Means of Escape from Residential Dwellings - Term Paper Example

MEANS OF ESCAPE FROM RESIDENTIAL DWELLINGS ABSTRACT This report focuses on the standard recommendations for means of escape from residential dwellings. Charm House will extensively be used as a study case in comparing with a performance based assessment. The report will in specific address the fundamental standards that are worth implementing to ensure that there are clear routes of escape from residential dwellings. The existing laws in force in relation to the evacuation routes in residential buildings will be deemed to apply at all levels of their design. Fateful events are bound to happen but the uncertainty holds as to when the event will materialize. Measures should thus be put in force to mitigate the magnitude of loss should the event occur. The report uses the ASET-RSET to check the performance based design of the house with regard to escape routes during life threatening occurrences like fire or unexpected flooding and the evacuation processes in such instances. INTRODUCTION There is a general desire that all residential dwellings should meet the minimum requirements for risk management. Residential buildings differ in many aspects ranging from type to occupancy. This means, therefore that there can never be any one means of escape that can be used as a standard for the other houses. There are; however, specific guidelines that are established to meet the needs of escape from any particular building. These rules and regulations need to be reviewed occasionally in order to minimize evacuation time in any one occurrence. The main risk facing Charm House is fire. This report, therefore, will address the means of escape from Charm House in the event of fire. FEATURES OF DESIGNED CHARM HOUSE Charm House is a huge building that comprises of a number of bedrooms, sitting areas, bathrooms and kitchen. It also has an underground building and a garage. Out rightly, this building hosts a number of people and a great value of asset base. It is therefore, possible that in the event of fire there can be a great commotion as occupants struggle to vacate the house. This creates the need to ensure the building has adequate means of escape. The design of this house has been done in such a way that evacuation process is fast enough as to eliminate any risk of loss of life and maximize salvage. The building has a number of doors both from the front and at the back. There are also a number of windows from all sides of the building and stairs. The various means of escape should meet these conditions: The windows are easily accessible to apparatus for rescue Both the door and the window should open to the exterior balcony The window should be large enough ( about 6,1 meters) The source of specific fire can be determined by the FDS and CFAST models. Application of these models in the time calculations helps in designing the routes of escape in a residential dwelling. IMPROVEMENT In the event of fire, there are two main causes of risk of loss of life: shocking and poor visibility. This is purely as a result of smoke and carbon monoxide gas. This gas is highly toxic and kills fast. It results from insufficient combustion of carbon content due to low supply of oxygen. This can be addressed by ensuring that the building is well ventilated. Apart from leaving the windows open, the house should also have some other ventilation. The location of the garage is another hazard of a fire peril. The oil rags and other petroleum products usually found in the garage form combustible products that can accelerate the levels of fire. Limiting combustibles, maintaining adequate distance between living rooms and hazard packages and provision of control systems for smoke are some of the ways of increasing the ASET. On the other hand RSET can be increased by placing smoke detectors in a strategic location where it can easily be noticed by the occupants. Egress means should be arranged intelligently (placement of exit signs) to preclude unnecessary queuing, pinch points and thus reduce movement time. RSET ESTIMATION The “Required Safe Egress Time” (RSET) refers to the overall time taken during the evacuation process. It is measured from the time the fire ignited up to the time the occupants vacate and reach the outside of the building or some other protected enclosure. Alarm time and ‘evacuation delay’ time are crucial in RSET estimation. Alarm time refers to the time taken for the occupant to note there is fire through any occupant notification means. ‘Evacuation delay’ time (pre-movement time) refers to the time lapse from the time the fire alarm was noticed to the time evacuation starts. Pre-movement time is largely determined by the occupancy type of the building. It can take long in residential building and especially so during the night. The time taken for the occupants to come out of the building (or a protected exit enclosure) is the movement time. It is calculated by considering the occupants’ walking speed and the rates of flow through elements of egress like the stairs, corridors, doors or application of evacuation modeling like FDS-CFAST. Human behavior is however unpredictable and therefore, a safety factor should be applied to this time before the estimation of RSET. In general RSET can be estimated by applying this formula: RSET = t alarm + t movement + t pre-movement Where; t alarm = time taken to detect an alarm; utmost 10s t movement = movement time – from evacuation model or empirical formula; the average distance to the exit/ average escape speed = 18/0.15 = 120s t pre-movement = pre-movement time, that is, the time of recognition and response = 80s Therefore, RSET = 10 + 120 + 80 = 210s ASET CALCULATION The “Available Safe Egress Time” (ASET) refers to the total time that passes from the time fire ignited to the time untenable conditions are developed. It is generally determined through the application of fire modeling or the empirical correlations. This is done by first establishing a design fire or rather the history of the rate of heat release from the house. This is achieved by considering the various combustibles and related products yield that are within the building. Secondly, a fire model is made to establish the time taken to cause the space untenable as a result of poor visibility due to smoke or excessive heat. This should then be compared with pre-set criteria for tenability. This may be Maintaining visibility of 1.6 meters and above Temperatures must not exceed 800c Concentration of carbon monoxide must not exceed 880ppm. Temperature beyond 800c is injurious to a person and it will be above 800c at 1.6m in 220s. Carbon monoxide reaches 880ppm in 280s. From these calculations, the ASET will be 220s through FDS simulation. COMMENT Acceptance of a design should depend on whether the ASET is bigger than the RSET having put into consideration the necessary safety factors. A design approach should neither be too conservative nor too optimistic. Therefore, any smoke encounter within the building should not be treated as system failure and occupants should not be presumed to have perfect knowledge leading to anticipation and subsequent avoidance of smoke movements. Furthermore, the results emanate from the basis that occupants are escaping. However, it should not rule out the chances of occupants escaping through smoke and the likelihood of fire fighters rescuing others. This determination will definitely increase the ASET. RECOMMENDATIONS This report recommends that Charm House use window panes to fit the windows and not use grills so that in the event of fire some persons can easily break the window pane and get out through the window. This enhances the evacuation process as there is tendency of the occupants struggling to get out through the door and this increases commotion hence slowing down the evacuation process. It is also recommended that there be an assembly point where all people evacuated from the building meet. This ensures that there is nobody left inside the building before any further step to salvage from the fire. It is recommended that Charm House use UV flame detectors as it is highly sensitive thus a boost to the time taken to detect some fire within the building. A life voice notification system for the occupant should be used to reduce uncalculated moves during the evacuation process as sign language can be hindered by the presence of smoke. Notice that the occupants will make independent exit choices meaning that door usage will not be proportional and some doors will not be used optimally. This lengthens evacuation time. CONCLUSION This report has addressed the means of escape from residential dwellings. Charm House was used as a case study, however, the concepts hold for any other type of building. A design fire and modeling techniques have been highlighted with specific emphasis to the FDS and the CFAST techniques. The values obtained offer a great assistance in the design of means of escape from residential building with greater emphasis on the event of a fire and the escape routes during the evacuation process. The recommendations in this report majorly focused on the improvement of the initial design of Charm House in a bid to eliminate the risk of loss of life and also maximize the salvage should a fire operate. RSET estimation and ASET calculation have also been shown. References Canadian Wood Council (CWC), (2000), Fire safety in Residential Buildings,Building performance bulletin, series 2 Silcock, G. (1987), “Buildings and Fire, Longman Scientific & Technical”, New York Vicsek T. (2000). “Simulating dynamical features of escape panic”, Nature. 407: 487-490. Read More