estimating water requirements for firefighting operations using fierasystem

Fire Technology, 37, 235–262, 2001© 2001 Kluwer Academic Publishers. Manufactured in The United States.

Estimating Water Requirementsfor Firefighting OperationsUsing FIERAsystem

David Torvi,1 George Hadjisophocleous,2 Matthew B. Guenther, andGordon Thomas, Fire Risk Management Program, Institute for

Research in Construction, National Research Council,Ottawa, ON K1A 0R6

Abstract. A new computer model for estimating water requirements for firefighting pur-poses has been developed by the Fire Risk Management Program of the National ResearchCouncil of Canada. This work was done in partnership with the Canadian Department ofNational Defence, as part of the development of a computer model to evaluate fire protectionsystems in light industrial buildings (FIERAsystem). The new model considers the geometryof the building, possible fire scenarios that may occur in the building, fire detector locationsand characteristics, the effect of automatic suppression systems on the fire, the locations ofadjacent buildings and the response and effectiveness of the fire department. The programcalculates the required flow rates of water at the time of fire department intervention forsuppression of the fire and for exposure protection for each side of the building. These flowrates can then be compared to the total capacity of the fire engines available to determineif existing resources are sufficient. The program has been designed to be interactive, so thatthe user can immediately see the effects of various parameters on the required water flowrate. Descriptions of case studies are also included to demonstrate the use of this model.

Key words: fire, firefighting, waterworks, planning, model

Introduction

A key part of fire department planning is estimating the necessary firefighting resourcesfor a community. Water, equipment and human resources must be selected based onthe possible fire scenarios that a department may respond to. Equipment and humanresources are, to a large extent, dependent on the required water supply for firefightingoperations.

Currently, several methods are commonly used in Canada and other countries to esti-mate these water requirements. Some of these methods rely on scientific principles, whileothers are based predominantly on empirical evidence. Some of the methods consider alarge number of factors, while others are based simply on the floor area of the buildingin question.

The Fire Risk Management Program of the National Research Council of Canada(NRC) has developed a computer model called FIERAsystem (Fire Evaluation and RiskAssessment) to evaluate fire protection systems in light industrial buildings, such as

236 Fire Technology Third Quarter 2001

warehouses and aircraft hangars. The model, which was developed in partnership with theCanadian Department of National Defence (DND), uses time-dependent, deterministicand probabilistic models to evaluate the impact of selected fire scenarios on life, propertyand business interruption. As part of this work, NRC has developed a computer modelto estimate water requirements for firefighting purposes for DND bases.

In this paper, commonly used methods to estimate firefighting water requirements arebriefly reviewed, along with some case studies, which demonstrate the need for a newwater requirements model. The theoretical basis for the new NRC water requirementsmodel is then described, as well as the use of the results of this model to estimate firedepartment equipment and human resources. The previous case studies are then used todemonstrate how this new model can be used to estimate required water flow rates forresidential, office and warehouse buildings. Future work and applications of the modelare also discussed.

Current Water Requirements Methods

Several methods are commonly used in Canada to estimate the required flow rate ofwater to extinguish fires in buildings. Five of the methods that are commonly used wereconsidered in this study:

• Insurance Services Office (ISO) Method �1�2�,• Iowa State University Method [3],• Illinois Institute of Technology Research Institute Method [2],• New Zealand Fire Engineering Design Guide Method [4], and• Fire Protection Water Supply Guideline for Part 3 in the Ontario Building Code

Method [5].

While there are other methods that have been previously discussed in the literature, thisliterature search was not meant to be exhaustive. Instead, methods were identified thatare commonly used by fire departments, and described in handbooks (e.g., [2]) or designguides (e.g., [4]). Another method, which is similar to the ISO and Ontario BuildingCode methods, can be found in NFPA 1142 [6], which deals with rural and suburbanareas where water must be transported to the scene of the fire from rivers, lakes, wells,cisterns or similar bodies of water. However, the method described in NFPA 1142 isoutside the scope of this paper, which deals with methods to estimate water requirementsfor DND bases, which are serviced by municipal water supplies. Therefore, only the firstfive methods are briefly described in the sections immediately below.

Insurance Services Office (ISO) Method

Current DND water requirements calculations are based on the Insurance Services Office(ISO) method, which calculates the needed fire flow (NFF) [1, 2]. The ISO method forestimating the required water flow rate for a building uses an equation that containsfactors that consider the building construction (C) and occupancy (O), adjacent exposedbuildings (X), and communication paths (P ) within buildings:

NFFi = �Ci�Oi�X+Pi (1)

Estimating Water Requirements 237

The ISO method outlines how each of the above factors are to be calculated (or lookedup in tables). The subscripts in the above formula indicate that, when different partsof a building have different characteristics, a factor can be calculated for each sectionand weighted according to the relative size of each section. This method also allowsthe required water flow rate to be reduced if the building is equipped with automaticsprinklers.

The ISO method is widely used and considers many important factors in its predic-tion of the required firefighting water flow for a building. Information is available onhow ISO arrived at the procedures used to determine some of the factors, such as theconstruction factor [7], however, this information is not available for some of the otherfactors. Also, the procedures to determine many of the factors require a considerableamount of experience and judgement.

Iowa State University Method

The Iowa State University method [3] is based on the amount of water which must beused to extinguish the fire by absorbing the energy of the fire and by displacing oxygen.Based on their research, Iowa State University determined that the volume of water, inlitres, required to extinguish a fire is equal to the volume of air in the building (V ), incubic metres, divided by 1.5. They also concluded that it is best if the total volume ofwater required to extinguish a fire is introduced into the burning area within 30 seconds,hence the required flow rate can be calculated using the following equation:

Flow Rate (L/min) = V

0�75(2)

This method is based on both empirical results and scientific principles. It assumesthat 80% of the water applied to the fire will be converted into steam, which may be toohigh for some scenarios. Some experts feel that, due to inefficiencies in the applicationof water, the actual water flow rate should be two to four times greater than that givenby Equation (2) [2]. Equation (2) is based on “normal” fuels (presumably cellulosic) andtherefore may not be appropriate for fires in industrial settings involving fuels that releasemore energy than cellulosic fuels. Therefore, some variations of this method change thevalue of the denominator based on the hazard associated with the occupancy [2]. As themodel only takes into account the volume of the building, it may produce inaccurateresults when applied to buildings with unusual geometry (e.g., high ceilings) or unusualfuel configurations. The model may also predict unrealistically high water flow rates forlarge fires, as it assumes that the total required volume of water is applied in 30 seconds.

Illinois Institute of Technology Research Institute Method

The formulae developed by the Illinois Institute of Technology Research Institute [2] arebased on a regression analysis of a survey of 134 fires in the Chicago area. The requiredwater flow rate for residential occupancies is given by the following equation:

Flow Rate (L/min)= 0�0395A2 +20�38A (3)


where A = the area of the fire (m2). The required water flow rate for non-residentialoccupancies is given by the following equation:

Flow Rate (L/min)=−5�7×10−3A2 +17�12A (4)

This method is based entirely on empirical data. Unfortunately, the details of the firesin the survey are not known, and so it is difficult to comment on this method. How wellthe results of the regression analysis of the 134 fires fit the actual data from the fires,and the method used to measure the water flow rates used to control these fires, are alsounknown.

New Zealand Fire Engineering Design Guide Method

This method [4] is based on the premise that the required flow rate of water is that whichwill be sufficient to absorb the energy of the fire. The required water flow rate is givenby the following equation:

Flow Rate (L/s)= Qf

�ab ·Qw

(5)

where

Qf = the heat release rate of the fire (MW),

�ab = the cooling efficiency, i.e., the efficiency of the water in absorbing theenergy from the fire �0 ≤ � ≤ 1, and

QW = the rate at which energy can theoretically be absorbed by the water(2.605 MW/L/s).

The cooling efficiency is a factor used to account for the fact that not all of the waterapplied to a fire will be converted to steam. The value of QW is based on the fact thatone litre of water will absorb 2.605 MJ of energy when it is heated from 0�C to steamat 100�C.

The accuracy of this method is dependent on the accuracy of the heat release ratedata and cooling efficiency value used. This method considers only the heat absorbingproperties of water and not the smothering effect of the steam produced when the wateris vaporized. This may result in a conservative estimate of the required water flow rate.

Fire Protection Water Supply Guideline for Part 3 in theOntario Building Code Method

The Ontario Building Code Method [5] was developed to provide a guideline for sat-isfying Code requirements for an adequate water supply for firefighting. The primarypurpose of the guideline is to provide an estimate of the amount of water requiredto support occupant evacuation and fire department search and rescue operations, andprevent exposure fire spread. The secondary purpose of the guideline is to provide anestimate of the amount of water required to provide a good measure of property pro-tection during the early stages of a fire. The method describes criteria to determine if a


building requires an on-site supply of water for fire protection. In cases where an on-sitesupply of water is required for fire protection, the required amount of water, (W , inlitres), is calculated using a formula that includes the volume of the building (V ) andfactors that consider the building occupancy and construction (K) and spatial separation(Stot):

W = KVStot (6)

The required water flow rate is determined by comparing this total required amount ofwater and the building area with various criteria. Flow rates calculated using this methodare between 1800 and 9000 L/min.

The Ontario Building Code method, like the ISO method, considers many importantfactors. However, as with the ISO method, information is not available on how the valuesof some of the coefficients and factors used in the method were obtained. Limitations ofthis method are clearly stated in its documentation [5]. When the building in question isnot sprinklered, and property protection is a primary concern or significant environmentalcontamination from a fire is possible, it is recommended that another method, such asthe ISO method, be used. The guideline is also not intended to address domestic servicewater needs, such as those in new development areas. Larger, more complex buildings,and buildings in rural areas may require larger amounts of water. In addition, once thecalculated value of the required water supply is greater than 270,000 L, the specifiedminimum flow rate is 9000 L/min, regardless of how large the building is. This methodmay therefore not be appropriate for very large buildings.

Discussion of Current Water Requirements Models

As discussed above, there are several methods that are commonly used to estimate therequired flow rate of water to extinguish fires in buildings. Of the five methods dis-cussed in the previous section, two methods (the Iowa State University method and theNew Zealand Fire Engineering Design Guide method) are based on first principles. Theother three methods (ISO method, Illinois Institute of Technology Research Institutemethod, and Ontario Building Code method) are based predominantly on empirical evi-dence. The ISO and Ontario Building Code methods are the most complete in termsof factors considered; however, the theory behind these methods is not completely clear.The Illinois Institute of Technology Research Institute method is an empirical correlationbased solely on 134 fires in the Chicago area. In order for such a method to be suitable,it needs to be based on a larger number of fires and be comprised of more than thetwo divisions (residential and non-residential buildings) present in the Illinois Instituteof Technology Research Institute method. The Iowa State University method does nottake into account many of the characteristics of different buildings and fires and the NewZealand Fire Engineering Design Guide method does not take into account all of themechanisms by which fires are extinguished. An important issue that is not consideredby any of the methods is that of fire control. The existing methods only consider theamount of water required for extinguishment. This produces unrealistic results for verylarge fires where fire extinguishment is impossible and the objective is to control the fire.


0

2000

4000

6000

8000

100 200

Floor Area (m2)

Wat

er F

low

Rat

e (L

/min

)

I

S

T

N

O

I

S

T

N

O

Figure 1. Comparison of current water requirements models –residential buildings. (I = Insurance Services Office, S = Iowa StateUniversity, T = Illinois Institute of Technology Research Institute,N = New Zealand Fire Engineering Design Guide, and O = OntarioBuilding Code.)

The five methods were used to estimate the firefighting water requirements for severalresidential, office and warehouse buildings of different sizes (Figures 1–3). It was foundthat there are large differences between the results using the different methods—in somecases, an order of magnitude difference in the predicted water flow rates. Estimates madeusing the New Zealand Fire Engineering Design Guide method were always larger thanthose made using the other methods, especially for the larger buildings. Some of the

0

5000

10000

15000

20000

25000

30000

500 2000 3000

Floor Area (m2)

Wat

er F

low

Rat

e (L

/min

)

I

S

T

T

O

S

N

O

I

S

T

N

O

I

N

Figure 2. Comparison of current water requirements models – officebuildings. (I = Insurance Services Office, S = Iowa State University,T = Illinois Institute of Technology Research Institute, N = New ZealandFire Engineering Design Guide, and O = Ontario Building Code.)


0

20000

40000

60000

80000

100000

120000

140000

160000

500 2000 3000

Floor Area (m2)

Wat

er F

low

Rat

e (L

/min

)

I S T

N

O I

S

T

N

O I

S

T

N

O

Figure 3. Comparison of current water requirements models –warehouse buildings. (I= Insurance Services Office, S = Iowa StateUniversity, T = Illinois Institute of Technology Research Institute,N = New Zealand Fire Engineering Design Guide, and O = OntarioBuilding Code.)

methods appear to be valid only for certain types and sizes of buildings. For example,the Illinois Institute of Technology Research Institute method appears to be invalid forlarger buildings, as the required water flow rates predicted by the model actually decreaseas the floor area gets large. Floor areas greater than approximately 1200 m2 appear tobe out of the useable range for this method.

It should also be noted that, as mentioned in the section describing the Iowa StateUniversity method, some have suggested that the estimates from this method should bedoubled or quadrupled. If this is done for the smaller buildings, the estimates madeusing the Iowa State University method will be considerably closer to estimates madeusing most of the other methods (e.g., Figure 1). For the larger buildings, estimatesmade using the Iowa State University method are already similar to the estimates madeusing most of the other methods, with the exception of the estimates made using theNew Zealand Fire Engineering Design Guide method (e.g., the 2000 and 3000 m2 officebuildings in Figure 2). Multiplying the estimates made using the Iowa State Universitymethod by two or four will therefore bring these estimates into closer agreement withthose made using the New Zealand Fire Engineering Design Guide method.

Methodology for New Water Requirements Model

As a result of the literature search and case studies described in this paper, the Fire RiskManagement Program of NRC has developed a new model for estimating water require-ments for firefighting purposes. This work was done in partnership with the CanadianDepartment of National Defence (DND), as part of the development of a computer modelto evaluate fire protection systems in light industrial buildings (FIERAsystem) [8]. Thenew model considers the geometry of the building, possible fire scenarios that may occur


in the building, fire detector locations and characteristics, the effect of automatic sup-pression systems on the fire, the locations of adjacent buildings, and the response andeffectiveness of the fire department.

The program calculates the required flow rates of water at the time of fire departmentintervention for suppression of the fire and for exposure protection for each side of thebuilding. These flow rates can then be compared with the total capacity of the fire enginesavailable to determine if existing resources are sufficient. The program has been designedto be interactive, so that the user can immediately see the effects of various parameterson the required water flow rate. For example, as the water requirement calculationsare dependent on fire department intervention time, the user can quickly determine theeffects of factors such as the location of fire halls, weather and traffic delays on waterrequirements.

The water requirements model is based on the following procedure:

1. determine the overall heat release rate curve for the building,2. determine fire detection and suppression system activation times,3. determine the effect of automatic suppression systems on the fire,4. determine the fire department intervention time,5. estimate the fire department effectiveness,6. calculate the thermal radiation heat fluxes to adjacent buildings,7. calculate the required flow rate of water for suppression of the fire,8. calculate the required flow rate of water for exposure protection, and9. calculate the total required flow rate of water for firefighting operations.

More details on the FIERAsystem submodels used in this program can be found inReference [8].

At each step, the user is given two options. The first option is to run a submodel todetermine the information needed by the main water requirements model. These sub-models are stand-alone pieces of software that are also used in FIERAsystem to evaluateindividual components of a fire protection system or to conduct hazard and risk analysesof buildings. The second option is to input the required data directly into the main waterrequirements model. For example, the user can run the detection submodel to determinethe time of sprinkler activation, or they can enter the activation time directly. In somesteps, there is also the option of using a datafile containing the results from other com-puter fire models or data from fire tests. This could be useful in analyzing a large numberof buildings in an area. For example, the heat release rate curve for a design fire could beused in place of running the fire development submodel for each building when planningan entire new community.

This methodology has been developed for implementation in a computer model thatuses FIERAsystem submodels to do water requirements calculations automatically. How-ever, the methodology can also be used with hand calculations and other models todetermine water requirements.

Determine Heat Release Rate Curve for Building

First, the user inputs information on the heat release rate curve (Qf�t) for the expectedfire scenarios in the building under consideration. This data can be entered directly or


imported from a datafile. The user also has the option of running FIERAsystem firedevelopment submodels, which will calculate the heat release rate curve based on thebuilding geometry, the fuels present in the building, and the selected fire scenarios.Models are currently available in FIERAsystem for the following fire scenarios:

• liquid pool fires,• storage rack fires, and• t2 fires (i.e., the heat release rate is assumed to be proportional to the square of the

elapsed time, which is often used to simulate fires).

The equations presently used in the fire development submodels are common fire protec-tion engineering correlations, such as t2 fires and other equations found in fire protectionengineering handbooks (e.g., [9]). Development of additional submodels that can be usedto simulate other fire scenarios of interest is ongoing.

Determine Fire Detection and Suppression System Activation Times

Next, the user can manually input the times from ignition until the fire is detectedand automatic suppression systems are activated. Alternatively, the user can run thefire detection submodel to determine the detection and activation times using the heatrelease rate curve entered or calculated in the previous step, the physical size of thefire and the location of the detector relative to the fire. Common fire protection engi-neering correlations are used to predict the temperatures and velocities at different loca-tions within the fire plume, ceiling jet and smoke layer (e.g., [9]). This information isthen used to calculate the time-dependent temperatures of all detection elements in thespace, based on their location relative to the fire. The time-dependent temperature ofeach detection element (or rate of temperature increase, for rate of rise detectors) canbe used to determine the activation time of each heat detector and sprinkler head inthe space.

Determine Effect of Automatic Suppression Systems on the Fire

Once, the activation time of the automatic suppression system has been entered or cal-culated, the effect of this system on the fire is determined. A suppression effectivenessvalue, �as, from 0 to 1.0, is entered, based on the ability of the automatic suppressionsystem to extinguish the fire scenario being considered. This effectiveness value is thenused to produce a modified heat release rate curve �Qm�t (Figure 4). It is assumed thatif the suppression system effectiveness is 1.0, the fire is controlled so that the heat releaserate of the fire remains at the heat release rate at the time of automatic suppression sys-tem activation (i.e., Qm = Qact). This assumption is conservative, as the sprinkler mayin fact extinguish the fire. If the effectiveness is 0, the heat release rate curve calculatedby the fire development model is not modified (i.e., Qm = Q0). If the effectiveness isbetween 0 and 1.0, the modified heat release rate is calculated at each time step usingthe following equation.

Qm = �1�0−�as · �Q0 −Qact+Qact (7)


0

100

200

300

400

500

0 20 40 60 80 100 120 140 160 180 200

Hea

tRel

ease

Rat

e(k

W)

Time (s)

Activation Time

= 0.0η

= 0.5η

= 1.0η

Figure 4. Correction of heat release rate using suppressioneffectiveness value, �.

Determine Fire Department Intervention Time

Next, the fire department intervention time is needed. This is the total time from thebeginning of the fire to the commencement of suppression by the fire department(Figure 5). The fire department intervention time is either entered by the user directly,or is calculated using the fire department response submodel. This submodel takesinto account the time required for detection (as calculated by the fire detection modeldescribed earlier or input by the user), notification, dispatch and preparation, travel andsetup. Calculations are based on factors such as the presence of fire alarms in the build-ing (and whether these are connected directly to the fire department), occupant response

Fire starts Fire is reported FD unit isnotified

FD unit leavesfire house

FD unit arrivesat scene of fire

Unit beginsfirefighting

activities

Fire isextinguished

NotificationTime

DispatchTime

PreparationTime

TravelTime

FirefightingTime

SetupTime

Intervention Time

Time

Response Time

Figure 5. Quantities used to calculate fire department (FD)intervention time.


to fire cues or other warning signals, the location of the building relative to the firedepartment, and preplanning.

Estimate Fire Department Effectiveness

The effectiveness of the fire department in suppressing the original fire and preventingignition of adjacent buildings is considered next. Two values are needed: �ab, an effec-tiveness of suppressing the fire, and �e, an effectiveness for exposure protection. Thevalues selected should be based on the specific techniques and equipment that firefight-ers use. For example, Särdqvist [10] lists values of �ab between 0.1 and 0.4 dependingon equipment and firefighting techniques used. The values selected should also takeinto account fire development at the time suppression commences, the nature of the firedepartment (professional, volunteer, or a combination of the two), and the amount offirefighter training and experience. Access to the fire in the building and access to theadjacent buildings for exposure protection should also be considered. At this time, valuesfor the effectiveness are input directly by the user. In the future the user will be ableto calculate these values using the fire department effectiveness submodel, as will bediscussed in the Future Work section.

Calculate Thermal Radiation to Adjacent Buildings

Thermal radiation heat fluxes from each side of the building to adjacent buildings arethen input. These can also be calculated by the radiation to adjacent buildings submodel.This submodel calculates thermal radiation heat fluxes with time, based on the occupancyof the building being considered and the fire resistance ratings of the exterior walls oneach side of the building. Thermal radiation heat fluxes to surrounding buildings alsoinclude the contributions of flames from combustible roofs.

The following method is used by the FIERAsystem radiation to adjacent buildingssubmodel to calculate incident heat fluxes to adjacent buildings. It should be noted thatthis method only considers thermal radiation heat transfer between the buildings. Absorp-tion and scattering of thermal radiation by the smoke and air between the burning andadjacent buildings is neglected. Convection heat transfer between the two buildings isneglected, which should be minor, especially at larger distances. Ignition of adjacentbuildings due to flying brands is also neglected.

The user supplies the following information to the model:

• the width �w and height �h of each of the exterior walls of the burning building• the number of floors above ground of the burning building,• the distance to the adjacent building �da on each of the four sides,• the fraction of unprotected openings �u on each of the four sides of the burning

building,• the time of failure of each of the four exterior walls of the burning building,• the critical heat flux �q′′

cr for each of the exposed walls of the adjacent buildings,• whether or not the building has a combustible roof and the failure time of the roof,

and• an assumed flame projection distance from the unprotected openings of the building�df.


The user first selects the equivalent heat fluxes at any unprotected openings in theburning building, q′′

o . While the user can input any equivalent heat flux value, one of twosuggested values can also be selected:

• 180 kW/m2 for an occupancy of “normal” hazard, or• 360 kW/m2 for an occupancy with a “severe” hazard.

These values form the basis for the tables for spatial separation and exposure protectionin the 1995 National Building Code of Canada (NBC) [11]. McGuire [12], examiningdata from the St. Lawrence Burns, noted that these heat flux levels were not exceededfor at least 16 minutes after any of these fire tests began. Sixteen minutes was thoughtto be greater than the length of time it normally takes a fire department to reach aburning building. However, heat fluxes up to five times these values were recorded after16 minutes in these tests. Therefore, for buildings where fire departments may take alonger time to respond, it may be appropriate to specify a larger equivalent heat fluxvalue when using this submodel.

Once the equivalent heat flux value is selected, the program calculates the radiationview factor between the unprotected openings and a point on the face of the adjacentbuilding based on the information provided by the user. Several assumptions are implicitin the formulae used here.

• Significant thermal radiation is only emitted from unprotected openings. A time-dependent fraction of unprotected openings is calculated for each of the four exteriorwalls, based on the time of failure of each of the walls and any combustible roof.

• The grey radiator concept is used to treat the unprotected openings �13�14�. This tech-nique assumes that the unprotected openings can be treated as one large unprotectedopening with the same area as the total of all the unprotected openings. The emissiv-ity for the burning building is then assumed to be the fraction of the exposing facadethat is unprotected openings. While this assumption is generally valid and producesconservative results, it is not always correct for buildings that have a low percentageof unprotected openings; in these cases different techniques can be used [14].

The view factor, F , for the unprotected openings, is calculated using the followingformula [13]

F = 2u

�

[√C/S

C/S+4arctan

√CS

C/S+4+√

CS

C/S+4arctan

√C/S

CS+4

](8)

where

u = the fraction of unprotected openings �0 ≤ u≤ 1,

C = hw

d2(9)

h = the height of the face of the burning building �m,


w= the width of the face of the burning building �m,d = is the “effective” distance (see below) between the burning and adjacent

buildings �m, and

S = h

w

(or

w

hif w > h

)�S > 1 (10)

The effective distance, d, is the actual distance between the buildings (da in Figure 6)minus the assumed distance that flames may project horizontally outside of the windowsof the burning building, df :

d = da −df (11)

a) Side View

b) Front View of Burning Building

hroof = Nh

h

w

uo

Assumed Locationof Flames on Roof

Burning Building

d

Unprotectedopenings

h

Adjacent buildingBurningbuildingwidth= w

df

Flameprojection

da

hroof = Nh

Figure 6. Quantities used for calculating view factor toadjacent building.


TABLE 1Values of N Used in Equation (12)to Estimate the Heights of Flameson a Roof

Number of Floors AboveGround in Burning Building N

1 1�42 0�93 0�734 0�655 0�586 0�52

The user can select an appropriate flame projection distance. For example, observationsmade during the St. Lawrence Burns indicated that values of df of 1.5 and 2.1 m maybe used for normal and severe hazards, respectively [12].

The fraction of unprotected openings for each exterior wall is calculated consideringthe time of failure of the wall and the time of failure of any combustible roof. When theexterior wall fails, it is assumed that the entire wall will act as an unprotected opening. Ifthe burning building has a combustible roof, then the flames on the burning roof will alsoact as an additional unprotected opening, once the roof fails, and will emit significantamounts of thermal radiation to adjacent buildings. In the preparation of NFPA 80A[15], photographs from thousands of fires were analyzed in order to see how high flamesprojected above the roofs of burning buildings. Using the information in NFPA 80A, thismethod assumes that any burning roof becomes an additional unprotected opening of areaequal to the width of the exterior wall of the building, w, multiplied by an estimatedflame height on the roof, hroof .

hroof = Nh (12)

where N is given in Table 1.The methods used to calculate the fraction of unprotected openings, u, and height,

h, for use in Equations (8)–(10) are listed in Table 2, and depend on whether theexterior wall or combustible roof fails first. These quantities are also illustrated inFigure 6.

Once the view factors, F has been calculated, the incident heat flux at the face of theexposed building, q′′

in can be found using

q′′in = Fq′′

o � (13)

Calculate the Required Flow Rate of Water for Suppression ofthe Fire

Based on the information entered in the steps outlined above, the amount of waterneeded to extinguish the fire is calculated based on the assumption that water can absorb


TABLE 2Techniques Used to Calculate the Fraction of UnprotectedOpenings and Height for Use in Equations (1)–(3)(uo = actual fraction of unprotected openings)

Combustible Roof Fails Prior to Exterior Wall Fails Prior toExterior Wall Combustible Roof

Fraction of Fraction ofUnprotected Openings Height Unprotected Openings Height

Time �u �h �u �h

Prior to any failure u= uo h u= uo h

After first building elementfailure u= uo+N

1+Nh�1+N u= u0 h

After both building elementshave failed u= 1�0 h�1+N u= 1�0 h�1+N

2.6 MW/L/s of flow, as discussed earlier in the section describing the New Zealand FireEngineering Guide. The required water flow rate to extinguish the fire is calculated usingthe formula given in the New Zealand Fire Engineering Guide [4]:

RFRab =Qm

�abQw

(14)

where

RFRab = the required flow rate of water to absorb the energy from the fire (L/s),

Qm = the heat release rate of the fire, modified to account for theeffectiveness of the suppression system (MW),

Qw = the rate at which energy can theoretically be absorbed bythe water (2.6 MW/L/s), and

�ab = the efficiency of the fire department in suppressing the fire �0≤ �ab ≤ 1.

The required flow rate of water is calculated as a function of time for the entire timeperiod for which heat release rate data is available. The value of the required flow rateat the time at which the fire department begins suppression will also be highlighted andused in subsequent calculations.

Calculate the Required Flow Rate of Water for Exposure Protection

The program also calculates water requirements for exposure protection using informa-tion on the heat fluxes to adjacent buildings entered by the user or calculated using theradiation to adjacent buildings submodel. The following equation is used to calculate therequired flow rate of water to prevent ignition of adjacent buildings.

�RFRei =�q′′

in−i −q′′minAa−i

�e−iQw

(15)


where

�RFRei = the required flow rate of water to prevent ignition of the adjacentbuilding on side i of the building being designed (L/s);

q′′in−i = the incident heat flux to the adjacent building on side i (MW/m2);

q′′min−i = the minimum heat flux for ignition of the exposed building

(MW/m2);

Aa−i = the exposed surface area of the adjacent building on side i (m2);

Qw = the rate at which energy can theoretically be absorbed by the water(2.6 MW/L/s); and

�e−i = the efficiency of the application of water by the fire department inpreventing ignition of the adjacent building on side i �0 ≤ �e−i ≤ 1.

It should be noted that this calculation will be time-dependent, as the heat fluxes toadjacent buildings will increase once fire resistance ratings are exceeded. The total valueof RFRe is the sum of the values of �RFRei for all of the sides of building beingevaluated.

Calculate the Total Required Flow Rate of Water forFirefighting Operations

If there are any special operations that required additional water, then the total requiredflow rate for these operations �RFRsp can be input by the user. The total estimatedrequired flow rate �RFRtot is then calculated using the following equation:

RFRtot = RFRab +RFRe +RFRsp (16)

Case Studies to Demonstrate the New Method

In order to demonstrate this new method, the required water flow rates were calculatedfor the residential, office and warehouse buildings discussed earlier. In all of the casestudies, it was assumed that the efficiency of water in suppressing the fire ��ab is 0.1,and that the efficiency of water in preventing ignition of adjacent building on each side i��e−i is 0.3. These values are consistent with the estimates made by Särdqvist [10]. Aswill be discussed later in the Future Work section, it is very difficult to determine theexact values to use for these two parameters. As the model is inversely proportional tothe suppression and exposure protection effectiveness values (Equations (14) and (15)),the choice of values has a large effect on the estimated water requirements.

Residential Buildings

The new model was used to estimate the water requirements for the residential buildingsused to compare the existing methods. The assumptions used in these case studies areshown in Table 3, along with a brief justification for each assumption. The design fire,compartment sizes, heat release rate density and other parameters were all selected to be


TABLE 3Values of Parameters used in Residential Case Studies as Inputs to NRCModel (single story residential building, 3 m high, no basement)

Property Value Reason for Assumed Value

Design fire Fast t2 fire Representative of fires in residential occupancies.

Size of room of 25–50% of total floor Based on dimensions used in previous case studies.fire origin area

Size of 25–50% of total floor Based on dimensions used in previous case studies.compartments to areawhich fire spreads

Heat release 500 kW/m2 floor area Recommended value for residential occupanciesrate density (NFPA 92B [16]).

Sprinklers None Worst-case scenario. Consistent with inputs used tocalculate water requirements using existing methods.

Fraction of 0.17–0.26 Consistent with inputs used to calculate waterunprotected requirements using existing methods.openings

Time of fire 15 minutes Representative of the failure time of interior walls inspread to adjacent residential buildings during actual fires.compartment

Heat flux to 12.5 kW/m2 prior to Maximum incident heat flux permitted inadjacent building failure of exterior wall most building codes.�q ′′

in 150 kW/m2 after failure Similar to values of equivalent heat fluxes atof exterior walls and boundaries of burning building for a normal hazard,roof and representative of maximum heat fluxes to

adjacent buildings after failure of exteriorwalls and roof of burning buildings.

Time of failure of 20 minutes Selected in order to study water requirementsexterior walls for exposure protection.

Time of failure of 30 minutes Selected in order to study water requirementsroof for exposure protection.

Fire department 15 minutes Based on typical notification, response and setupintervention time times in urban centers.

Size of exterior Same as exterior walls Typically building codes are based on informationwalls of adjacent of burning building on burning building and not adjacent buildings.buildings

consistent with the previous case studies and/or representative of residential occupancies.These values were then used to calculate the time-dependent heat release rate and otherquantities necessary to calculate the required water flow rates for firefighting operations.The maximum fuel controlled heat release rate was also compared with the maximumventilation controlled heat release rate, based on the amount of ventilation openings, toensure that there was sufficient oxygen to support this size of fire.

The individual times for the failure of interior walls, and the exterior walls and theroof were selected to be indicative of residential occupancies, and to also allow waterrequirements for exposure protection to be studied. In addition, as the location and dis-


tribution of windows were not specified in the earlier case studies, thermal radiation heatfluxes to adjacent buildings were not calculated explicitly. Instead, it was assumed thatthe incident heat flux from the unprotected openings to the neighbouring buildings isequal to 12.5 kW/m2. This is the generally accepted value of the minimum heat fluxnecessary to ignite wood, and is the basis of spatial separation requirements in mostbuilding codes. The heat flux once all of the exterior walls and roof fails was assumedto be 150 kW/m2, which is similar to the equivalent heat flux (q′′

o in Equation (13)) of180 kW/m2 used in many building codes (e.g., the National Building Code of Canada[11]). In between the failure of the exterior walls and the roof, the incident heat flux iscalculated by dividing 12.5 kW/m2 by the fraction of unprotected openings. The walls oneach side of the house are assumed to be the same size as those of the burning building.The fire department is assumed to begin suppressing the fire 15 minutes after it begins.This estimate is based on typical times for notification, dispatch, travel and set-up inurban areas. This time is used in lieu of calculating the components that make up thetotal intervention time separately (Figure 5).

Although the main purpose of these case studies was to demonstrate the use of thenew model, the estimates from the new model were compared with estimates madeusing the ISO, Iowa State University and the Illinois Institute of Technology ResearchInstitute methods. The latter three methods were chosen as they were considered to bethe most valid for residential buildings. Comparisons for houses with floor areas of 100and 200 m2 are shown in Figure 7. Required water flow rates estimated for various firedepartment intervention times for a house with a floor area of 200 m2 are shown inFigure 8.

Office Buildings

The new model was used to estimate the water requirements for the office buildings usedearlier to compare the existing methods. The assumptions used in these case studies are

0

1000

2000

3000

4000

5000

6000

7000

100 200

Floor Area (m2)

Wat

er F

low

Rat

e (L

/min

)

S S

T

INRC

NRC

T

I

Figure 7. Comparison of required water flow rates estimated usingthe new model (NRC), and the Insurance Services Office (I), Iowa StateUniversity (S) and Illinois Institute of Technology Research Institute (T)Methods for Various Residential Buildings.


0

50

100

150

200

250

0 10 20 30 40

Fire Department Intervention Time (min.)

Wat

er F

low

Rat

e (L

/min

)

Figure 8. Comparison of required water flow rate for various firedepartment intervention times for a house with a total floor area of200 m2.

shown in Table 4, along with a brief justification for each assumption. The design fire,compartment sizes, heat release rate density and other parameters were all selected tobe consistent with the previous case studies and/or representative of office buildings.These values were then used to calculate the time-dependent heat release rate and otherquantities necessary to calculate the required water flow rates for firefighting operations.The maximum fuel controlled heat release rate was also compared with the maximumventilation controlled heat release rate, based on the amount of ventilation openings, toensure that there was sufficient oxygen to support this size of fire.

The individual times for the failure of interior walls, and the exterior walls and the roofwere selected to be indicative of office buildings, and to also allow water requirements forexposure protection to be studied. Fire was assumed to spread to adjacent compartmentsin 30 minutes. Two exterior walls of the building were assumed to fail in 30 minutes,and the remaining two walls and the roof were assumed to fail in 40 minutes. This is dueto the fact that it will take some time for the fire to spread to all of the exterior walls,because of the size of the building. As with the residential case studies, the location anddistribution of windows were not specified and therefore thermal radiation heat fluxesto adjacent buildings were not calculated explicitly. Instead, it was assumed that theincident heat flux from the unprotected openings to the neighbouring buildings is equalto 12.5 kW/m2 initially, then once all of the exterior walls and roof fail, the heat fluxwas assumed to increase to 300 kW/m2. This latter value is similar to the equivalent heatflux (q′′

o in Equation (13)) of 360 kW/m2 used in many building codes (e.g., the NationalBuilding Code of Canada [11]) for more severe exposures than residential buildings. Inbetween the failure of the first two exterior walls and the remaining walls and the roof,the incident heat flux is calculated by dividing 12.5 kW/m2 by the fraction of unprotectedopenings. The walls on each side of the office building were assumed to be the same sizeas those of the burning building. The fire department was assumed to begin suppressingthe fire 15 minutes after it begins.

Estimates from the new model were compared with estimates made using the ISOand Iowa State University methods. The latter two methods were chosen as they were


TABLE 4Values of Parameters used in Office Building Case Studies as Inputsto NRC Model (four storey office building, each storey 3m high)


Design fire Fast t2 fire Representative of fires in office buildings.

Size of room of 25% of total floor area Based on dimensions used in previous case studies.fire origin

Size of 50% of total floor Based on dimensions used in previous case studies.compartments to areawhich fire spreads

Heat release 250 kW/m2 floor area Recommended value for offices (NFPA 92B [16]).rate density

Sprinklers None Worst-case scenario. Consistent with inputs used tocalculate water requirements using existing methods.

Fraction of 0.07 Consistent with inputs used to calculate waterunprotected requirements using existing methods.openings

Time of fire 30 minutes Representative of the failure time of interior walls inspread to adjacent office buildings during actual fires.compartment

Heat flux to 12.5 kW/m2 prior to Maximum incident heat flux permitted in mostadjacent building failure of exterior wall building codes.�q ′′

in 300 kW/m2 after failure Similar to values of equivalent heat fluxes atof exterior walls and boundaries of burning building for a severe hazard,roof and representative of maximum heat fluxes to


Time of failure of 30 minutes Selected in order to study water requirementsfirst two exterior for exposure protection.walls

Time of failure of 40 minutes Selected in order to study water requirementsremaining two for exposure protection.exterior wallsand roof



considered to be the most valid for office buildings. The Illinois Institute of TechnologyResearch Institute method was not used here as it was shown in the earlier case studiesthat this building is larger than the buildings that this method is applicable for. Com-parisons for office buildings with floor areas of 500, 1000 and 2000 m2 are shown inFigure 9. Required water flow rates estimated for various fire department interventiontimes for an office building with a floor area of 200 m2 are shown in Figure 10.


0

5000

10000

15000

20000

500 2000 3000

Floor Area (m2)

Wat

er F

low

Rat

e (L

/min

)

I

S

NRC

I

S NRC

I

S

NRC

Figure 9. Comparison of required water flow rates estimated usingthe new model (NRC), and the Insurance Services Office (I) and IowaState University (S) Methods for Various Office Buildings.

Warehouse Buildings

The new method was also used to estimate the water requirements for the warehousebuildings described earlier. The assumptions used in these case studies are shown inTable 5, along with a brief justification for each assumption. The design fire, compartmentsizes, heat release rate density and other parameters were all selected to be consistentwith the previous case studies and/or representative of warehouse buildings. These valueswere then used to calculate the time-dependent heat release rate and other quantitiesnecessary to calculate the required water flow rates for firefighting operations. For the

0

20000

40000

60000

80000

100000

0 10 20 30 40 50 60

Fire Department Intervention Time (min)

Wat

er F

low

Rat

e (L

/min

)

Figure 10. Comparison of required water flow rate for various firedepartment intervention times for an office building with a total floorarea of 2000 m2.


TABLE 5Values of Parameters used in Warehouse Building Case Studies asInputs to NRC Model (single story residential building, 10m high)


Design fire Ultrafast t2 fire Representative of fires in warehouses.

Size of room of 50% of total floor Based on dimensions used in previous case studies.fire origin area

Size of 50% of total floor Based on dimensions used in previous case studies.compartments to areawhich fire spreads

Heat release 1000 kW/m2 storage Representative of fuels in warehouse buildings-storagerate density area area for fuel assumed to 50% of total floor area

of room of fire origin.

Sprinklers None Worst-case scenario. Consistent with inputs usedto calculate water requirements using existing methods.

Fraction of 0.16 About one-half of value used in earlier case studies.unprotected Representative of value of warehouse buildings,openings assuming some loading doors open.

Time of fire 45 minutes Representative of the failure time of interior walls inspread to adjacent warehouses during actual fires.compartment

Heat flux to 12.5 kW/m2 prior to Maximum incident heat flux permitted in mostadjacent building failure of exterior wall building codes.�q ′′

in 300 kW/m2 after failure Similar to values of equivalent heat fluxes atof exterior walls and boundaries of burning building for a severe hazard,roof and representative of maximum heat fluxes to


Time of failure of 30 minutes Selected in order to study water requirementsfirst two exterior for exposure protection.walls

Time of failure of 40 minutes Selected in order to study water requirementsremaining two for exposure protection.exterior wallsand roof



purposes of this calculation, it was assumed that material is only stored over half of thefloor area of the warehouse. Therefore, the maximum fuel controlled heat release ratefor the original fire was calculated by multiplying the heat release rate density by 25%of the total area of the building. The maximum fuel controlled heat release rate wasalso compared with the maximum ventilation controlled heat release rate, based on theamount of ventilation openings, to ensure that there was sufficient oxygen to support thissize of fire.


0

40000

80000

120000

160000

0 10 20 30 40 50 60

Fire Department Intervention Time (min)

Wat

er F

low

Rat

e (L

/min

)

Total

Suppression

Exposure Protection

Figure 11. Comparison of required water flow rate for various firedepartment intervention times for a warehouse with a total floorarea of 2000 m2—Total water requirements, and the componentsfor suppression and exposure protection.

Individual times for the failure of interior walls, and the exterior walls and the roofwere selected to be indicative of warehouse buildings, and to also allow water require-ments for exposure protection to be studied. Fire was assumed to spread to adjacentcompartments in 45 minutes. Two exterior walls of the building were assumed to failin 30 minutes, and the remaining two walls and the roof were assumed to fail in 40minutes. This is due to the fact that it will take some time for the fire to spread toall of the exterior walls, because of the size of the building. As with the previous casestudies, the location and distribution of windows were not specified and the thereforethermal radiation heat fluxes to adjacent buildings were not calculated explicitly. Theincident heat fluxes were calculated in the same manner as for the office buildings, andthe walls on each side of the warehouse were again assumed to be the same size as thoseof the burning building. The fire department was assumed to begin suppressing the fire15 minutes after it begins.

As shown in the earlier case studies, there were huge differences in the predictionsmade using existing methods for warehouses. Therefore, estimates from the new modelwere not compared directly with any of the existing methods. Required water flowrates estimated for various fire department intervention times for a warehouse witha floor area of 2000 m2 are shown in Figure 11. These water flow rates are furtherdivided into the amounts required for suppression (Equation (14)) and exposure protec-tion (Equation (15)).

Discussion

While the main purpose of the case studies, was to demonstrate the model, rather thanto compare its estimates with other models, the predictions made using the NRC modelare similar to those made using the ISO and Illinois Institute of Technology ResearchInstitute methods for the residential buildings studied (Figure 7). The predictions madeby the NRC and the two existing models are considerably different from those madeusing the Iowa State University method, as the Iowa State University method only takes


into account the volume of the building, and not any other factors considered by theother methods.

It is difficult, however, to draw concrete conclusions from these comparisons. Valuesof the parameters shown in Table 3 were chosen to be similar to those used in the earliercase studies. However, the new model considers a much larger number of parameters thanthe existing model. Nevertheless for this choice of parameters, this study does indicatethat estimates made using the new model are at least comparable to those which firedepartments would make using commonly used methods today.

The NRC model has the advantage of being able to take into account the fire depart-ment intervention time. In the case of the residential buildings, the water requirementspredicted by the NRC model are similar to those predicted using the ISO or Illinois Insti-tute of Technology Research Institute method, if a typical fire department interventiontime in urban centres, 15 minutes, is assumed. However, Figure 8 shows that for isolatedcommunities, the required flow rate can increase quickly, as this flow rate is directlyproportional to the heat release rate (Equation (14)), which is assumed to be directlyproportional to the square of the elapsed time in these case studies. On the other hand,a shorter intervention time will result in a smaller required flow rate. While this conceptis well known qualitatively, tools such as the NRC model will allow fire departments toquantify the effects of intervention time on required water flow rate. Areas in which thisinformation can be used will be discussed in the next section of this paper.

The predictions made using the NRC model are similar to those made using the ISOmethod for the 500 m2 office building, and are similar to those made using the Iowa StateUniversity method for the 2000 m2 office building (Figure 9). The water requirementspredictions made by both existing methods are substantially larger than those madeusing the NRC model for the 3000 m2 office building. This is because the flow ratespredicted by the NRC model for a 15 minute fire department intervention time are basedcompletely on the water required for suppression, as no external walls will have failed atthis time. Other than the 500 m2 building, the heat release rate in the compartment of fireorigin did not reached its maximum value (based on the size of the compartment and theventilation openings) for a fire department intervention time of 15 minutes. Therefore,the heat release rates, and hence the water flow rate predictions are the same for boththe 2000 and 3000 m2 buildings. On the hand, the predictions made by the two existingmodels are dependent on the size of the building, and hence increase as the buildingfloor area increases. For longer fire department response times, after the fire spreads toother compartments and the exterior walls fail, the size of the building will have a largereffect on the predictions made using the NRC model (Figure 10). This illustrates howthe NRC model is able to take into account features, such as compartmentation and fuelloads, explicitly in its calculations.

As mentioned earlier, there are huge differences in the predictions made using existingmethods for warehouses, and therefore, estimates from the new model are not compareddirectly with any of the existing methods. Figure 11 shows how the required water flowrate, which for suppression is directly proportional to the heat release rate calculated foran ultrafast t2 fire, increases very rapidly for a warehouse. In addition, as the floor areasand ventilation openings in the warehouse are very large, the maximum heat releaserates for these buildings, and hence the required water flow rates, will be very large.Depending on the expected intervention time, fire departments may wish to examine the


estimates for the water requirements for suppression and exposure protection separately,and determine whether an offensive attack will be possible using the equipment andpersonnel available, or whether the department will concentrate on exposure protection.Figure 11 also helps to emphasize the importance of detection and suppression systemsin warehouses. A detection system that can significantly reduce intervention time and asuppression system that can maintain or reduce the heat release rate of the fire when itis activated will both have a large effect on water requirements for firefighting. Again,while these effects are well known qualitatively, tools such as the NRC model can helpto demonstrate these effects quantitatively, as well as assisting in the design of detectionand suppression systems.

Applications of the NRC Model

The results from the NRC model, when combined with information on the equipmentand human resources available to a fire department, will allow a number of analyses to beperformed. Initial and subsequent responses to individual buildings and/or communitiescan be planned, based on possible fire scenarios in these buildings and/or communities.The interactive nature of the program is designed to allow planners to perform “what if”calculations when determining their equipment and human resources requirements. Inputdata, such as information on the building design or the times used to calculate the firedepartment intervention time, can be changed in order to determine how these changesaffect water requirements.

Urban planners could also use the model for determining the optimal locations of firestations. Studies could also be performed to determine how mandatory sprinklers in res-idential buildings affect the locations of fire stations in a community. As a major factorin sizing water mains is providing sufficient water flow rates for firefighting operations,the new model should also be of interest to those designing new water lines or rehabili-tating existing water lines. As many water lines are in the need of repair or replacementin the near future, models that can provide information on the required flow rates forfirefighting are becoming increasingly important to municipalities around the world.

Conclusions and Future Work

There are a limited number of existing methods to estimate required flow rates of waterfor firefighting purposes, and there are large differences between the results predicted bythese methods. A new water requirements model developed by the Fire Risk ManagementProgram of the National Research Council of Canada, for use on Canadian DND bases,has been briefly described. This water requirements model is designed to be used inconjunction with submodels from FIERAsystem, a computer model used to evaluate fireprotection systems in light industrial buildings, or as a stand-alone piece of software.Input data from other sources, such as fire test data or heat release rate curves for designfires, can also be used by the water requirements model.

Future work is ongoing to improve the water requirements model. Research is beingconducted to determine appropriate values for some of the factors used in these calcu-lations, such as the suppression and fire department effectiveness values. As mentionedearlier, this is very important, as currently there is no method of calculating these values,


and water requirements estimates are inversely proportional to these values. While somevalues have been estimated from laboratory tests, it is necessary to determine values foractual firefighting. In many cases, efficiency values will be much lower, for a numberof reasons, including reduced visibility and in many cases, the inability to get to theseat of the fire. As well as identifying how to calculate these and other parameters usedin the model, it will also be important to conduct sensitivity studies to determine howvariations in each individual parameter will affect water requirements estimated usingthis methodology. This work will be done for many of the individual submodels as partof the development of FIERAsystem.

Further case studies are being conducted to compare the required flow rates predictedby this model with those predicted using existing methods for actual DND buildings. Theuser interface for the program will be improved based on the results of field trials of thissoftware by DND and municipal fire departments. This interface work will also includeadding the capability of calculating equipment and human resource requirements forspecific buildings based on calculated water flow rates. Work is also ongoing to improvethe FIERAsystem submodels included in the water requirements program and to developadditional fire development submodels to simulate other fire scenarios of interest. Theprogram will also be modified for use by urban planners in sizing water mains.

Acknowledgements

The authors wish to acknowledge the hard work and efforts of the entire team responsi-ble for the development of both this computer program and FIERAsystem: Dr. ZhumanFu, Ping Feng, Henry Hum, Joe Hum, Neil Pilgrim, Dr. Don Raboud, Irene Reid, WeiSu, Martin Will and Brent Yager. Assistance from the FIRECAMTM team, includingCharles Dutcher, Dr. Guylène Proulx, and Dr. David Yung is also gratefully acknowl-edged. Financial assistance for this project from the Canadian Department of NationalDefence is also gratefully acknowledged, along with the assistance and feedback pro-vided by Major Barry Colledge and Captain Steve Vollhoffer.

Notes1. Now with the Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Dr.,

Saskatoon, SK S7N 5A9.2. Now with the Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel By

Drive, Ottawa, ON K1S 5B6.

Nomenclature

A area (m2)C building construction factor (L/s or L/min)

ratio of product of height and width to distance squared (dimensionless)d distance (m)F radiation view factor (dimensionless)h height (m)K building occupancy and construction factor (dimensionless)


N factor to account for flames from a roof (dimensionless)NFF needed fire flow (L/s or L/min)O occupancy factor (dimensionless)P communication paths factor (dimensionless)Q heat release rate or energy absorption rate (kW)q′′ heat flux (kW/m2)RFR required flow rate (L/s or L/min)S spatial separation factor, ratio of height to width (dimensionless)t time (s)u fraction of unprotected openings (dimensionless)V volume (m3)W amount of water (L)w width (m)X adjacent exposed buildings factor (dimensionless)

Greek letter

� efficiency of water application (dimensionless)

Subscripts

a adjacentab absorptionact at time of activation of automatic suppression systemas automatic suppression systemcr criticale exposure protectionf fire, flamei indexin incidentm modifiedmin minimumo originalroof roofsp special operationstot totalW water0 value with no automatic suppression system

References[1] G.C. Anderson, “ISO Commercial Risk Services,” AWWA Seminar Proceedings—Fire Pro-

tection, American Water Works Association, Denver, CO, June, 1986.[2] K.W. Linder, “Water Supply Requirements For Fire Protection,” Fire Protection Handbook,

17th ed., Quincy, MA: National Fire Protection Association, 1981.[3] K. Royer, W.N. Floyd, “Water For Fire Fighting—Rate-of-Flow Formula,” Iowa State Uni-

versity Bulletin, Engineering Extension—Bulletin No. 18, Iowa State University, Ames, IA.[4] A.H. Buchanan, (ed.), Fire Engineering Design Guide, Centre for Advanced Engineering,

University of Canterbury, New Zealand, 1994.


[5] “Fire Protection Water Supply Guideline for Part 3 in the Ontario Building Code,” Office ofthe Fire Marshal Technical Guideline OFM-TG-07-96, Province of Ontario, North York, ON,1996.

[6] NFPA 1231: Standard on Water Supplies for Suburban and Rural Fire Fighting, Quincy, MA:National Fire Protection Association, 1993.

[7] K.J. Carl et al., “Guidelines For Determining Fire-Flow Requirements,” Journal of theAmerican Water Works Association, May 1973, pp. 335–344.

[8] G.V. Hadjisophocleous, D.A. Torvi, Z. Fu, and B. Yager, “FIERAsystem: A Computer Modelfor Fire Evaluation and Risk Assessment,” Proceedings, ASME Offshore Mechanics and Arc-tic Engineering (OMAE) 18th International Conference, July 11–16, 1999, St. John’s, NF,Paper Number OMAE99-6016.

[9] SFPE Handbook of Fire Protection Engineering, Quincy, MA: National Fire Protection Asso-ciation, 1995.

[10] S. Särdqvist, An Engineering Approach to Fire-Fighting Tactics, Report 1014, Department ofFire Safety Engineering, Lund University, Sweden, 1996.

[11] National Building Code of Canada 1995, Canadian Commission on Building and Fire Codes,National Research Council of Canada, Ottawa, ON, 1995.

[12] J.H. McGuire, “Fire and the Spatial Separation of Buildings,” Fire Technology, vol. 1, 1965,pp. 278–287.

[13] G. Williams-Leir, “Approximations for Spatial Separation,” Fire Technology, vol. 2, 1966,pp. 136–145.

[14] G. Williams-Leir, “Another Approximation for Spatial Separation,” Fire Technology, vol. 6,1970, pp. 189–202.

[15] NFPA 80A: Recommended Practice for Protection of Buildings from Exterior Fire Exposures,Quincy, MA: National Fire Protection Association, 1993.

[16] NFPA 92B: Guide for Smoke Management Systems in Malls, Atria, and Large Areas, Quincy,MA: National Fire Protection Association, 1995.

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