Fire Engineering and Prescriptive Approaches in Design of the Means of Escape in Building in the UK - Report Example

Critical review of the principle of ASET Student Name Professor’s Name Course Date Outline I Introduction II The requirement of B1 of the Building Regulations III A review of the principle of ASET RSET and how it is incorporated in to standard UK guidance IV Example calculations V Discussion, Analysis and Conclusions References Introduction Potential users and occupiers of building are put in strange situation when fire outbreaks that is they are confused because their life is threatened. It is the responsibility of the owner of the company to ensure that their building adhered to safety measures relating to escape means during fire outbreak. The engineers and architects should ensure building they design and construct minimise possibility of deaths during fire outbreak, as there have been numerous fire outbreaks causing injuries and deaths. Besides, the common man should have some information to detect the fire outbreak in order to prevent the possibility of a major fire explosion that could engulf the area. This means that the number of users, purposes of building, distance covered in building and height of the building plays an important role in designing escape route. In the rest of this report first the requirement of B1 of the Building Regulations of the talk will be discussed. In the following section the principle of ASET RSET and how it is incorporated in to standard UK guidance will be discussed and an example calculation has been done. Then there will be a discussion, analysis and conclusions of the means of escape. The requirement of B1 of the Building Regulations B1 of the Building Regulations require buildings to have the means of escape, easy access to the building and evacuation strategy. The requirement of B1 of building regulation for means of escape states that a building should have appropriate warnings of fire outbreak as well as enough space for people to escape from the building. This done before construction of the house begun that is design stage. If it is not followed during construction the means of escape from the building will be difficulty. For this reason it is the responsibility of the owner of the building to design escape routes that accommodate the number expected in the building in case there is fire. This will help in preventing excessive lose of lives. It is required that a building should have a wide travel space which will enable both familiar and non-familiar occupants of a building to escape from fire. The doors should be wide. The door ways of a building should be labelled with proper colours or signs that indicate the escape routes in case of fire. More so, before constructing a house, the risk profile of resident is taken into consideration, that is, the escape or evacuation of a week occupants is different from sleeping occupants(Chow, Fong, Pang, Lau and Kong, 2006). The principles laid down for fire design requires the owners of include alternatives means of escape during the design process of the building. For tall buildings where an individual can not reach area of safety quickly stairs should provided that are of relatively safe for escape. This stairs should be protected, be of reasonable distance and be within the exit route. However all these will depend on the size of the building, the riskiness of the building to have fire, the height of the building and expected number of people in the building. The escape routes should have sufficient lighting to enable the escapee to see the safety route to use; it should also have means of smoke control and alarm system to alert users of the house of the fire outbreak. Make provisions for fire escape routes to the occupants of the buildings giving room for many clearly marked exit routes in the high rise buildings because they carry many occupants at any given time as compared to the single storey building. It is required that a building should have a wide travel space which will enable both familiar and non-familiar occupants of a building to escape from fire. The doors should be wide. There should be ideal heating and ventilation in the building to enable proper circulation of air and temperature. The door ways of a building should be labelled with proper colours or signs that indicate the escape routes in case of fire. Windows that are expected to be used for emergency cases should have minimum 0.33m2 area that can be wide open which is 4.5m from the ground. The window should be an open place that is safe from fire, however if the escape route is another room then the room should be have an access to safety area(Chow, 2006). This means the escape room should have more than one door for escape. For tall buildings there should be flat roofing for escape lead to a route across the roof should lead to a storey exit which is 30 minutes fire resistance or external escape route. A review of the principle of ASET RSET and how it is incorporated in to standard UK guidance This principle plays an important role in guiding engineers and architects in designing safety measures for buildings. This has been well documented in UK standards that are applicable. According to the standard safe egress time is the time taken by fire to cause unsustainable conditions by human beings from time the fire breaks. The principle gives guidelines for means escape design based on their types and occupants. It ensures that there is proper layout for escapes routes and fire and smoke management in these routes. However when designing it should be put in mind that people will always consider familiar routes and exits in case an emergency thus this will impact their ability to escape(McGlennon, Montgomery and Turner, ,2009). The factors that are considers in determining the time of evacuation or escape which include level of alertness, number of people in the house, mobility, mental tolerance, role and responsibility and level of education. The figure below shows time taken by humans in responding to emergencies (BS7974: 2001) People learn about the fire when hearing an alarm and smoke or flame or even or reactions of other people are called recognition time. This is estimated using the following formulae that is recommended by BS 7974 RSET=++(+) Where is time taken to detect fire from the time it started while is the time take to raise an alarm from the time of detection. (+) presents the time occupants of building to move to safety. Separately they present pre-movement time and travel time. This time will be determined place of safety as designed by engineers. In the calculation of this time various things are taken into account like dead-ends, overcrowded areas, travelling time of people into and out of building. Available safe escape time is time available to occupants to escape from the building. The main differences between required safe egress and Available safe escape time will determine whether will have causalities’ in case the fire breaks out. When the Available safe escape time is greater than required safe egress there will greater casualties this will require redesigning the escape routes according to the standard(The Fire Strategy Company, 2008). To have a proper design ASET and RSET differences will be used as a criterion for safety measure. However these values will have to be approved by relevant authorities before the construction of the house continues. Looking at the formula RSET=++ (+) that is used, it can be noted that if is very large will mean that evacuation will take a longer period thus increasing the possibility of having casualties. This value is determined by the response of users of the building while their responses to fire will be determined by their psychological and physical conditions at the time of fire outbreak. For example when one is a sleep, naked and poor healthy will react differently as compared to when alert, awake and dressed, knowing of fire protection devices in the building and intensity of fire. Some of the people will react to fire alarm in a negative way that they will start collecting important documents or valuables while others may decide to start looting while others are escaping. Thus it is important for one to consider cognitive functioning ability of the users of the building before estimating. Most will need to gather further information before beginning to evacuate from the building through phone calls, warnings from neighbours and management before evacuating. After estimating one needs to estimate which is time taken to travel to within the building as one is escaping. This time is determined by gender, population of the occupants, age and health of occupants. Example calculations The risk is estimated as: Risk = Sum of Probabilities x Consequences Consequences include delaying of people due to walking speed and visibility/optical density, harmed , incapacitated by smoke or heat. This can be quantified using quality of life index, ALARP, mortality rates or lost-life-years. Sum of probabilities are estimated using Probabilistic reliability analysis. This is done as State function: z(x) = tASET – tRSET Failure domain: Ωf ≡ z(x) ≤ 0 “Design” point : z(x) = 0 x is a vector of uncertain parameters that is travelling time, Pre-movement time, occupants density, smoke and heat release tASET : complex and “expensive” numerical fire simulation (CFD) tRSET : complex evacuation simulation + additional Δt‘s Calculated pfs per hostile fire Results “per hostile fire” WITH and WITHOUT Detection & Alarm System Results “per hostile fire” considering the previous event tree and 10% failure Visibility: 0.9 x 0.2142 + 0.1 x 0.6819 = 0.2610 FED: 0.9 x 0.0174 + 0.1 x 0.0540 = 0.0211 Results per annum Visibility: 0.0013 per annum (compare to 0.0034) FED: 0.000105 per annum (compare to 0.0003) Discussion, Analysis and Conclusions The means of escape in building in UK are designed using fire engineering as well as prescriptive approaches. The engineers and architects usually are required to follow laid down standards governing construction industry in UK and this are approved by the authority construction begins. The escape routes in most buildings in UK are regulated in BS7974, approved document B, and BS9999. This standards requires fire escape means to be designed in a manner that ensures smoke does not spread across the route and choke occupants escaping. They require a building should have a wide travel space which will enable both familiar and non-familiar occupants of a building to escape from fire. The doors should be wide and should be labelled with proper colours or signs that indicate the escape routes in case of fire. This three standards govern the way building are designed in the UK especially the escape routes from dwelling houses to offices. BS9999 provides figures of population expected in various buildings and how stairs should be designed for such densities. It recommends some stairs to have staircases with sprinklers while for some building are not required to have them, it also recommends staircase width and travel distance. Approved document B states that evacuation time should not exit 2.5 minutes for each storey for safety purposes to safety areas such as escape stairs. It further recommends that for protection of the building and escape route using suitable non-combustible materials which possess a specified fire resistance period for different construction elements and resisting the action of fire are described. It also provides that stability, integrity and insulation of the exit stairs or routes are of paramount important. Any architects who follow this standard are assumed to provide enough protection to occupants of buildings while those who try to ignore are asked to repeat their work the relevant authorities. The standards do not provide interrogation by designers or architects on the ability of the escape means ability to help users escape considering various factors including building features. Some building will not use prescribed means of escape with approval from relevant authority because of the special features that it may posses in this case fire engineering approach is used where there are no standard figures for the design of escape route but what is determined from simulation and in this case timeline approach to estimate the evacuation time of the building occupants becomes very important. For example elderly or under age children houses or homes, prescribed designs may not follow because of the special needs of the people. This case fire modelling is used to determine the type of escape route to be designed. Such homes or houses will require houses with one floor that have exit routes that are more than 2.5 m exit routes but simulation should provide direction. If the floor is estimated to have 52 people simulation will base the response time on randomly distributed mean of value equal to 1.5 min/s. for the children or elderly the evacuation time will be 150 s while young and energetic young men will be 52s. References BS 7974, 2001. Application of Fire Safety Engineering Principles to the Design of Buildings - Code of Practice, British Standards Institute, UK. Chow, W.K., Fong, N.K. Pang, E, Lau, F. & Kong, K., 2006. Case Study for Performance-Based Design in Hong Kong. Paper presented at Society of Fire Protection Engineers – 6th International Conference on Performance-Based Codes and Fire Safety Design Methods on 14-16 June 2006 by Professor W.K. Chow Chow, W.K., 2006. “Fire engineering approach and discussion on the design fire,” 6th International Conference on Performance-Based Codes on Fire Safety Design Methods, June 14-16, 2006, Tokyo, Japan – Paper to presented, June, 2006. Dowling, J. & Brian Kirby, B., 2009. Fire protection- BS 9999: A new approach to design of fire precautions in buildings. [ Accessed on 25th January, 2013] FSH/24 (2001). Application of fire safety engineering principles to the design of buildings - Code of practice. London: BSI Government of Ireland, 2006. Building Regulations 2006- Fire Safety. Dublin: Stationery Office McGlennon, M., Montgomery, S. & Turner, B.,2009. Promoting Safe Egress and Evacuation for People with Disabilities. National Disability Authority The Fire Strategy Company, 2008. A Guide to BS 9999:2008- Code of practice for fire safety in the design, management and use of buildings. [ Accessed on 25th January, 2013] Read More