Fire Engineering Strategies - Term Paper Example

Fire engineering strategies xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Name xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Course xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Lecturer xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Date Table of Contents Table of Contents 2 1.0 Introduction 2 2.0 Fire alarm and detection systems 3 2.1 Requirements for smoke alarms in dwellinghouses 6 3.0 Fire alarm and detection systems in non-residential buildings 7 4.0 Building occupancy, purpose groups 8 5.0 Horizontal and vertical escape route 8 5.1 Travel distance and exit width 9 5.2 Stair provisions 10 6.0 Conclusion 10 References 11 1.0 Introduction Protection of health and safety of the general population takes centre stage in government activities. Governments have therefore drawn up rules, regulations and laws for the constructed environment. In line with this, regulation procedures and technical requirements have been formulated in laws in order to check if building plans comply with the laws. Building permits are only issued if the building plan meets all the requirements. In Britain, construction of buildings is guided by the British Standard Regulations which contains the Building regulations among other regulations. This regulation contains five parts which are designated B1, B2, B3, B4 and B5 (Billington et al 2007). This report will focus on Schedule 1 of Part B (B1) which is concerned with means of warning and escape from buildings, access to fire fighting services and fire spread inside and outside buildings. The aim of this regulation is to ensure that buildings are constructed in such a way that ensures occupant’s safety as well as the safety of those living around the building. It should also provide maximum assistance to fire fighters. The report will critically discuss and analyze functional requirements of part B1 of the Building Regulations under the subheadings; fire detection and alarm systems, building occupancy, purpose groups and horizontal and vertical escape route design principles. 2.0 Fire alarm and detection systems The Building Regulations 2000 states that Buildings should meet the following requirements in the event of a fire; a) Occupants shall be warned sufficiently and be able to arrive at safer place within the shortest time possible. b) The building should by all means resist instant collapse in order to give occupants sufficient time to evacuate and prevent rapid fire spread. c) The building should ensure minimum spread of fire within and outside the building. d) Fire facilities and appliances should be accessible to fire fighters in their efforts of stopping the fire and saving of lives. The first requirement in the building regulations is met by providing sufficient means of warning and adequate number of protected escape routes and exits. The second requirement is met by ensuring that structural elements such as roofs, floors, frames and load bearing walls are set in accordance to fire resistance standards. The third is met by compartmentalizing large buildings and setting fire resistance standards for floors and walls bounding each compartment. The third requirement is also met by constructing surface linings of ceilings, roof coverings, internal and external walls in a way that inhibits fire spread. The forth requirement of this regulation is met by providing access to fire mains, firefighting personnel, fire appliances within the building. Making sure that smoke and heat may are expelled from the basement is another way of meeting the forth requirement (Office of the Deputy Prime Minister 2000). However, it is difficult to apply these requirements of the Approved Document (AD) B to large and complex facilities such as airport terminals. In such a case, satisfactory fire safety standards can only be achieved by applying the fire safety engineering approach which provides a holistic fire safety package. This approach is also commonly used in solving problems of building designs. Fire detection and alarm systems are automatic systems installed in buildings to alert and warn occupants of fire. The B1 document provides three main options for residential houses also referred to as dwellinghouses. The first one is to have an automatic alarm and fire detection system as par the recommendations of BS 5839 Alarm and detection system for buildings, part 1: 1988 Code of practice for system design, installation and servicing. The second option is an automatic alarm and detection system in accordance with the recommendations of the BS 5839 Fire detection and alarm systems in buildings, part 6: 1995 code of practice for the design and installation of fire detection and alarm systems to at least a Grade E type Ld3 standard (Office of the Deputy Prime Minister 2000). The third option is to have an adequate number of smoke alarms. Installation of the smoke alarms differs depending on the kind of building; Large dwellinghouses: AD B1 describes a large dwelling house as one having one or more floors with an area greater than 200m2. The regulation recommends installation of L2 system into such a building as described in part 1 of the BS 5839. In this case, provisions in clause 16.5 concerning stand by supply duration may be disregarded. AD B1 also recommends that if the system is unsupervised, the system should be automatically maintained by the standby supply within 72 hours of operation. A large house which is less than three storeys may be fitted with Grade B type LD3 fire detection and alarm system and installed in accordance with BS 5839: Part 6 rather than the L2 system which is mainly used for buildings more than three storeys. Loft conversion: In the case of loft conversions where a loft space in a one or two storey residential house is converted to a habitable accommodation, an automatic alarm system and smoke detection should be installed throughout the entire building and not just the extended part. Installation is guided by the principles described above depending on the size of the house, either two or three storey house. Sheltered housing: Sheltered housing forms a group of dwelling houses designed specifically for people with special needs or require special assistance for instance the elderly. Each accommodation unit will have common amenities such as communal lounges in addition to other common facilities like sanitary and cooking facilities. BS 5839 Part 6 proposes installation of a Grade C, Type LD 3 system into such buildings. The detection equipment should be directly connected to a central lay station or monitoring point so that the supervisor or warden can easily locate the house that is on fire. Flats and maisonettes: Principles of provision and installation of fire detection and alarm system in flats and masionettes are similar to those of dwellinghouses. However, the systems installed in individual flats need not be interconnected. Student residential accommodation: Halls of student’s residence where study bedrooms are owned by individuals and have shared washing facilities and dining should have general evacuation similar to that designed for non-residential buildings. Automatic detection systems should be installed in each flat which has its own entrance door. Therefore, warning will be given by the automatic detection system of the flat of fire origin. 2.1 Requirements for smoke alarms in dwellinghouses Smoke alarms should be designed, manufactured and mains-operated in accordance with BS 5446 Components of automatic fire alarm systems for residential premises, part 1: 1990 Specification for self-contained smoke alarms and point-type detectors. They may contain a power supply that is secondary for instance a replaceable or rechargeable battery or capacitor. Part 1 is concerned with optical smoke detectors (photoelectric) and ionization chamber smoke detectors. These different types of detectors respond differently to fast flaming fires and smoldering. Therefore, the most appropriate location for installation of optical smoke alarms would be in circulation spaces like landings and hallways while ionization chamber smoke alarms are best placed in places where the fire poses the greatest danger to occupants such as living rooms. In addition, optical smoke detectors tend to be less sensitive to low levels of smoke thus they are less likely to cause false alarms. Smoke alarms should also be installed in circulation areas, that is, areas between sleeping places and places of potential origin of fire such as kitchens and dining rooms. They should be about 7.5m from the doors to all habitable rooms surrounding them. They should be at least 300mm from light fittings and walls and should be fixed to the ceiling. The position in which the smoke alarm is fixed should allow for regular testing, cleaning and maintenance. Besides that, the alarm should be located away from objects that produce fumes, steam or condensation so as to minimize incidences of false alarms. Such objects include bathrooms, air-conditioning outlets, heaters and cooking areas. The location should neither be too hot nor too cold in comparison to the rest of the house as such would create air currents which would carry smoke away from the unit. 3.0 Fire alarm and detection systems in non-residential buildings Installation of the systems into such buildings depends on the escape strategy applied. The three escape strategies used are simultaneous evacuation where all occupants leave at the same time, phased evacuation where occupants in the affected floor are immediately evacuated followed by the others in other floors and progressive horizontal evacuation where affected occupants are moved to safe places within the building and later on evacuated completely from the building if need arises. Fire detection in buildings other than dwellinghouses may not be necessarily complex since occupants are always alert and may detect fire through observation or smell. However, several fire safety measures need to be incorporated in the building. These include sounders that are manually operated such as hand bells and rotary gongs as well as manually operated simple call points combined with charger, battery and bell. A fire warning system that is electrically operated and connected to a call point could also be installed in the building and should comply with BS 5839: Part 1. Other fire alarm and detection systems recommended in BS 5839: Part 1 include types L, m, P and X, types L1, 2 and 3 and types P 1 and 2 (Communities and local Government 2007). 4.0 Building occupancy, purpose groups In order to design the most appropriate means of escape, it is important to determine the average number of people who are likely to be in the building at any given time. This is known as occupancy capacity and depends partly on purpose groups and partly on the total number of people intended to occupy the building. Occupant capacity is important in assessing the number and width of storeys, exits from rooms, final exits and escape stairs. Occupant capacity for some buildings such as restaurants and theatres is quite easy since it is calculated by adding the number of seats and staff allowance. However, it is difficult to calculate occupancy capacity for buildings that contain supermarkets, banking halls, shops and other outlets where clients are served while standing. In such a case, the designer will use table 1 of AD B1 which gives the value of occupant capacity based on floor space factors (in m2 per person) divided into the relevant area of the floor (Sheridan et al 2003). 5.0 Horizontal and vertical escape route Evacuation from a building can be done into four distinct phases: Phase 1: Evacuation from the origin of fire Phase 2: Evacuation to a relatively safe place Phase 3: Evacuation of a section of the building Phase 4: Evacuation of the entire building Phase 1 and 2 are termed as the horizontal escape routes as they involve moving away from immediate danger and effect of the fire. Phase 3 and 4 on the other hand, involve horizontal and vertical movement. Vertical movement is with regard to upper storeys and it is by way of stairways to safer places in the building or away from the building. 5.1 Travel distance and exit width Travel distance is a component of horizontal escape routes. It is the actual distance that a person travels from any point in the storey to the nearest floor exit. It is measured along the most direct and shortest route. Therefore, when designing a building, it is important to take into consideration floor layout in terms of partitions, walls and fittings. Exit width is the width of an escape route which could be the room, the corridors and the stairways. This width should be adequate enough to permit planned evacuation processes and normally should not fall below 900mm for doors and 1150 for escape corridor width (Billington et al 2007).exit width depends on a number of factors including ‘flow time’, rate of flow and the number of occupants. Width of exit is normally expressed by the formula; U= N/ (40 × T) where: - U = number of units required N=number of occupants 40= standard rate flow-constant T= Flow time (that is 2 min for class C, 2.5 min For class B and min for class A). The number that results from this calculation is normally less than a whole number but should be rounded up if it greater than or equal than 0.3. The minimum number of exits is determined by the maximum size of exits in the building and the number of units of the widths of exits. It is expressed by the equation; E= U/ 4 + 1 where: - E= number of exit U= number of units of exit width 4= size of the largest exit permitted 1= It is added in order to ensure that one unit is always there 5.2 Stair provisions It is a form of vertical escape route mechanism. Escape stairways should be fire resistant and prevent smoke from entering them. They should have windows that can be opened easily to allow fresh air. In addition, they should be free from any obstacles such as storage cupboards. Width of escape staircases largely depends on the kind of evacuation that might be employed at the breakout of fire but is preferably 1150mm (Sheridan et al 2003). 6.0 Conclusion The B1 section of the building regulation has explicitly stated all the requirements needed for construction of a building that will ensure safety of its occupants in the event of a fire. Detection and alarm systems should be a crucial consideration when designing a building. The ways in which these systems are installed differ significantly depending on the nature and usage of the building as stated by the regulations. The regulation also provides various recommendations for escape or evacuation from a building on fire. Travel distance which is the nearest distance to an exit should be as short as possible. Exit width of escape routes should be sufficiently enough to permit any activity during evacuation. Buildings should have adequate number of escape stairways which should be constructed in accordance with the regulations. References Billington, M., Bright, K. and Waters, J. 2007. The builing regulations: Explained and illustrated. Oxford: Blackwell Publications. Communities and local Government. 2007. Fire safety. Retrieved on 22nd February 2012 from http://www.planningportal.gov.uk/uploads/br/BR_App_Doc_B_v2.pdf. Office of the Deputy Prime Minister. 2000. Fire safety. Retrieved on 22nd February 2012 from http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADB_2000.pdf. Sheridan, L., Visscher, H. and Meijer. 2003. Building regulations in Europe. Part 2, A comparison of the technical requirements in the eigth European Countries. Delft: DUP Science. Read More