through the doors with the specified door width by use of the equation = = By using equation  (minimum)  (maximum) Exit signs and lighting It is important for enough lighting to be provided on the exit routes and the lights are to have separate electrical circuit from the lines that are serving other areas of the building (British Standard 5266: Part 1: 2005) with the light installation conforming to BS 5266-1:2005. Exit a very important component of the exit and they should be of adequate size. The exit signs are also to be in conformation with safety regulations of 1996. In both RSET and ASET the fire resisting characteristics for the room has to have some uniqueness that should be a reflection of the purpose to which the room will be put to. It is also important to a room serving as storage for materials that are combustible to be constructed in a way of guaranteeing a fire resistance value that is high. In RSET/ASET scheme the doors are to serve in reduction of the rate of spread of fire. The width and height, the fire resistance of the door and the manner of opening of the door are the door aspects that are of help in control of the fire spread (British Standard 476: Part 22: 1987). The determination of the door width is determined the number of people that are to use the door in escaping in incidents of fire. The fire resistance of the exit door is to be close to that of walls in it is fixed. Doors located on escape routes serving more than 60 occupants should have a design having a design allowing opening in direction of escaping occupants. The fixing of the door is to be in a way that allow open with an angle 900 with the swing of the door being clear of floor level and in no way is effective width is to be reduced a cross landing. Doors that are to open into a corridor are to have a recess that prevents swinging that is likely to encroach on effective width of stairways they are serving. 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 Conclusion For effectiveness to be realized in RSET/ASET it is important to have sound evacuation procedures accompanied by good Fire Safety Plans. The aspects that are looked at in fire evacuation procedures are : warning and evacuation signals, alerting of fire safety department about the fire, the sequence of actions to be undertaken in the fire incident, procedure of evacuation, crowd management, fire assembly existence for the building, evacuation of those who are disabled and eventual re-admission of people in the building where this is possible (Safer Scotland, 2009). A fire action is a mandatory inclusion in all buildings where there is fire safety concern. In event of fire there should be enough fire marshals, security team and building staff as this is recognized as a very important step of ensuring that nobody can move back into the building unless otherwise permitted. Overall this will bring about reduction of RSET for different locations in the building. It is of importance for fire marshals, building staff and security team to have identification of some sort that could be in form of badges, arm bands and also having access to facilities such as the load speakers as this will make it easy for them in providing the required services and keeping the crowd under control. It is also important to have a rehearsal of fire evacuation procedure by drills being undertaken at least once in a year so as to ensure that occupants of a building will be aware of the fire signals and for complex building the route they are supposed to take in their way to safety. Having such prior knowledge the building occupants will be in a position to evacuate immediately alarm is raised and they will be moving in the right direction with no any form of panic and thus reducing RSET. It is to be ensured that the alarms are in good working order and these can be achieved by having the building manager undertaking test performance once a week at minimum. For ensuring fire safety in the building a fire safety plan is to be in place and it should be under the coordination of a Safety, Health and Environmental section of the building. A plan will give information that will include results of assessment of fire risk and will give the number of occupancy of the building, the use the building and the fire risk process. The building drawings are also to be made available where information such as fire zones and fire resistance levels, the location of alarm call points, location of fire doors and the detection devices. Rooms that have high level fire hazard as well as assembly points are to be marked on the building plans. As part of fire plans all the fire incidences that could have occurred as well as safety audits are to be included as this will result to improvement in fire safety levels. Other things that are to be recorded are the fire evacuation procedures, the list of people that are to perform some specific duties for fire safety as well as a summary of the remedies and defects that may have been noted in the evacuation drills. Implementation of the fire safety plan usually a responsibility that is to be undertaken by Emergency Incident Manager. The building plans and fire assessment is to be kept in the building and is to 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 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. 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,. Appendix 1 Read More

A human behavior specialist named Jonathan Sime came up with a revised RSET scheme that deviated from the assumption that had been made earlier that it was only the reaction time to the alarm that was necessary for the occupants meaning that the occupants were o move like robots and escape. The idea of the human behavior psychologist was that RSET needed to have three components given by RSET= Tr +Tc+Te. In this expression Tr represents recognition phase, Tc is coping phase ( that include fire fighting); Te is the escape phase (which includes everything that happens thereafter an occupant manages to escape).

These scheme conceptually passes to be a satisfactory one as the defined times are able to take care of all the activities that are likely to happen in a real fire situation. However, in actual practice, the scheme may not exhibit soundness as the implication is that specified fixed available time will be satisfactory. There can be application of a method which has a basis in safety and that gives maximum escape time and which is considered as being economically viable as well as physically deliverable.

NFPA 101 Life Safety Code (2009) has been associated with the RSET/ASET scheme even although it lacks a wide application in single family housing. There is also a guide that has been issued by Society of Fire Protection Engineers that incorporates human behavior in applying the RSET/ASET. In this guide reference is made to some studies where there is documentation of some counterproductive activities but SFPE has not given any recommendation for any allowance of time which is to carter for such activities in the calculations.

Distance of travel The distance the occupant of a building is expected to travel from a point in a room to another point that is safer is very importance and should always be considered in addressing fire safety. The appropriate maximum distance of travel depends on the occupancy of the room with some rooms being considered as pausing higher risk when compared to others and the speed of fire spread being likely to be higher in such rooms and thus calling shorter maximum distance of travel being assigned to these rooms (Communities and local Government, 2006).

In the application of the RSET/ASET scheme one need to put into consideration the existence of alternative escape routes. The travel distances assignment in various premises are summarized in table 1 this being in accordance to 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 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 40x32=1280 12m .75m 2.1m 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 approximated at 1.2m/s .the longest distance to be travelled by the occupants on the ground floor are indicated on the plan in the appendix.

These distances are equal and are given by Distance =  t=  is the rate of flow through the doors with the specified door width by use of the equation = = By using equation  (minimum)  (maximum) Exit signs and lighting It is important for enough lighting to be provided on the exit routes and the lights are to have separate electrical circuit from the lines that are serving other areas of the building (British Standard 5266: Part 1: 2005) with the light installation conforming to BS 5266-1:2005.

Exit a very important component of the exit and they should be of adequate size. The exit signs are also to be in conformation with safety regulations of 1996.

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