Design of Fire Alarm and Detection Systems - Term Paper Example

Fire safety Engineering Name Subject Instructor Institution Date Abstract Functional requirement is an important aspect in design and constructions of building to ensure that, the building is safe from fire accidents. This has to be attributed to the functional requirement B1 of the Building regulations and review the standard of UK prescriptive and performance based design guidance (ADB, BS999 BS7974). Building regulations apply to extension, alteration, and construction of new buildings. The materials, standards, design and technical specification referred to in this report are those which are suitable for regulation purposes. B1 Building regulations objective is to make sure that there is a satisfactory standard that can be used as a means of escape in case there is fire in a building. These regulations states that a building shall be designed and constructed with adequate means of escape in the event of fire to safety area outside the building. The paper addresses fire alarm and detection systems, building occupancy, purpose groups, and horizontal and vertical escape route design principles which include; travel distances, exit widths and stair provisions. Table of Contents Table of Contents 3 1 Introduction 4 1.1Fire alarm and detection systems 7 2 Design of Fire alarm and detection systems 9 2.1 Behaviour of people 11 2.2 Recognition time 11 2.3 Response time 12 3 Building occupancy and Purpose groups 12 4 Design for Horizontal the escape route 14 4.1Alternative escape routes 15 4.2 Planning for horizontal evacuation 16 5 Designs for Vertical Escape 16 5.1 Single Escape Stairways 17 5.1.1Width 17 6 Conclusion 17 1 Introduction Fire in a building is a very complex phenomenon and on-going developments are underway to improve safety and understanding of different behaviours and consequences in the events of fire. The British engineering standards provides guidance and directions on means of escape and warning, fire spread in and outside the buildings, access to the building and a suitable facility that can be used in fire fighting as noted Albrecht and Hosser (2011). Designers must be aware of the changes in regulations, standard prescriptive, and performance based design guidance. For instance, as noted in the Fire Safety EngineeringCIBSE Guide (2010), the BS 9990 stipulates code of practice used in non-automatic fire-fighting equipment and systems in a building. BS 7974 standard is applicable in fire safety engineering principles in the nature in which building are designed. Many analytical models based on mathematical relationship have been developed to cater for different conditions in the event of fire. There are also different computer based models used in predicting different behaviour in the event of fire and the consequences involved. Great care must be taken when models are being developed to cater for results validity (Avillo, 2002). Proper understanding of assumptions, parameters and limitations in different models, accuracy, applications and correct interpretation of output is a requirement. B1 requirement can be met by ensuring that escape routes are enough in a building which are of good size, suitably located to make it possible for someone to escape to safely in case fire is detected as noted by Law and Gillie (2011). Routes should be sufficiently protected from fire effects. Materials used in constructing these routes should be free from effects of fire. There should be sufficient lighting, smoke should be controlled problem in the routes of escape and the alarm systems must warn the building occupant presence of fire in timely manner to enable them to escape safely. Provision of B1 of the Building regulations are concerned with different measures essential in ensuring that, there is reasonable facilities that can be used as means of escape. The structural precautions are a necessity in safeguarding the escape routes. This precaution are created in assumption that Building occupancy comprises a proportion of people with physical challenges or disabilities thus, in designing the building, escape and rescue reliance should not only be trusted of fire brigades (Sabaei, 2006). The report has hence been prepared based on the argument that all occupants in a building should escape safely from a fire stricken building without external assistance. Attention is drawn due to the fact that, some other legislation may require buildings to comply with regulations pertaining to means of escape in the event of fire. This legislation includes fire service acts, health and workers welfare acts. It is a requirement that design of means of escape be based on the probable behaviour of fire. Fire cannot be predicted and may break out when not expected in any part of the building spreading to other parts and thus, the overall building design need to be analyzed carefully to determine the extent of danger from fire (Hume and Mick, 2002). Fire create hazard mainly in the part of the building that it starts. Subsequently, it spreads to other parts of the building and mostly along building’s circulation routes. Primary danger in fire outbreaks in the early stages is mostly not the frame but noxious gases and frames produced by fire. In the event of fire most of the casualties are affected by smoke. Smoke obscure escape and exit routes. Thus, there should be measure to limit spread of smoke and fumes. Good criteria to be used as a means of escape should ensure that, there is alternative escape means where possible. If direct escape to safety is not possible, it is required that, the two parts of escape means be used. These include; Unprotected route of escape limited in extent. This route should lead to safe escape route. Protected route of escape which should lead to an area safe from fire. Place of safety is ultimately an open area, with free circulating air and clear of fire effects. In large and complex buildings, safety is ensured by incorporating planning and protection measures to guidance presented in this document. The following should not be used as a means of escape; Lifts-except lift designed specifically for evacuation the passenger escalators and conveyors manipulative appliances and apparatus throw-out ladders and portable ladders 1.1Fire alarm and detection systems Occurrence of fire may cause untenable situation making the escape routes even unusable. These conditions occur sometimes after outbreak of a fire and the faster the outbreak is detected, the better the situation as more evacuation time will be available (Avillo, 2002). Buildings must have a fire alarm and detection system to inform and warn the building occupancies of the fire outbreak. Fire alarm and detection systems are mostly essential in buildings where the size, layout and the nature of occupancy may be large enough. This makes it difficult for the outbreak of fire to provide adequate warning to enable the occupant to escape safely. Fire alarm and detection systems provision must comply with recommendation relevant in their design and installation. Fire alarm and detection systems guidelines for designing, planning, commissioning, installation, use and maintenance code of practice for system design, servicing and installation is provided. System provided should be capable of protecting the building and its occupancies by informing detection and occurrence of fire. In institutional building, there is a requirement of high level of protection and thus a level 1 Fire alarm and detection systems should be provided (Chitty and Jeremy, 2003). Design of such system requires much consideration on the category of the occupants, means of alerting fire outbreak and evacuation procedures. In a mixed-user building a Fire alarm and detection systems should be appropriate to Building occupancy, purpose groups, building size and layout. In Buildings with flats, individual dwellings should have fire alarm and detection system that complies with provision set (Tubbs and Brian, 2007). In a building containing flats, where the compartment floors and walls are constructed with combustible materials, type L3X fire alarm and detection system should be provided to protect common escape route. Buildings made from non-combustible material, manual fire alarm should be provided in building escape route. Fire alarm and detection systems designed should incorporate different measures that can be used in reducing false alarm risk or misuse and should provide a way of initiating building evacuation process. Consideration must be taken to ensure that large buildings fire systems warn the occupancy that the building has been affected by fire. Fire alarm and detection systems can increase safety level in dwelling houses. System in these houses should be provided according to regulation and guidance in Fire alarm and detection systems for buildings guidelines. The code of practice used for installation and design of Fire alarm and detection systems in houses provides regulation outlined in requirement B1 of the Building Regulations. Standards provided refers to different grades that can provide different levels of protection. This has to entail the calculation in the exposure of fire in relation with the time that the fire exposure has taken. This has to be analyzed using the ire curves which give an indication in the time of exposure of various materials. Various architectural designs have to be in cooperated in the building process so as to ensure that the building is safe from fire accident (Tubbs and Brian, 2007). The smoke may be controlled by use of the stand pipes. It is vital to control the flow of smoke since it is rises easily in building due to the fact that it is warm and would tend to rise higher in buildings. They also occupy the building at a faster rate due to the stack action making them to rise very fast in the building. In order to curb such scenarios, the smoke shafts may be erected so as to reduce the smoke volume. This has to be done by erecting the smoke shaft that have to occupy the whole building and have to have the dampers at the end of the building so as to their openings are sealed. As noted by Biondini and Dan (2008), amount of smoke may also be reduced by using non combustible materials in the building and by use of the automatic sprinklers. The relation between the various compartments of the building and the atmospheric condition may be determined by use of natural calculation of fire. This would give a clear indication in the behaviour of fires. In order to ascertain the duration in which a given beam may withstand the fire without collapsing, the results obtained from the graph calculations are vital in making the required decision. 2 Design of Fire alarm and detection systems Essentially, fire alarm and detection systems should be suitable to the number of storeys and the size of the building as noted by Albrecht and Hosser (2011). Fire alarm and detection systems should have control and indicating equipment maintained and installed according to regulation provided in requirement B1 of the Building Regulations. The system should have fire detectors, control, fire alarm sounders, and indicating equipments. Fire alarm should be interconnected with smoke and heat alarms in order to sound the alarm if any of the unit detects fire. Heat detectors must be provided in areas where fire is used in day today activities for example in the kitchen. Buildings having three storeys and above or where the risk of fire is so warrant, LD1 system should be provided as appropriate. This would ensure high level of security. The exit has to be connected to the vestibular in order to ensure that the exit is easily accessed without necessary using the interconnected space. The draft stops have be put in place so that they act as the smoke reservoirs to the adjacent surrounding Albrecht and Hosser (2011, p. 1062). This requires that the whole storied building has to be draft which occupies the whole building. The building materials have to be build with materials which are non combustible to prevent further spread of fire in case of a fire outbreak. This may be achieved by using materials such as heavy timber. The sprinklers have to be installed in the building with in cooperation of the vestibular in each floor. This has to be in cooperated with the exit openings which would be in cooperated in each vestibular which would protect the elevators. The building has to be in cooperated with mechanism that would aid to remove the smoke so as to enable the fire fighters to combat with the fire. In order to detect the amount of fire through the fuel and fire characteristics the following equation may be used; = Where =energy that is released per unit surface area of given fuel =The latent heat exhibited of vaporization =The heat of influx that represents the incident heat acting on a unit surface area. = Combustion heat exhibited This would aid in giving the combustion of heat of various substances. 2.1 Behaviour of people Designers should put in mind people’s behaviour when designing fire alarm. Delay must be avoided between when an alarm is sounded and the time people start evacuating the building. Some of the principles in modelling people’s behaviour include. Deaths in the event of fire attributed to panic are mainly caused be delays in receiving information about an outbreak of fire. Building occupancy should not only rely on fire alarms to prompt them to move to safety. People response to alarm is very significant than time taken to reach the exit. 2.2 Recognition time The period between an alarm sounding and the time when people start responding is the recognition time (Sabaei, 2006). Recognition time length is extremely variable and depends upon the nature of building occupants, type of building, fire management safety procedure and familiarity with fire alarm and detection system. 2.3 Response time The period of time between fire recognition and the time that they begin to respond is called response time. This time should be minimized as much as possible depending on circumstances of fire. Normal activities should cease and occupants must engage in different activities in response to potential emergency. Activities that should be undertaken during response time should include: Investigation to know the source, the reality and the significance of the fire alarm; All machines should be stopped; Money should be secured safely; The family members must be secured Important belonging must be collected The first aid and fire fighting equipment must be secured. 3 Building occupancy and Purpose groups Building occupancy reflect the number of people in a particular building. Design of building should be in such a way that eases of evacuating the building in the event of fire as noted by Fire Safety EngineeringCIBSE Guide (2010). Occupancy mobility, familiarity with surroundings and ease of finding escape route has a significant effect on time required in evacuating a building. Characteristic of the following kind of occupancy must be considered when designing a building. Occupants familiar with the building Occupant who sleep in the building and familiar with the building Occupant who sleep in the building and not familiar with the building Occupants who require assistance, that is, those in hospital and in nursing homes Occupants who are in custody such as in prisons, In situations where there are different uses of a building, different users must be treated as purpose group in their own right. These situations include: Flat or maisonette half the total floor area. Storage area, which is more than half the building floor area. Ancillary use of buildings if the area of the building is more than a quarter the total floor area. The purpose group providing generic means necessary in categorizing building use in the context of fire outbreak likelihood can be seen in the table below. Table 1 categorization of building usage Title The purpose of the building or compartment Institutional Hospital, school or other establishment that can be used as a living accommodation. It can also be building used for people with disabilities, suffering from illness, old age or people with mental or physical incapacity. People who are underage are also covered here. Hotel, residential college, boarding house, hostel, hall of residence or any other residential building. office May be used for administration, handling money, clerical work, and communication. It may also includes television, radio audio or video recording. Shop and commercial Buildings used for retail trade and businesses that includes sale of food and drinks, retail by auction, over the counter wholesale, self selection, periodicals and hairdresser. It also includes premises where people attend to collect commercial goods. Assembly and recreation This includes place of assembly, recreation or entertainment that comprises broadcasting, bingo halls, and recording and film studios. Industrial This includes factories and premises used for the purpose of manufacturing, repairing, altering, washing, cleaning, process and generating of power. Storage and non-residential premises This is a place where goods and materials are stored and any other building not described above Car parks designed to accommodate cars and motorcycle. Room or storey- this is the maximum number of people that a building is designed to hold. The maximum load factor can be given as below The area excluded includes stairway enclosures, sanitary and lifts. 4 Design for Horizontal the escape route When designing any facility to be used as an escape route in the event of an outbreak of fire, care should be taken to ensure that people involved make a safe escape (Hume and Mick, 2002). Design of the Horizontal escape route and exits should depend on the following. The number of occupants in a building, Limitation derived from the extent of travel distance. The minimum escapes routes needed in one building. Number of occupants - figure used in showing the number of occupants is the design figure. If the number of people in a building is not well known, the number should be calculated based on the occupant capacity. Number of people in a building determine the escape and exit width provision. Travel distance – travel distance in any building should not be more than the appropriate value specified. Permitted travel distance depends on availability of escape in one direction or in many directions. Escape route is availability in many directions in situations where alternative escape routes are provided. Alternative escape routes are of less significance if they have likelihood of being disabled simultaneously. Each escape route must be created in such a way that it is independent of any other route. Designer must ensure that alternative escape route satisfy the following criteria. They should be created in such a way that they are 45o apart in direction, They should be in direction of less than 45o apart, separated by fire-resisting construction, From any point which has an initial direction of escape, they should be in direction of 45o apart plus 2.5o per metre travelled in particular direction. 4.1Alternative escape routes In a single escape route to avoid building occupants being trapped by smoke or fire, alternative escape route should be provided except in Purpose group areas and institutional not likely to have more than 50 people, Buildings not likely to have more than 50 occupants or 20 occupants for residential buildings, provided that limit in one direction escape are satisfied. 4.2 Planning for horizontal evacuation Adjoining compartments where horizontal evacuation takes place should have enough floors to accommodate all occupants who may seek refuge there. This can be calculated based on design occupancy of the building. Every compartment should have an escape route which is independent of the route that joins different compartments together. 5 Designs for Vertical Escape Protected and adequately-sized escape stairway need to be provided for an effective evacuation. Any part of the building external walls should be made of fire restricting construction which is 9 m vertically below, stairways flights and landings leading downwards (MacCollum and Richard, 2005). It should also be within 1.8m vertically above stairways landings and flights leading upwards. Stair extending vertically at distance more than 30m should be provided with a width of 1.4m unless provided with central handrail. Building which are large require access to be provided for fire services. Stairways are also used in fire-fighting process. Thus, number of stairways may be a major concern of the designer. Storied building should have escape route which are independent of other escape routes provided for other purposes. 5.1 Single Escape Stairways In situations where building is being served by one escape stairway, Every storey must have a single escape way which is more than 5m above the level of the ground. For basement floor which has more than 3m vertical distance below the ground level, every basement storey must be provided with one escape route. 5.1.1Width Every escape stairway must be designed to be wide enough in order to accommodate number of people using it during an emergency. This was depends on the evacuation strategy and the number of stairways in the building. Vertical escape should be used for All the basement stairs All the stairs that serve the building within open spatial plan All the stairs that serve residential and recreation buildings external protection to protected stairway Travel distance – this is the shortest route that can be taken by a person during evacuation When there is fixed obstruction a along the stairway. 6 Conclusion In conclusion, some buildings have diverse ancillary to one another, that is, one building may have different independent functions. In this situation, each use must be considered to be in its own purpose group under its own right. In complex buildings, complex mix of uses may be available. In such case designers of the building should consider the risk factor that one portion of the complex building may have to another and the measures that necessary in reducing risk factor. Building access for people who have disabilities is a requirement in buildings. Thus, when designing escape routes, designer should assume appropriate number of people with disabilities. In multiple use building effect of different users must be considered in order to ensure that means of building escape is not prejudiced in any way. If the security requirement in particular building have possibility of compromising availability of exits, measures should be taken to make sure that escape route and exits are availed to all occupants in case of an emergency. Functional requirement B1 of the Building Regulations provide provision for the classification of purpose group. Purpose groups must be decided at first before provisions are determined. Purpose group may apply to the whole building or to different compartments in the building. The relevant purpose groups are required to be taken from use of building compartment. References Albrecht, C., and Hosser, D., 2011. "A Response surface methodology for probabilistic life safety analysis using advanced fire engineering tools." Fire safety science 10(2), pp.1059-1072. Avillo, A., 2002. Fireground strategies: Fire Engineering. Tulsa, OK: PennWell. Biondini, F. and Dan, F., 2008. Life-cycle civil engineering: Proceedings of the first international symposium on life-cycle civil engineering. Boca Raton: CRC. British Columbia Fire Code, 2006. Victoria: Ministry. Chitty, R., and Jeremy, F., 2003. Fire safety engineering: A reference guide. London: BRE hop. Fire Safety EngineeringCIBSE Guide, 2010. London: Chartered Institute of Building Services Engineers. Hume, B. and Mick, E., 2002. The use of CFD computer models for fire safety design in buildings: Large warehouse case study. London: Office of the Deputy Prime Minister, Fire Research Division. Law, S, and Gillie, M., 2011. "Structural engineering and fire dynamics: Advances at the interface." fire safety science. 10(2), pp.1563-1576. Lo, S. and Min, L., 2008."A study on the effect of project coordinators' Knowledge on the use of performance-based fire safety engineering design in buildings." Journal of building appraisal, 4(1), pp.15-22. MacCollum, V., and Richard, H., 2005. Building design and construction hazards. Tucson, Az.: Lawyers & Judges Pub. Sabaei, S., 2006. Fire engineering: Prevention, protection and suppression of building fires. New York: Wiley. Technical Specification, 2006. Fire safety engineering: Selection of design fire scenarios and design fires. Geneva: International Organization for Standardization. Tubbs, S. and Brian, M., 2007. Egress Design Solutions: A guide to evacuation and crowd management planning. Hoboken, NJ: John Wiley & Sons. Read More

Provision of B1 of the Building regulations are concerned with different measures essential in ensuring that, there is reasonable facilities that can be used as means of escape. The structural precautions are a necessity in safeguarding the escape routes. This precaution are created in assumption that Building occupancy comprises a proportion of people with physical challenges or disabilities thus, in designing the building, escape and rescue reliance should not only be trusted of fire brigades (Sabaei, 2006).

The report has hence been prepared based on the argument that all occupants in a building should escape safely from a fire stricken building without external assistance. Attention is drawn due to the fact that, some other legislation may require buildings to comply with regulations pertaining to means of escape in the event of fire. This legislation includes fire service acts, health and workers welfare acts. It is a requirement that design of means of escape be based on the probable behaviour of fire.

Fire cannot be predicted and may break out when not expected in any part of the building spreading to other parts and thus, the overall building design need to be analyzed carefully to determine the extent of danger from fire (Hume and Mick, 2002). Fire create hazard mainly in the part of the building that it starts. Subsequently, it spreads to other parts of the building and mostly along building’s circulation routes. Primary danger in fire outbreaks in the early stages is mostly not the frame but noxious gases and frames produced by fire.

In the event of fire most of the casualties are affected by smoke. Smoke obscure escape and exit routes. Thus, there should be measure to limit spread of smoke and fumes. Good criteria to be used as a means of escape should ensure that, there is alternative escape means where possible. If direct escape to safety is not possible, it is required that, the two parts of escape means be used. These include; Unprotected route of escape limited in extent. This route should lead to safe escape route.

Protected route of escape which should lead to an area safe from fire. Place of safety is ultimately an open area, with free circulating air and clear of fire effects. In large and complex buildings, safety is ensured by incorporating planning and protection measures to guidance presented in this document. The following should not be used as a means of escape; Lifts-except lift designed specifically for evacuation the passenger escalators and conveyors manipulative appliances and apparatus throw-out ladders and portable ladders 1.

1Fire alarm and detection systems Occurrence of fire may cause untenable situation making the escape routes even unusable. These conditions occur sometimes after outbreak of a fire and the faster the outbreak is detected, the better the situation as more evacuation time will be available (Avillo, 2002). Buildings must have a fire alarm and detection system to inform and warn the building occupancies of the fire outbreak. Fire alarm and detection systems are mostly essential in buildings where the size, layout and the nature of occupancy may be large enough.

This makes it difficult for the outbreak of fire to provide adequate warning to enable the occupant to escape safely. Fire alarm and detection systems provision must comply with recommendation relevant in their design and installation. Fire alarm and detection systems guidelines for designing, planning, commissioning, installation, use and maintenance code of practice for system design, servicing and installation is provided. System provided should be capable of protecting the building and its occupancies by informing detection and occurrence of fire.

In institutional building, there is a requirement of high level of protection and thus a level 1 Fire alarm and detection systems should be provided (Chitty and Jeremy, 2003). Design of such system requires much consideration on the category of the occupants, means of alerting fire outbreak and evacuation procedures.

Read More