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Section 6 - Design by Fire EngineeringClause G6.1 Application of Fire Engineering at Different StagesThe application of fire engineering at different stages of a project (fire engineering process)is described below for new buildings. For existing buildings, the role and involvement willdiffer, depending on the alterations, additions or changes in Use Classification that areproposed:(a) Building Planning / Feasibility(i)The role of fire engineering is to identify areas of non-compliance with theDeemed-to-Comply provisions and provide generalised design adviceregarding occupant type, numbers, FRR, fire safety provisions, site access,neighbouring buildings etc. in broad terms.(b) Schematic Design(i)As the design detail advances, the major fire safety provisions can beconfirmed.(c) Detailed Design(i)As the design proceeds to a detailed design stage, all fire safety provisionsand Alternative Solutions should be addressed in detail. The FSAR should becompleted for submission and acceptance.(d) Construction(i)During construction stage, fire safety provisions may change or require reassessment. A revised FSAR should be submitted as appropriate.(e) Commissioning(i)Towards the end of the construction, all fire safety provisions will requireinspection and commissioning. The authorized person should be involved andconfirm that all fire safety provisions are installed as per the approved plans,FSAR and related documents (reports, drawings and specifications).(f) Management in Use(i)The authorized person should assist in documenting all Bounding Conditionsthat will form part of a fire safety management plan. He should also assist todevelop maintenance and management procedures for the building owners.Clause G6.2 Fire Engineering ProcessFeasibility and Schematic DesignDuring the early stages of a project, whether it be a new building or addition and alterationworks to an existing building, fire engineering may be used in two different ways, namely inthe design and assessment of fire safety sub-systems or in the evaluation of a specific firesafety provision.In the early stages of a project, where the building design is evolving, the fire engineeringprocess may contribute to the development of the design and the evaluation of the variousdesign options. In the later stages, when the design has become essentially fixed, a fireengineering evaluation should be carried out to demonstrate that the Alternative Solution206
complies with the relevant fire safety objectives and Performance Requirements in thisCode, utilising the approach and methodology of the fire safety sub-systems.From this latter process, an FSAR is generated which forms the basis of the documentaryevidence required in support of an Alternative Solution.Clause G6.3 Pre-submission EnquiryIf fire engineering is adopted, the authorized person should consider the implications of firesafety on the building design and consult the Building Authority at the early stage so that thefire safety objectives can be agreed at the outset. In this connection, the Building Authoritymay be approached prior to submission of general building plans for agreement in principleto any fire engineering design being considered.The authorized person should take on a pivotal role in the consultative procedures when thefire strategy and fire engineering design is being developed.The authorized person should then submit the FSAR together with the general buildingplans to the Building Authority for approval.Clause G6.4 Assessment ApproachesThe principles of design of Alternative Solutions should be based on assessing the firesafety sub-systems and their interaction with each other.The basis of many life safety assessments for a fire engineering approach is the utilisationof the “time-line” method where the “required time” for egress is compared withthe ”available time” for egress. This approach is the “RSET versus ASET” approach, whereRSET is the Required Safe Egress Time and ASET is the Available Safe Egress Time. Thisinvolves the interaction of the sub-systems 1 to 5. This can lead to the assessment andjustification. For example, travel distances that exceed the Deemed-to-Comply provisions inthis Code.An Alternative Solution should follow one of the following three assessment methods for fireengineering:(a) Assessment Type 1: Qualitative analysis or quantitative with calculations, generallybased on a simple assessment involving a single sub-system. This may be anequivalence assessment.(b) Assessment Type 2: This assessment involves a quantitative analysis of more thanone sub-system, but does not involve detailed analysis of all sub-systems. Theassessment can be a deterministic, absolute or comparative analysis, based on theassessment of multiple fire scenarios. An equivalence assessment may form part ofthis process.(c) Assessment Type 3: This assessment involves all six sub-systems and theevaluation should be based on probabilistic methods. As there is currently nomethod or means to establish an absolute acceptance criterion, only comparativeanalysis will be accepted. This assessment can only be used for special or complexbuildings.Assessment Type 2 is the most common type of analysis. A time line assessment isillustrated in Diagram G1, showing the basis of Assessment Type 2, which consist of thefollowing aspects:207
(i) evacuation assessment, made up of detection time, pre-movement time,physical travel time, and time to exit from a fire compartment;(ii) fire development calculations showing rate of heat release for a fire within thefire compartment for a range of scenarios;(iii) smoke development calculations for the fire compartment; and(iv) safety factor or safety margin as part of the comparison of the two timelines.Time line assessments provide a very clear and transparent process for assessing a firesafety design. The time line assessment has three parts – tenability calculations, means ofescape calculations and a safety margin (or factor).Diagram G1: Graphical Representation of a Timeline AssessmentClause G6.5 Design FiresA design fire is an engineering description of the development of a fire for use in a designfire scenario. Design fire curves are described in terms of heat release rate (HRR) versustime. The formulation of a design fire is crucial to any fire safety design as the design fireacts as the “test load” to the proposed fire safety strategy.A fire is either fuel controlled or ventilation controlled. Fuel controlled fires are typicallyrepresented by short period fires, with steep HRR curves. If the ventilation is limited withinthe fire compartment, then the HRR will be limited, due to the limited oxygen available forcombustion. Ventilation controlled fires are typically represented by longer duration fireswith HRR curves that have a less steep curve.In developing a design fire, the effects of the fire growth characteristics, the mass of fuel,the layout of the fuel and the effects of the fire compartment on the combustion processesshould be taken into account as appropriate to justify the design fire.A typical schematic HRR curve for a fire compartment is shown in Diagram G2 below. Thiscurve illustrates the main aspects of HRR within a fire compartment. Each phase is furtherdescribed.208
FlashoverGrowthFully DevelopedDecayHeat Release RateIncipientTimeDiagram G2: Typical Phases of a Fire CurveIncipient PhaseThe incipient phase of a fire can last a few milliseconds to days depending on the initialfuels involved, ambient conditions, ignition source, etc. In most cases, the incipient phase isignored and the growth phase is started from time zero.Growth PhaseThe growth phase is considered to begin when the radiation feedback from the flamegoverns the mass loss rate. Assuming the fire compartment is vented, the burning rate isprimarily influenced by the fuel properties and orientation. During the growth phase the firespreads across the fuel surfaces, increasing the burning area and corresponding HRR. Themass loss rate is assumed to be independent of the fire enclosure and governed more bythe flame-spread rate.The growth phase is the most important aspect of the design fire. This is typically modelled2with a t rate of growth.CommentaryThe ability to predict flame spread through empirical models has encouraging results but islimited to comparatively simple geometries such as room corners. Research on the growthrate for complex objects like upholstered furniture and complex storage arrays is ongoing.Therefore, fire safety consultants are forced to using experimental data or correlations toestimate the fire growth rate.FlashoverAlthough there is no universally accepted definition for flashover, it can be described as atransition from a developing fire to full room involvement. This transition typically occursover a short time span measured in seconds. The increase in radiation from the upper layernot only ignites all of the combustibles in the room but also enhances the mass loss rate ofall the burning objects.209
Typical definitions of flashover including:o(a) Gas temperatures at near ceiling level in the order of 600 C;2(b) Radiation heat flux at floor level exceeding 20 kW/m ; and(c) Flames emerging from enclosure openings.These definitions are practical criteria for physical observation only. From a modelling pointof view, flashover is modelled as a linear transition from a growing fire to a fully developedfire over a very short period of time.Fully Developed / Post-FlashoverIn the fully developed or post-flashover phase of the fire, all of the combustible objects in thefire compartment are burning including the floor (if combustible). The mass loss rate iscontrolled either by fuel surface area or the available air supply. In most cases, the fire iscontrolled by the available oxygen, i.e. ventilation controlled.CommentarySome fire models calculate the ventilation rate into and out of a fire compartment and havethe capability to adjust the HRR within the fire compartment accordingly. Any excess fuelthat cannot burn within the fire compartment due to a lack of oxygen is available to burn inother locations where there is sufficient oxygen (i.e. outside the openings).Decay PhaseOnce a fire has consumed most of the available fuel the HRR will diminish.Determining Appropriate Design FiresA fire engineering assessment should be based on the establishment of appropriate designfires, which should be based on:(a) Use Classification of the fire compartment;(b) fire load energy density information;(c) typical configuration of fuels;(d) ventilation conditions; and(e) fire suppression systems or passive fire safety provisions.A range of design fires should be established for an assessment or a conservative designfire may be chosen.Initiation of a fire, or the ignitability of an object is normally not analysed but assumed tooccur and the growth of fire is modeled. The initial growth of the fire, once started, can beparticularly important for aspect of fire spread and tenability. Estimating fire spread betweenobjects is often calculated to assess how quickly a fire within a fire compartment mayspread.210
CommentaryDifferent design fire scenarios should be developed with an aim to approximate credible firescenarios (including small arson with small fire size, as appropriate) to test the robustnessof the Alternative Solution.The number, type and location of design fires are dependent on the building type and theAlternative Solutions being assessed. A risk-based approach to developing design fires canalso be utilised, where the design fires to be chosen are not clear or there are a multiplenumber of design fires to be assessed.Quantification of design fires will be dependent on the Use Classification, the ventilation, theagreed types of fuel present and will therefore vary between projects and be applied on acase-by-case basis for each project.A significant amount of detailed information relating to design fires is available through peerreviewed journals and key references. The process of choosing and quantifying theappropriate design fires is to be based on the realistic expectations for ignition hazards, firegrowth, combustibles reasonably expected and fire duration, based on the ventilationconditions.By considering possible scenarios as part of the FSAR, the expectations of analysis for thefire engineering assessment can be readily determined. The fire safety sub-systemsapproach to analysis assists in developing the appropriate sensitivity of input parametersand redundancy of fire safety provisions installed.2A common method of describing growing fires is the “T-squared” (or t ) concept. T-squaredfires are generic fire growth rates based on fuel characteristics and are the most commonand practical curves for estimating the growth of a fire. These curves are defined in NFPA1292B and Enclosure Fire Dynamics . The “T-squared” curves as they are often referred toare design tools to represent fire growth rate of general combustible items. There are fourcurves used, slow, medium, fast and ultra-fast.1NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and Large Areas, National Fire ProtectionAssociation, Quincy, MA, 2009.2Karlsson, B., and Quintiere, J. G., Enclosure Fire Dynamics, CRC Press, Boca Raton, FL, 2000.211
Examples on Design FiresTypical examples on design fires are provided in Table G1 for reference. These examplesare deduced based on the parameters given in the Table. The suitability on adopting thedesign fire provided in Table G1 should be considered diligently and be verified on case-bycase basis.Table G1 – Examples on Design Fire SizesUse ClassificationExamples on Design Fire Size1. ResidentialFor considering a pre-flashover fire, the growth rate of designfire for residential is medium. See Note (1).For considering a post-flashover fire, the most commonly useddesign fire depends on Ventilation Controlled Fire. Note (2)illustrates an example on the calculation methodology.2. Hotel and similar TransientAccommodationSprinkler controlled fire for a hotel room with a headroom of3.0m and standard response type of sprinkler is expected to beabout 1.7MW.3. Institutional3a. Health/childcare facilitiesSprinkler controlled fire for a hospital with a headroom of 3.0mand standard response type of sprinkler is expected to be about1.7MW.3b. Detention andcorrectionalcentresSprinkler controlled fire with a headroom of 2.5m and standardresponse type of sprinkler is expected to be about 1.5MW.4a. BusinessfacilitiesSprinkler controlled fire for an office with a headroom of 2.5mand standard response type of sprinkler is expected to be about1.5MW.4b. MercantilefacilitiesSprinkler controlled fire with a headroom of 2.5m and standardresponse type of sprinkler is expected to be about 1.5MW.4. CommercialIf no sprinkler is provided, the fire size is expected to be basedon fuel load density obtained by measured survey loads, q, 2which is given in MJ · m . By assuming a conservative burnout time of 20 minutes (i.e. 1200 s), the unit heat release isestimated to be:QU q / 1200 2where QU (kW · m ) is the unit heat release rate and q (kJ · 2m ) is the measured survey load. See Note (3) for an example.5. Assembly5a. Places ofPublicEntertainmentSprinkler controlled fire with a headroom of 2.5m and standardresponse type of sprinkler is expected to be about 1.5MW.5b. Educationalestablishments212
Use ClassificationExamples on Design Fire Size5c. TransportfacilitiesSee Note (4) for vehicle fires.Range from 5 MW to 22 MW for train fire. See Note (5).5d. OtherAssemblyPremisesSprinkler controlled fire with a headroom of 2.5m and standardresponse type of sprinkler is expected to be about 1.5MW.6. IndustrialSprinkler controlled fire for an industrial building or a warehousewith a headroom of 3.5m and standard response type ofsprinkler is expected to be about 2.0MW.7. CarparkCarparks should be protected by sprinklers as required by FSICode. Any fire in the carpark is expected to be controlledavoiding any fire spread from one vehicle to another. See Note(6) for details.8. Plant rooms & the likeSprinkler controlled fire for a plant room and the like with aheadroom of 3m and standard response type of sprinkler isexpected to be about 1.7MW.Notes:(1) Reference can be made to CIBSE Guide E Fire Safety Engineering, The CharteredInstitution of Building Services Engineers, London, 3rd Edition, 2010.(2) An example for a residential unit with the living room dimension of 6m (L) x 3m(W) x 3.2m(H), having two windows of 3m (W) x 2.5m(H) and 0.8m(W) x 1.2m(H) based on the3equations in CIBSE Guide E and CIBSE TM19 . The rate of burning is calculated as: R 0.02 Ao h1 2 AT Ao (W D) 12(Equation 1)Where,2Ao Sum of window areas, m² 3 x 2.5 0.8 x 1.2 8.46mAT Total area is the area of room surface (wall, floor, ceiling), m 6 x 3 x 2 (3 6) x 2 x 3.2 93.6mh22 Weighted average of window height, m (3 x 2.5 x 2.5 0.8 x 1.2 x 1.2 ) 8.46 2.3525 m3W Width of the wall containing window, m 3mD Depth of room behind the window, m 6mCIBSE Technical Memoranda TM19, Relationships for Smoke Control Calculations, Chartered Institution ofBuilding Services Engineers, London, 1995.213
For multiple openings with different heights, h can be calculated by:h Ahi iAw(Equation 2)where, i 1, 2, 3 .represents different windows.D /W W2 Aw1W1 Aw(Equation 3)where,W1 Width of wall 1 (containing the greatest window area), m 3mW2 Width of wall 2 (depth of room behind the greatest window area), m 6mAw1 Window area on wall 1, m² 3 x 2.5 7.5 mAw Sum of window areas on all wall, m² 8.46mTherefore, D / W R 0.02 Ao h12 AT22W2 Aw1 6 7.5 1.77W1 Aw3 8.46 Ao (W D) 121 0.02 8.46 2.35251 / 2 (93.6 8.46)()1.77 1/ 2 0.5kg / sThe equivalent heat release rate is given by Q H c x R, where Hc is the heat of combustion(kJ/kg) and R (kg/s) is the mass rate of burning. When assuming the burning material is33wood (Hc 13.0 x 10 kJ/kg), the calculated heat release rate is equal to 13.0 x 10 x 0.5 6.5 MW.(3) Design Fire based on Measured Survey LoadQU q / 1200 2 2where QU (kW · m ) is the unit heat release rate and q (kJ · m ) is the measured surveyload.-2A commonly used value of unit heat release rate for retail shop is 550 kWm as shown inTable 6.3 of CIBSE Guide E. Therefore, when considering an example of a retail shop with222the floor area of 50 m , the total heat release rate is about 550 kW/m x 50 m 27.5 MW.(4) For Use Classifications 5c and 7, the examples of fire size for different types of vehicles forroad tunnel design can make reference to NFPA 502, Standard for Road Tunnels, Bridges,and Other Limited Access Highways, National Fire Protection Association, Quincy, MA,2011 and Ingason, H., “Design Fires in Tunnels”, Second International Symposium,Lausanne, 2006. The following should also be considered:(i) The designer should consider the rate of fire development (peak HRR may bereached within 10 minutes), the number of vehicles that could be involved in the fire,and the potential for the fire to spread from one vehicle to another.(ii) Temperatures directly above the fire can be expected to be as high as 1000 C to1400 C (1832 F to 2552 F).(iii) The HRR may be greater than in the table if more than one vehicle is involved.214
(iv) A design fire curve should be developed in order to satisfy each specific engineeringobjective in the design process (e.g., fire and life safety, structural protection, etc.).(5) The examples on design fire sizes are adopted in some projects of Mass Transit RailwayCorporation. The design fire sizes depend on the type and model of the trains.(6) Though sprinklers are provided for carparks, there is experiment comparing the fire sizes fortwo different situations: (1) a free burning vehicle with no sprinkler and (2) a burning vehiclewith sprinklers. The fire sizes of the two situations are very similar. This is because thevehicle has a canopy at the top which can shield off the sprinkler water and cannoteffectively suppress or control the fire inside the car.Commentary4Examples of the expected HRR for various items may refer to NFPA 92B ,, as are thedesign curves. They represent a general worst credible fire scenario that is easily compared,as a basic design tool. When fuel items are burnt and the data recorded, it can be compared2with the t fire growth curves.The amount of fire load has been traditionally perceived to be related directly to fire growthrate, i.e. a higher fire load density will lead to a faster fire growth. Scientifically, how fast afire grows depends on the fuel properties (e.g. liquid fuels burn much faster than solid fuels),the exposed surface area, and the amount of external heat energy and oxygen available tothe fuel.The quantity of fire load has also been used to represent the degree of fire hazard inbuildings. Whilst it is correct that an enclosure having more fuel will lead to a longer fireduration (under same ventilation conditions), sole reliance on fire load density tocharacterize fire hazard has not addressed other parameters that equally contribute to thefire hazard, including potential fire growth rate, flame spread properties of furnishings, easeof ignition of the dead and live fire load in the enclosure, the potential ventilation availablethrough door and window openings, and the likely types of ignition source.The following references are suggested:4 CIBSE Guide E Fire Safety Engineering, The Chartered Institution of BuildingServices Engineers, London, 3rd Edition, 2010. PD 7974-1, The Application of Fire Safety Engineering Principles to the Design ofBuildings – Part 1: Initiation and Development of Fire within the Enclosure of Origin(Sub-System 1), British Standards Institution, London, 2003. ISO/TR 13387-2, Fire Safety Engineering – Part 2: Design Fire Scenarios andDesign Fires, British Standards Institution, London, 1999. NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and LargeAreas, National Fire Protection Association, Quincy, MA, 2009. Society of Fire Protection Engineers, SFPE Engineering Guide to PerformanceBased Fire Protection Analysis and Design of Buildings, National Fire ProtectionAssociation, Quincy, MA, 2000. NFPA 502, Standard for Road Tunnels, Bridges and Other Limited AccessHighways, National Fire Protection Association, Quincy, MA, 2011. Ingason, H., “Design Fires in Tunnels”, Second International Symposium, Lausanne,2006.NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and Large Areas, National Fire ProtectionAssociation, Quincy, MA, 2009.215
Clause G6.6 Smoke ControlIn general, smoke control (smoke hazard management) systems are designed to:(a) reduce the impact of smoke and heat on occupants evacuating from a firecompartment where a fire is located; and(b) limit the spread of smoke between fire compartments.The impact of smoke from a fire can be controlled through both active and passive firesafety provisions. Active fire safety provisions are activated by smoke detection or sprinklerprotection and include fans to exhaust smoke, operable vents or other systems such assmoke curtains and shutters. These systems will control and vent both heat and smoke toreduce the spread of smoke and also permit evacuation by occupants.Smoke can also be controlled by passive fire safety provisions, which includescompartmentation that limits fire spread within a building.CommentaryThe design for the control of smoke within a fire compartment or atrium is complex andrequires detailed understanding of fire growth, fluid dynamics and building safety systems.The design for smoke hazard management systems must include careful consideration ofmake up air. The impact of wind would only be considered for smoke control with the use ofnatural ventilation.Smoke hazard management for occupant safety will have different design and acceptancecriteria than smoke clearance systems, which are designed to vent smoke to assistfirefighting activities.Guidance for the design of smoke hazard management systems should be sourced fromguides such as those listed below: PD 7974-2, The Application of Fire Safety Engineering Principles to the Design ofBuildings – Part 2: Spread of Smoke and Toxic Gases within and beyond theEnclosure of Origin (Sub-System2), British Standards Institution, London, 2002. NFPA 92B, Guide for Smoke Management Systems in Malls, Atria, and LargeAreas, National Fire Protection Association, Quincy, MA, 2009. CIBSE Guide E Fire Safety Engineering, Chartered Institution of Building ServicesrdEngineers, London, 3 Edition, 2010. ISO/TR 13387-5, Fire Safety Engineering – Part 5: Movement of Fire Effluents,British Standards Institution, London, 1999. Klote, J.H., and Milke, J.A., Principles of Smoke Management, American Society ofHeating, Refrigerating and Air-Conditioning Engineers, Inc. Atlanta, GA, 2002. Morgan, H.P. et al., Design methodologies for smoke and heat exhaust ventilation,BRE 368, Construction Research Communication Ltd, London, 1999.216
Clause G6.7 Occupant MovementOccupants within a building need various cues before they decide to evacuate. These cuesinclude visually seeing smoke or warnings from other persons. Another cue is an effectivealert and warning system. This includes tones and recorded or live messaging systems, withclear instructions.The time taken from when a fire is detected, either through smoke detection or other form ofdetection to when occupants start to evacuate, is the pre-movement time. The premovement time is a variable as persons will receive different cues and persons in differentlocations will react in a diverse manner. The pre-movement time varies as persons havedifferent commitments to the activities they are involved at the time of the fire, whether thatbe working, shopping, sleeping or watching a movie. Hence, pre-movement time should bea distribution.Pre-movement time also varies between Use Classifications. Persons who are asleeptypically take much longer time to react and prepare themselves to evacuate. Persons whoare working are relatively alert and are more familiar with the exits and surroundings. TableG2 summarizes various well-referenced pre-movement times. The same set of guidelinesshould be applied consistently throughout the whole fire safety assessment.217
Table G2 – Summary of Pre-movement TimesAll values are in minutesNote a:Pre-movement time of the first few occupantsNote b:Pre-movement time of the last few occupantsNote c:For a large complex building, add 0.5Note d:For a simple multi-storey building, add 0.5Note e:For a large complex building, add 1.0Note f:These times depend upon the presence of staffReferences used:[1] PD 7974-6, The Application of Fire Safety Engineering Principles to the Design of Buildings – Part 6: HumanFactors: Life Safety Strategies – Occupant Evacuation Behaviour and Conditions (Sub-System 6), BritishStandards Institution, London, 2004.[2] Proulx, G., “Movement of People,” in SFPE Handbook of Fire Protection Engineering, 3rd ed., Section 3,Chapter 13, P.J. DiNenno et al. (Eds.), National Fire Protection Association, Quincy, MA, 2002.[3] Beever, P, et al., “A New Framework for Performance Based Fire Engineering Design in New Zealand,” 8thInternational Conference on Performance-Based Codes and Safety Design Methods, Sweden, 2010.[4] CIBSE Guide E Fire Safety Engineering, Chartered Institution of Building Services Engineers, London, 3 rdEdition, 2010.218
Clause G6.8 Tenability CriteriaFor the purposes of assessing quantitative modelling results, tenability criteria are required,which are assumed to provide an indication of the level of life safety for evacuatingoccupants with respect to the heat and smoke conditions within the building. Authorizedpersons should propose for the Building Authority’s acceptance the most appropriatetenability criteria for their Alternative Solution.Factors that may affect the tenability criteria include Use Classification and variation in sizeof fire compartments or buildings.Tenability is normally determined by assessing one or all of the following:(a) smoke layer height;(b) radiated heat transfer;(c) convected heat transfer;(d) toxicity;(e) visibility;(f) smoke temperature.Smoke Layer Height2m should be adopted as the acceptable smoke layer height unless otherwise justified bythe authorized person.CommentaryWhilst accepted values for smoke layer height have varied in the past for Hong Kong,Paragraph 1.1.2(a) under Part IV of Fire Services Department Circular Letter No. 4/96states that apart assisting firefighters, a smoke extraction system has advantages:“assisting in the provision of clear egress for escaping persons. Generally a smoke freezone of 2m in height is to be aimed for in the design. “Smoke free” does not imply completeelimination of smoke, but that visibility is not greatly impaired”.Values adopted overseas are provided below for information:5 PD 7974-6, The Application of Fire Safety Engineering Principles to the Design ofBuildings – Part 6: Human Factors: Life Safety Strategies – Occupant EvacuationBehaviour and Conditions (Sub-System 6), British Standards Institution, London,2004. In Australia, the National Construction Code Series (previously referred to as theBuilding Code of Australia) requirements for smoke exhaust capacity in Spec E2.2b,are based on keeping smoke 2m above the floor. In New Zealand, as described in the Fire Engineering Design Guide , a layer heightof 2m is used.5Fire Engineering Design Guide, Centre for Advanced Engineering at the University of Canterbury, Christchurch,New Zealand, 2008.219
Radiated Heat TransferRadiated heat transfer occurs when the smoke layer is above occupants’ heads, and is afunction of the smoke layer depth, smoke layer emissivity, and distance from the smokelayer to occupants. Radiated heat transfer can also impact on occupants who are in the hot2osmoke layer. A value of 2.5 kW/m (in the order of 200
A design fire is an engineering description of the development of a fire for use in a design fire scenario. Design fire curves are described in terms of heat release rate (HRR) versus time. The formulation of a design fire is crucial to any fire safety design as the design fire acts as the "test load" to the proposed fire safety strategy.
