NISTIR 4833 

A Sprinkler Fire Suppression Algorithm 

for the GSA Engineering Fire Assessment System 

Daniel Madrzykowski 

Robert L. Vettori 

US. Department of Commerce 

National Institute of Standards and Technology 

Building and Fire Research Laboratory 

Gaithersburg, MD 20899 

Prepared for: 

General Services Administration 

Public Buildings Service 

Office of Real Property Management and Safety 

Washington, DC 20405 
NISTIR 4833 

A Sprinkler Fire Suppression Algorithm 

for the GSA Engineering Fire Assessment System 

Daniel Madrzykowski 

Robert L. Vettori 

May 1992 

U.S. Department of Commerce 

Barbara Hackman Franklin, Secretary 

Technology Adminstration 

Robert M. White, U'emecretary of Techn, 1 

Prepared for: 

General Services Administration 

Richard G. Austin, Administrator 

Public Buildings Service 

Milton Herson, Commissioner 

Office of Real Property Management and Safety 

Washington, D.C. 20405 

National Institute of Standards and Technology 

John W. Lyons, Director 

Building and Fire Research Laboratory 

Gaithersburg, MD 20899 
TABLE 0.F CONTENTS 

Page 

LISTOFTABLES ...................... 

LISTOFFIGURES ....................... 

ABSTRACT .......................... 

1 . BACKGROUND ....................... 

2 . APPROACH ........................ 2.1 SUPPRESSION OF WOOD CRIB FIRES .......... 

3 . EXPERIMENTAL APPROACH 0 

3.1 SELECTION OF FUEL PACKAGES ............ 3.2 IGNITION SOURCES ................. 3.3 HEAT RELEASE RATE MEASUREMENT 

3.4 METHOD OF WATER APPLICATION ............ 

4 TEST PROCEDURE 0 . . e 

4.1 SOFA FUEL PACKAGE ................. 

4.3 OFFICE FUEL PACKAGE ................ 4.4 WORK STATION I FUEL PACKAGE 

4.5 TRASH CART FUEL PACKAGE .............. 4.6 WORK STATION I1 FUEL PACKAGE ............ 4.7 PAPER RECYCLING CART FUEL PACKAGE ......... 4.8 EXECUTIVE DESK FUEL PACKAGE ............ 4.9 OFFICE I1 FUEL PACKAGE ............... 4.10 SECRETARIAL DESK FUEL PACKAGE ........... 

4.2 CHAIR FUEL PACKAGE 

5 . HEAT RELEASE RATE REDUCTION FACTOR FOR FURNISHINGS . . 5.1 SPRINKLERED FIRE SUPPRESSION ALGORITHM ..... 

6 . DISCUSSION ...................... 

7 . CONCLUSIONS ...................... 

8 . ACKNOWLEDGEMENTS ................... 

iv 

V 

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2 

2 

2 

6 

6 

7 

7 

7 

8 

8 

9 

9 

9 

9 

10 

10 

11 

12 

13 

9 . REFERENCES ...................... 

iii 

13 
LIST OF TABLES 

Page 

15 

16 

17 

18 

19 

20 

Table 1. Office Fuel Package Components . . . . . . . . . 

Table 2. Work Station I Fuel Package Components . . . . . 

Table 3. Work Station I1 Fuel Package Components . . . . . 

Table 4. Executive Office Fuel Package Components . . . . 

Table 5. Office I1 Fuel Package Components . . . . . . . . 

Table 6. Secretarial Desk Fuel Package Components . . . . 

iv 
LIST OF FIGURES 

Page 

Figure 1. Wooden Crib Fuel Package ........... 21 

Figure 2. Heat Release Rate Curves - Wooden Crib Fuel 

Package ................... 22 

Figure 3. Normalized Heat Release Rate Curves - Wooden Crib 

Fuel Package ................. 23 

Figure 4. Typical Test Configuration ......... 24 

Figure 5. Average Water Spray Density .......... 25 

Figure 6. Sofa Fuel Package .............. 26 

Figure 7. Heat Release Rate Curves - Sofa Fuel Package . . 27 

Figure 8. Office Fuel Package .............. 28 

Figure 9. Heat Release Rate Curves - Office Fuel Package 29 

Figure 10. Work Station I Fuel Package ......... 30 

Figure 11. Heat Release Rate Curves - Work Station I Fuel 

Package .................. 31 

Figure 12. Work Station I1 Fuel Package ........ 32 

Figure 13. Heat Release Rate Curves - Work Station I1 Fuel 

Package ................... 33 

Figure 14. Heat Release Rate Reduction Curves - Paper 

Recycling Cart, Office 11, Executive Desk and 

Secretarial Desk Fuel Packages 0.. 0.0. 34 

Figure 15. Envelope of Normalized Heat Release Rate Curves 

with HRR Reduction Curve .......... 35 

V 
A Sprinkler Fire Suppression Algorithm for the GSA 

Engineering Fire Assessment System 

Daniel Madrzykowski 

Robert L. Vettori 

Building and Fire Research Laboratory 

National Institute of Standards and Technology 

ABSTRACT 

A study was conducted to develop a sprinkler fire suppression 

algorithm for use with sprinkler activation time models. Large 

scale experiments were performedto determine the heat release rate 

(HRR) of selected office fuel packages with and without sprinklers 

operating. Eight different fuel packages were evaluated. The 

results from these experiments were used to develop a time 

dependent HRR reduction factor. 

HRR R e d u c t i o n F a c t o r - 

where: t - Time after sprinkler 

activation (s) 

The sprinkler fire suppression algorithm consists of multiplying 

the HRR reduction factor by the HRR at the time of sprinkler 

activation, Qact, yielding an expected upper bound to the HRR at a 

given time after sprinkler activation, Q(t) I for office furnishing 

fires that are not heavily shielded. 

This sprinkler fire suppression algorithm can be thought of as a 

!?zeroth ordert1 fire suppression model for "light hazard" 

occupancies with a sprinkler spray density of 0.07 mm/s (0.1 

gpmift2) or greater . 

Key words: crib fires; fire suppression; fire tests; fuel load: 

free burning fires; heat release rate: sprinklers 

1 
1. BACKGROUND 

The General Services Administration (GSA) has expressed a need for 

sprinkler design criteria for use in government office spaces which 

ensure adequate, cost effective fire protection. Under the 

sponsorship of GSA, the Building and Fire Research Laboratory 

(BFRL) at the National Institute of Standards and Technology (NIST) 

has conducted several studies related to the use of sprinkler 

systems in occupancies of interest to GSA. These studies have 

included 1) demonstrating the applicability of quick response 

sprinklers in off ices [ 1 J I, 2) determining the effect of sprinkler 

sprays on the burning rate of idealized fuels[2], and 3) examining 

the conditions affecting the operation of sprinklers[3]. 

Concurrent with these studies, an engineering fire assessment 

system, FPETOOL[4], has been developed to evaluate hazard and fire 

protection strategies in GSA buildings. Although this assessment 

system can be used to evaluate a wide range of conditions, it does 

not specifically address the benefits of sprinklers. The system is 

capable of predicting the time of operation of sprinklers. The 

inclusion of a sprinklered fire suppression calculation in the 

assessment system would provide a significant advance in 

capability. The objective of this study was to develop a 

sprinkler fire suppression algorithm for office furnishings for 

inclusion in FPETOOL. 

2. APPROACH 

Office furnishings and equipment can be composed of forms of wood, 

plastic, foam, textiles and any combination thereof. The geometry 

of most furnishings is such that some surfaces would be exposed to 

direct impingement from a sprinkler's water spray and other 

surfaces would be shielded from the water spray. As furnishings 

may be ignited in various positions, and the initial flame spread 

is also variable, it is likely that geometry effects could cause a 

great variation in fire suppression of furnishings. A priori 

predictions of the reduction of heat release rate (HRR) during 

suppression of furnishing fires, even if the position of ignition 

is specified, is well beyond present engineering capabilities. As 

a first step, a sprinkler fire suppression algorithm that consists 

of a bounding curve defined by a simple functional form has been 

developed based on experimental data. 

2.1 SUPPRESSION OF WOOD CRIB FIRES 

In a previous study for GSA, Walton [2] provided information on the 

reduction in HRR as a function of water spray density on wood crib 

fires. Wood cribs were used because they provide a repeatable 

source fire. In addition, portions of cribs are shielded from the 

Numbers in brackets indicate literature references at the 

end of the paper. 

2 
water spray, while other portions are fully exposed (Figure 1). 

Wood cribs are representative of light hazard fuel packages. 

Figure 2 shows the suppression of fully involved, well ventilated 

45 kg (100 lb) wood crib fires, at six different water spray 

densities. The two extremes are represented by the non-sprinklered 

curve, in which no water spray was applied and the 0.126 mm/s 

(0.186 gpm/ft2) water spray density curve which reduced the HRR 

rate by 60% within one minute of sprinkler activation. 

For purposes of sprinkler system design, an office space is 

considered a light hazard occupancy by NFPA 13[5]. For calculating 

water demand this standard specifies a minimum 0.07 mm/s 

(0.1 gpm4ft2) for light hazard occupancies of 135 m2 

(1500 ft) or less in floor area. 

The HRR curves in Figure 2 for two of the experiments are in the 

approximate range of this minimum water spray density, 0.066 mm/s 

(0.097 gpm/ft2) and 0.081 mm/s (0,119 gpm/ft2). For these crib 

fires that were in the quasi-steady burning rate period at the time 

of sprinkler operation, the fire suppression effect of the 

sprinkler spray on the burning fuel may be characterized by the 

reduction in HRR relative to HRR at the time of sprinkler 

activation. By dividing the two data sets listed above by their 

respective HRR at the time of sprinkler activation and graphing 

this data on a semi-log chart (Figure 3) it can be seen that they 

are almost linear, indicating that the HRR after sprinkler 

activation may be represented by an exponential function of time. 

Curve fitting the average of the two tests yields the following 

equation : 

-0.00225 ( t- tact) HHRReduction - 0.73 x e 

where: tact - Time at sprinkler 

activation (s) 

In Figures 2 and 3, tact is equal to 0. 

3. EXPERIMENTAL APPROACH 

Fuel packages of typical office furnishings and equipment were 

selected and burned to determine their heat release rate 

characteristics. Then similar fuel packages were ignited and 

suppressed with a water spray from a sprinkler to determine the 

reduction in heat release rate. The ignition scenarios for these 

fuel packages were based on waste basket fires or improper disposal 

of smoking materials. 

3 
3.1 SELECTION OF FUEL PACKAGES 

A physical survey was taken of furnishings at GSA's Central Office 

in Washington D.C. Several categories of furnishings or fuel 

packages were identified. The first category of fuel was made up 

of sofas and upholstered chairs which were typically found in 

reception areas or executive suites. The second category of fuel 

consisted of furnishings of wooden construction; a desk, a 

reference table and a padded wood frame desk chair. These 

furnishings were usually complemented by a computer terminal and 

assorted paper products. This category of fuel is identified as 

the office scenario. The third category of fuel package was 

identified as a work station. The work stations were composed of 

partitions and laminated wood composite work surfaces with metal 

support structures. An ABS plastic "tub chairvv, a computer 

terminal, and a paper product load similar to that used in the 

office scenario completed the work station fuel package. 

It was noted during the building walk through that there was an 

extensive use of cardboard boxes for file storage under desks and 

other horizontal work surfaces. This fuel would be shielded from 

the sprinkler spray. To simulate this condition, four "copier 

paper cardboard boxes," each containing twenty pounds of paper, 

were used as a shielded fire load in the office and the work 

station test scenarios. 

The last category ~~ of fuel packages was made up of trash carts and 

paper recycling carts. These four fuel package categories seemed 

to cover the majority of the furnishings found in the GSA Central 

Office Building. 

Similar furnishing items were procured fromthe GSA surplus center 

for use in this study. Finding matching furnishings limited the 

number of experiments which could be performed in some cases. For 

instance only two sofas could be located which had the same 

upholstery (Le., fabric and padding) and the same shape. 

Comparable desks and tables were of identical construction and 

finish with the possible exceptions of drawer configuration or leg 

shape . Comparable chairs and partitions were of identical 

construction, respectively, with the possible exception of fabric 

color . Inoperative computer terminals and waste paper were 

obtained at NIST for use in this study. Loading the furnishings 

with a paper load representative of that found during the survey 

yielded a loading of 50.5 kg/m2 (10 lbs/ft2) on the 5.9 m2 (64 ft2) 

load cell. 

3.2 IGNITION SOURCES 

All of the furniture fuel packages were ignited with a natural gas 

diffusion flame. The burner was a rectangular shaped, open top 

4 
steel box, 250 mm (9.75 in) long, 185 nun (7.25 in) wide and 

70 mm (2.75 in) deep. The shell of the burner was filled with 

sand, covered by a fibrous refractory material and topped with 

expanded metal. The top of the burner was located 380 mm (15 in) 

above the surface of the load platform to represent the height of 

a trash can. The burner was operated at 50 kW for 200 seconds to 

simulate a small trash can fire as defined by Babrauskas[6,7]. 

The paper recycling cart and the trash cart fuel packages were 

ignited with an electric match positioned approximately half-way up 

from the bottom of the cart, in between the bags of paper. This 

scenario was intended to represent ignition cased by improper 

disposal of smoking materials. 

3.3 HEAT RELEASE RATE MEASUREMENT 

The tests were performed under an instrumented exhaust hood which 

provides measurements of heat release rate (Figure 4) . The heat 

release rate is measured by the method of oxygen consumption 

calorimetry[8]. The method of oxygen consumption calorimetry 

requires that all of the gaseous combustion products from the 

burning item flow through a duct where the mass flow rate and the 

oxygen concentration are measured. In this study, measurements 

were made at approximately 11 second intervals via a computerized 

data collection system. A burn was conducted with selected fuel 

packages to provide heat release rate data without any suppression 

action for comparison purposes. 

3.4 METHOD OF WATER APPLICATION 

To ensure that the water spray used in the suppression tests was 

representative of sprinkler sprays found in practice, a 

commercially available pendent sprinkler head was employed. The 

sprinkler head deflector was located 2.35 m (93 in) above the 

surface of the load platform as if installed below a 2.44 (8 ft) 

ceiling, except no ceiling was present. The sprinkler's position 

relative to the fuel packages varied depending on the type of fuel 

package. The flow from the sprinkler was fixed at 1.6 x m3/s 

(25 gpm) for all of the experiments. 

To determine the amount and the distribution of the water spray on 

the load platform, 0 36 m (14 in) square pans were placed adjacent 

to one another on the load platform to collect the water spray for 

a fixed period of time, usually 10 minutes. The amount of water in 

each pan was measured and recorded to develop a spray density map 

of the load platform. Areas on the platform had spray densities as 

low as 0.035 m/s (0.052 gpm/ft2) and as high as 0.13 mm/s 

(0.18 gpm/ft2) . It has been shown that sprinkler spray density 

varies widely[2,9], so it was not surprising to see the lack of 

uniformity of sprinkler spray density on the load platform. 

Figure 5 shows the average and standard deviation of 3 sprinkler 

spray density measurements. The sprinkler spray density data shown 

5 
was typical of sprinkler spray density tests taken during the 

duration of the test series. For the fuel package area on the load 

platform, an average spray density of 0.07 m/s (0.1 gpm/ft2) was 

measured consistently throughout this study. However random 

variations of local spray density within the area of the load 

platform were common. It should be noted that spray densities were 

measured in the absence of any fire, as is common practice. Fire 

induced gas flows are likely to modify the spray distribution 

during fire suppression. 

4. TEST PROCEDURE AND RESULTS 

The testing was performed under the main oxygen calorimetry hood at 

BFRL's large scale test facility. The fuel packages were weighed 

and positioned on an 2.44 m x 2.44 m (8 ft x 8 ft) load cell 

platform, which is located under the hood. Several of the fuel 

packages were burned with no water application to obtain HRR 

characteristics. Then sprinklered tests were conducted where the 

burning fuel was subjected to water spray. No attempt was made to 

simulate the response of a sprinkler to a similar fire in GSA 

office spaces. The time of sprinkler activation in these 

experiments was determined from observations during free burn tests 

and/or the amount of fire involvement during the period before 

sprinkler activation in the suppression tests. Sufficient pre-burn 

time was allowed such that each fuel package became well involved 

with fire and then the sprinkler was manually activated prior to 

reaching the fuel package's peak heat release rate. 

4.1 SOFA FUEL PACKAGE 

A vinyl covered, polyurethane foam cushioned sofa was chosen as the 

representative sofa fuel package. The burner was centered, front 

to back, on one end of the sofa (Figure 6). The outer side of the 

couch arm next to the burner was consumed within the first 200 

seconds. After the burner was removed (200 s), the fire propagated 

to the seat and back cushions. The accompanying rapid HRR increase 

can be seen on Figure 7. At approximately 7 minutes from ignition, 

one half of the sofa was involved in fire, the HRR was 450 kW. The 

fire intensity decreased significantly until flames worked their 

way to the bottom of the sofa. Then the rest of the sofa became 

involved and the HRR went up to its second peak of 600 kW at 835 s 

(approximately 14 minutes) . 21 minutes into the test the sofa 

collapsed and continued to burn. Data collection was stopped after 

35 minutes. 

The burn was then repeated with a similar sofa for the suppression 

measurements. The objective was to activate the sprinkler as close 

as pssible to the first HRR peak and/or when half of the surface 

area of the sofa was aflame. It was also important to activate the 

sprinkler during a period of fire growth to insure that the 

majority of the decrease in HRR was attributable to the sprinkler 

spray and not to a decrease in available fuel. 

6 
When the second sofa burn reached a peak HRR of 280 kW the 

sprinkler was activated. The water extinguished the visible flames 

on the upper surfaces of the sofa within a matter of seconds. Some 

small flamelets (less than 150 mm (6 in) in length) continued to 

burn on the underside of the couch, but the HRR was below the lower 

limit of the instrumented hood which is approximately 50 kW. 

4.2 CHAIR FUEL PACKAGE 

An upholstered leather chair with blended cotton felt and horse 

hair padding was used for the second item in the executive 

furnishings scenario. After the burner was removed, the flame 

would not sustain itself or propagate on the chair, Hence, the 

chair was not considered further in this study. 

4.3 OFFICE FUEL PACKAGE 

Descriptions of the items, which composed the office fuel package, 

and their respective weights are listed in Table 1. The burner was 

positioned under the reference table next to the 4 boxes of paper. 

The gas pipe leading to the burner can be seen under the table in 

the lower right hand corner of Figure 8. Examining the 

unsuppressed HRR curve in Figure 9, 4 HRR peaks are found. The 

first peak is representative of the reference desk and the 

materials under it. The second peak occurs when the side of the 

desk adjacent to the reference table is involved and the computer 

terminal is burning. The third and largest peak of 1.3 MW 

represents the added involvement of the office chair. The final 

peak occurs when the desk becomes involved, The package was 

allowed to burn for more than an hour before being extinguished. 

Looking at the two HRR curves for the suppression tests (Figure 9) 

it is apparent the HRR is substantially higher than the first peak 

on the unsuppressed HRR curve. The HRR peaked at 1.1 MW in the 

first sprinklered test and at 950 kW in the second sprinklered 

test. This was the result of the computer terminal igniting during 

the initial growth stage of these fires. When the sprinkler was 

activated the flames on the top surfaces of the desk and reference 

table were suppressed within a matter of seconds. However, the 

materials under the reference table as well as the underside of the 

reference table and the shielded side of the desk continued to 

burn. Small flamelets continued to be visible for approximately 30 

minutes in both of the suppression tests. 

4.4 WORK STATION I FUEL PACKAGE 

The work station components are listed in Table 2 and shown in 

Figure 10. The burner was positioned under the side work surface 

next to four boxes with paper on top of them just as in the office 

fuel package. Within two minutes after ignition the ABS bucket 

chair started to burn, resulting in the rapid increase in HRR as 

shown in Figure 11. Approximately one minute later flames had 

7 
spread to the computer terminal. The fire continued to grow until 

it reached its peak HRR of 1.7 MW at approximately 300 seconds. 

The fuel package maintained a HRR in excess of 500 kW for more than 

15 minutes. 

For the work station fire suppression tests, the sprinkler was 

activated at 4 minutes after ignition. The peak HRR in both of the 

cases was approximately 1.3 MW when the sprinkler was activated. In 

both cases the paper products on the top surfaces of the desk were 

extinguished quickly, but the computer terminal and the plastic chair continued to burn, though at a diminished rate. The 

difference in the HRR between the two suppression tests after the 

initial HRR reduction was due to the amount of burning material in 

shielded areas under the desk. 

4.5 TRASH CART FUEL PACKAGE 

The trash cart fuel package consisted of a 0.38 m3 (13.5 ft3) 

polyethylene utility tilt truck loaded with 45.5 kg (100 lbs) of 

paper trash. An electric match was inserted in the trash and the 

contents of the cart was ignited. The trash cart and it's contents 

burned very slowly. One side of the trash cart began to melt 90 

seconds after ignition. The opposite side began to melt 3 minutes 

after ignition. There were no visible flames above the top of the 

cart. The cart continued to burn, melt and collapse. The flames 

were small and close to the fuel surface. The cart burned for more 

than 30 minutes. The heat release rate for this package was not 

high enough to be measured accurately under the large instrumented 

hood. Since this type of fire would offer little if any fire 

suppression challenge to the sprinkler, this fuel package was not 

evaluated further, 

4.6 WORK STATION I1 FUEL PACKAGE 

Work Station I1 had the highest HRFt of the fuel packages tested 

during this study. The components of Work Station I1 are listed in 

Table 3, This work station was more enclosed than the Work Station 

I fuel package, due to the partial third side partition (Figure 

12). The flame spread up the surface of the partition, next to the 

burner, to ignite the papers on the desk top and eventually spread 

to the papers and notebooks on the shelf. The fire growth was 

modest (Figure 13) and appeared to be declining until the shelf 

collapsed at approximately 5 minutes after ignition. This dropped 

some of the burning paper into the chair seat and spread paper 

about the floor near the base of the partition. As the chair fire 

grew, the HRR rate was driven to the 1 MW range. Fire spread 

across the interior surfaces of the partitions until the entire 

work station was involved, reaching a peak HRR of 6.7 MW at 

approximately 9 minutes after ignition. 

The repeat of the fire for the sprinklered case grew in a similar 

fashion with the shelf collapsing at 225 seconds. The fire spread 

8 
to the chair at 325 seconds and the sprinkler was activated at 360 

seconds at a HRR of 700 kW. The majority of the fire was 

suppressed within 30 seconds of sprinkler activation. Burning 

continued in the shielded area under the desk for approximately 

another 10 minutes. 

4.7 PAPER RECYCLING CART FUEL PACKAGE 

The paper recycling cart was an 0.63 m3 (18 bushel) canvas hamper 

similar to those used by the post office. 

11.4 kg (25 lbs) of shredded paper in polyethylene bags. This fuel 

package was ignited with an Itelectric match" which was positioned 

half way up from the bottom of the cart between the bags. 

This package had a peak HRR of approximately 700 kW, at the time of 

sprinkler activation. The sprinkler was activated at 270 seconds 

after ignition. The majority of the visible flames were 

extinguished within 1 minute of sprinkler activation. Figure 14 

shows the HRR curve post sprinkler activation. 

It was filled with 

4.8 EXECUTIVE DESK FUEL PACKAGE 

The components for the executive desk fuel package are listed in 

Table 4. The significant difference between this package and the 

office fuel package is the use of two upholstered chairs; a high 

back executive style chair behind the desk and a pedestal base 

visitors chair next to the desk. Also no reference table and no 

%opier paper cardboard boxes" full of files were used in this 

scenario. The sprinkler was activated at a HRR of 545 kW, 900 

seconds after ignition. Since there was very little shielded fuel 

in this fuel package the HRR decreased rapidly following a trend 

similar to the paper recycling cart as shown in Figure 14. 

4.9 OFFICE I1 FUEL PACKAGE 

The Office I1 fuel package is similar to the Office I fuel package 

with the exception of using two computers instead of one, one on 

the reference table and one on the desk (Table 5). The sprinkler 

was activated at a HRR of 425 kW, 840 seconds after ignition. The 

shielded fuel in this scenario delayed the HRR reduction for almost 

two minutes before the sprinkler spray made a noticeable impact on 

the HRR (Figure 14) . 

4.10 SECRETARIAL DESK FUEL PACKAGE 

The secretarial desk fuel package components are listed in Table 6. 

In this case the chair was pushed under the desk. This allowed the 

fire to become well established underneath the desk as well as 

underneath the side extension where the Vopier paper cardboard 

boxes" were located. The sprinkler was activated at a HRR of 

550 kW, 240 seconds after ignition. The fires on the top of the 

desk (i.e. computer, files, etc) were suppressed within 2 minutes. 

However, the shielded fire under the horizontal work surfaces 

9 
continued to burn vigorously for approximately another 3 minutes 

before the HRR began decreasing (Figure 14). The fire did not 

spread from the shielded area to other portions of the fuel 

package, hence the fire can be considered to be controlled by the 

sprinkler. 

5. HEAT RELEASE RATE REDUCTION FACTOR FOR FURNISHINGS 

The purpose of this study was to develop an empirically based 

sprinkler fire suppression algorithm. The basis of the algorithm 

is the HRR curves described in the previous sections. Dividing the 

sprinklered HRR curve by the HRR at the time of sprinkler 

activation for each fuel package yields a dimensionless quantity 

which represents the decreasing HRR with respect to time during 

suppression. This was done for each fuel package. 

The normalized data are shown on a semi-log plot (Figure 15). 

Walton's wood crib data[2] (Figure 3) is also shown on Figure 15. 

It can be seen that a majority of the furnishing fire data is 

bounded by the data for the wood crib. The secretarial desk 

scenario, which exceeded the curve at times is an exception due to 

it's heavily shielded fire load and will be addressed in the 

Discussion section of this paper. Hence, using an exponential 

decay equation similar to the curve fit equation from the wood 

cribs and constraining the y intercept to 1 yields the curve shown 

in Figure 15. Constraining the curve to pass through 1 at tact 

allows the upper bound concept to be used any time after sprinkler 

activation, and it provides some factor of safety. This curve 

represents the expected upper bound for the reduction of HRR for 

office furnishing fires at a given time after sprinkler activation 

and is given by the equation: 

HRR Reduction Factor - 

where: t = Time after sprinkler 

activation (s) 

5.1 SPRINKLERED FIRE SUPPRESSION ALGORITHM 

The sprinkler fire suppression algorithm can be used in the 

following manner to estimate the reduction of HRR due to sprinkler 

intervention. 

1) Identify the fuel package of concern. Match its 

description and composition to a fuel package described herein 

10 
or in other references containing fuel package descriptions 

and their associated HRR curves i.e.![1,4,10]. Another option 

is to choose a lrt2 firet1 representative of your fuel package, 

2) Utilizing the HRR curve from Step 1 run a sprinkler 

activation program. Let the time of sprinkler activation 

equal tact* 

3) To find the HRR after sprinkler activation at a given time, 

t, let 

At t - tact 

Substituting At into HRR reduction factor equation will yield 

the HRR reduction factor at that time, Multiplying the HRR at 

sprinkler activation, Qact, by the HRR reduction factor gives 

the estimated upper bound to the HRR at that time after 

sprinkler activation. 

4) Step 3 can be repeated at several different times after 

sprinkler activation to develop a HRR reduction curve for the 

given fuel package during sprinklered fire suppression. 

A subroutine is being developed for the GSA Engineering Fire 

Assessment System [4] to perform this calculation, 

6. DISCUSSION 

The HRR reduction factor constitutes a Itzeroth orderv1 fire 

suppression model, As with most models, certain assumptions and 

limitations must be considered when applying this model, The tests 

upon which this model was based were all burned in the open i,e. no 

compartment effects. There are potential phenomena in a 

compartment which could effect the reduction of heat release rate 

of the fire. 

The water spray density is assumed to be at least 0.07 mm/s 

(0.1 gpm/ft2), A previous study[2] has shown the effect of 

reducing the water spray density. Such reduction can dramatically 

increase the time required to control a fire or if the density is 

too low, the ability to control the fire can be lost, 

The tests were conducted with a broad cross section of office 

furnishings. In Figure 15 the exponential HRR reduction curve is 

11 
shown to bound most of the experimental data, with the noticeable 

exception of the secretarial desk test. The measured HRR of the 

secretarial desk exceeded portions of the bounding HRR reduction 

curve. This was a scenario where shielded fuels were heavily 

involved with fire prior to and after sprinkler operation. Even 

though the HRR rate increased or remained high after sprinkler 

operation, the fire did not spread outside of the shielded area. 

Fuel load geometry is clearly one of the limitations of this and 

many other xiodels. Efforts were made to overcome this limitation 

by basing the HRR reduction factor on test data. However, if the 

HRR reduction curve were based solely on heavily shielded fires 

such as the secretarial desk it would be much too conservative for 

the majority of the other test cases. Further, activation of more 

than one sprinkler head would mitigate the adverse impact of 

shielding on fire suppression. 

This algorithm provides the user with a tool to predict sprinklered 

fire suppression for potential office fire situations. Fire 

suppression prediction could be improved and generalized by further 

research into the effect of compartments on suppression of fires 

and fuel packages for different classes of occupancy with different 

water spray density requirements. This model addresses the impact 

of the sprinkler on the HRR of the fire, additional research is 

needed to evaluate other effects such as sprinklered cooling of the 

fire gases and sprinklered cooling of compartment surfaces. 

7. CONCLUSIONS 

An empirically based sprinklered fire suppression methodology was 

developed from the measured HRRs of eight different fuel packages 

during fire suppression experiments. The reduction in HRR under 

suppression conditions was found to be bounded by an exponential 

function of time. 

HRR Reduction Factor - e-owo023t 

where: t - Time after sprinkler 

activation (s) 

Multiplying the HRR reduction factor by the HRR at the time of 

sprinkler activation, Qact, yields an expected upper bound to the 

HRR at a given time after sprinkler activation for office 

furnfshing fires that are not heavily shielded. 

Qact 

e -0.0023 t 

12 
Calculating this value at different times after sprinkler 

activation will provide a bounding HRR reduction curve for the 

office furnishings in question. The sprinkler effectiveness 

methodology can be thought of as a 9zeroth order" fire suppression 

model, for "light hazard" occupancies with a sprinkler spray 

density of 0.07 m/s (0.1 gpm/ft*) or greater. 

8. ACKNOWLEDGEMENTS 

Appreciation is extended to L. DeLauter, J. McElroy, R. McLane, 

G, Roadarmel and R. Zile of the Building and Fire Research 

Laboratory for their assistance in performing this study. 

Appreciation is also extended to D. Bathurst, D. Frable and D. 

Stroup of GSA for their support of this project. 

9. REFERENCES 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

Walton, W.D. and Budnick, E.K., Quick Response Sprinklers in 

Office Configurations: Fire Test Results. Nat. Bur. Stand. 

(U.S.) NBSIR 88-3695; January 1988. 

Walton, W.DOI Suppression of Wood Crib Fires with Sprinkler 

Sprays: Test Results. Nat. Bur. Stand. (U.S.) NBSIR 88-3696; 

January 1988. 

Walton, W.D., Nat. Inst. Stand. Tech. (U.S) , to be published. 

Nelson, H.E. , FPETOOL: Fire Protection Tools for Hazard 

Estimation. Nat. Inst. Stand. Tech. (U.S.) NISTIR 4380; 

October 1990, 

NFPA 13, Standard for the Installation of Sprinkler Systems, 

1991 Ed. National Fire Protection Association, Quincy, MA. 

Babrauskas, V., Will the Second Item Ignite? Fire Safety 

Journal, 4 (1981/1982), pp 281-292 

Babrauskas, V., Lawson, J.R., Walton, W.D., and 

Twilley, W.H., Upholstered Furniture Heat Release Rates 

Measured with a Furniture Calorimeter. Nat. Bur . Stand. (U. S. ) 

NBSIR 82-2604; December 1982. 

Parker, W.J., Calculation of the Heat Release Rate by Oxygen 

Consumption for Various Applications. Nat. Bur, Stand. (U.S.) 

NBSIR 81-2427-1; March 1982. 

Beyler, C.L., The Effects of Selected Variables on the 

Distribution of Water from Automatic Sprinklers, Volume 1: 

Analysis. Univ, of Maryland, Dept of Fire Prot. Engr.; 1977. 

13 
10. Gross, D., Data Sources for Parameters Used in Predictive 

Modeling of Fire Growth and Smoke Spread. Nat. Bur. Stand, 

(U.S.) NBSIR 85-3223; September 1985. 

14 
Table 1. Office Fuel Package Components 

15 
Table 2. Work Station I Fuel Package Components 

~ ~~ 

Item Description (cm) 

Wooden Desk with Metal Frame 

Side Extension for Desk 

152 X 610 X 76h 

91 X 46 X 46h 

WORK STATION I - 

Mass (kg) 

114.1 

' Computer Terminal with Keyboard 

Partition 152 x 2.5 X 165h 

Cloth Covered, Fiberglass Core, 

Metal Structure 

(2 at 23.6 kg each) 

(4 at 9.1 kg each) 

(9.1 kg on Boxes, 13.6 kg on 

Table) 

Box with Paper 46 X 29 X 24 

Computer Paper 

(I I ABS Bucket Chair, Padded with 

Metal Pedestal 

15.4 

47.3 

36.4 

22.7 

16.4 

Newspaper 

Publications 

0.9 

2.3 

I1 3 Phone Books I 2.3 

11 Paper for Notebooks & Files I 29.5 

I1 Notebooks & Files I 3.6 

I1 TOTAL I 290.9 

16 
Table 3. Work Station I1 Fuel Package Components 

WORK STATION I1 

Item Description (cm) 

Covered Particle Board Work 

Surface with Metal Supports 

183 X 610 X 76h 

ABS Bucket Chair, Padded with 

Steel Pedestal 

Computer Terminal with Keyboard 

Partitions: 

889 X 2.5 X 168h 

119 X 2.5 X 168h 

58 X 2.5 X 168h 

(2) 

(1) 

(1) 

Cloth Covered, Fiberglass Core, 

Metal Structure 

Box with Paper 46 X 29 X 24 

(4 at 9.1 kg each) 

Computer Paper 

(9.1 kg on Boxes, 13.6 kg on 

Table) 

3 Phone Books 

Newspaper 

Publications 

Paper for Notebooks & Files 

Notebooks & Files 

TOTAL 

Mass (kg) 

58.2 

15.9 

15.5 

103.6 

36.4 

22.7 

2.3 

0.9 

2.3 

29.5 

3.6 

290.9 

17 
Table 4. Executive Office Fuel Package Components 

Item Description (em) 

Wooden Desk 152 X 864 X 76h 

High Back Executive Chair 

Polyurethane Foam Padded with 

Metal Frame 

~~ 

II EXECUTIVE OFFICE 

Mass (kg) 

89.1 

18.6 

Upholstered Pedestal Chair, 

Neoprene Padding with Wooden 

Frame and Metal Pedestal 

Computer Terminal with Keyboard 

Computer Paper 

19.5 

15.5 

14.1 

Paper for Notebooks 6 Files 

TOTAL 

18 

9.1 

165.9 
Table 5- Office I1 Fuel Package Components 

OFFICE .I1 

Item Description (cm) 

Wooden Desk 152 X 864 X 76h 

Wooden Reference Table 

152 X 76 X 79h 

Padded Chair with Wooden Frame 

Computer Terminal with Keyboard 

(2) 

(4 at 9-1 kg each) 

(9.1 kg on Boxes, 13.6 kg on 

Table) 

Cardboard Paper Recycling Box 

30 X 30 X 69h,18 cm diameter hole 

in lid, Loose paper dropped in 

until 2/3 full 

Box with Paper 46 X 29 X 24 

Computer Paper 

Newspaper 

Publications 

Paper for Notebooks ti Files 

Notebooks & Files 

TOTAL 

Mass (kg) 

102 3 

42-3 

24.5 

26.8 

36.4 

22.7 

6.8 

Om9 

1.8 

29.5 

3.6 

297 6 

19 
SECRETARIAL DESK 

Item Description (cm) 

Wooden Desk with Metal Frame 

152 X 61 X 76h 

side Extension for Desk 

91 X 46 X 46h 

Wood framed chair with foam 

padded seat and back, secretarial 

Computer Terminal with Keyboard 

Partition 152 X 2.5 X 152h Cloth Covered, Fiberglass Core, 

Metal Structure 

type 

Box with Paper 46 X 29 X 24 

(4 at 9.1 kg each) 

Computer Paper 

(9.1 kg on Boxes, 13.6 kg on 

Table) 

3 Phone Books 

Newspaper 

Publications 

Paper for Notebooks & Files 

Notebooks & Files 

TOTAL 

Mass (kg) 

110.0 

14.1 

15.5 

21.4 

36.4 

22.7 

2.3 

0.9 

2.3 

29.5 

3.6 

258 6 

20 
lm 

Stick dimensions are approximately 3.8 cm x 3.8 cm x 61 cm. 

Figure 1. Wooden Crib Fuel Package 

21 
600 

500 

400 

1 

I I I I I I I I I I I I I 

SPRINKLER ACTIVATION 

- 

3 

-0 

300 - 

200 - 

100 - 

0 

0 300 600 900 1200 

NON-SPRINKLERED TIME (s) 

A 0.014 mm/s (0.021 GPM/FT2) 

11-.--.--.-1.-.1-. 0.039 mm/s (0.058 GPM/FT2) 

0 0.066 mm/s (0.097 GPM/FT2) 

--------- 0.081 mm/s (0.1 I9 GPM/FT2) 

x 0.084 mm/s (0.1 24 GPM/FT2) 

0.1 26 mm/s (0.1 86 GPM/FT2) -- -- -- 

Figure 2. Heat Release Rate Curves - Wooden Crib Fuel Package 

22 
1 

0.4 

0.3 

0.2 

0.1 

0 

b I 

l I I I 

I I I I 1 

200 400 600 800 

TIME (s) 

0, 73e(-~.~~225t) 

0.066 mm/s (0.097 GPM/fT2) 

0.081 mm/s (0.1 I9 GPM/n2) 

AVERAGE OF 0.066 mm/s AND 0.081 mm/s TESTS 

------- --- -- 

------------------. 

0 

Figure 3. Normalized Heat Release Rate Curves - Wooden Crib Fuel 

Package 

23 
x 

.- c 

Ei 

cf> 

B 7- I a 

Q 

0 

I 

1 

4 

a, 0 

u 

c, 

u1 

a 

E 

d 

td 

u 

-4 

a 

h 

E 

24 
w 

s" 

0 

+I 

3 

9 

0 

n 

v, 

s" 

3 

0 

+I 

0 

v 

h 

4 

s" 

0 

+I 

00 

b 

0 

9 

% 

W 

ti +I I +I +I 

% 

do gf 

+I +I 

-a 

v,b 

00 

+I +I 

n 

+I +I 

+I +I , 

\o 

s" 

0 

+I 

04 

O\ 

0 

9 

m 

\o 

0 

+I 

\o 

2 

0 

W 

0 

+I 

w 

00 

0 

9 

0 f 

+I 

M 

2 

.I 

W 

0 

25 
26 
700 

600 

500 

400 

300 

200 

100 

0 

n 

TIME (s) 

Figure 7. Heat Release Rate Curves - Sofa Fuel Package 

27 
28 
W 

- I

< 

W 

c/3 

< 

u 

I 

Lu 

CT: 

- I

< 

Lu 

a 

r 

1500 

1000 

500 I 

0 

TIME (s) 

NON-SPRI NKLERED 

SPRINKLERED 

---- SPRINKLERED (REPLICATE) 

Figure 9. 

------------------. 

Heat Release Rate Curves - Office Fuel Package 

29 
30 
TIME (s) 

NON-SPRI NKLERED 

SPRINKLERED 

---- SPRl NKLERED (REPLICATE) 

------------------. 

0 

Figure 11. Heat Release Rate Curves - Work Station I Fuel Package 

31 
Q) 

br 

rd 

x 

u 

rd 

PI 

PI 

Q) 

3 

E4 

H 

H 

Q) 

k 

3 

br 

-1 

Erc 

32 
8000 

LU 6000 

I- 

< 

cr 

w 

(0 4000 < 

W 

I 

w 

- I

< 

Lu 

a 

r 

2000 

0 

&! 

z 

TIME (s) 

Figu're 13. Heat Release Rate Curves - Work Station I1 Fuel Package 

33 
800 

600 

400 

200 

0 

TIME (s) 

SECRETARIAL DESK FUEL PACKAGE 

OFFICE II FUEL PACKAGE 

------------ EXECUTIVE DESK FUEL PACKAGE 

x PAPER CART FUEL PACKAGE 

l.-.-l-ll.l..------._I- 

# 

Figure 14. Heat Release Rate Reduction Curves - Paper Recycling 

Cart, Office 11, Executive Desk and Secretarial Desk 

Fuel Packages 

34 
1 

0.4 

Om3 

0.2 

Om I 

0 

+ 

- - - - -- 

e 

X 

I' I 

I 

200 400 600 

,(-0.0023) 

TIME (s) b 

PAPER CART FUEL PACKAGE .. SECRETARIAL DESK FUEL PACKAGE 

EXECUTIVE DESK FUEL PACKAGE 

OFFICE II FUEL PACKAGE 

OFFICE I FUEL PACKAGE 

SOFA FUEL PACKAGE 

WORK STATION I FUEL PACKAGE 

WORK STATION I1 FUEL PACKAGE 

WOOD CRIBS FUEL PACKAGE [2] 

800 

Figure 15. Envelope of Normalized Heat Release Rate Curves with 

HRR Reduction Curve 

35 
w, 

NIST-114A U.S. DEPARTMENT OF COMMERCE '* cuuIcATwlw OR RaORT NuMmm 

(REV. W) NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY , NISTIR 4833 

2. PERFORMINO OROAMlUnON REPORT NUMBER 

BIBLIOGRAPHIC DATA SHEET 

4. TmRAlloSlmmu 

6. PERFORMINO ORQAWlunON (IF JOINT OR OTHER 'T)uw MIST, SEE INSTRUCTIONS) 

US. DOlMTNPWT OC COMMERCE 

NATIONAL INSTIIVTE OF STANDARDS AND TECHNOLOOY 

cutmElrsuJRa,wo amw 

I 

A Sprinkler Fire Suppression Algorithm for the GSA Engineering Fire Assessment System I 

7. CONTMCT/oruWrWuulER 

8. TyppOFREPORTAwDPERw)DCOVERED 

A study was conducted to develop a sprinkler fire suppression algorithm for use with sprinklei 

activation time models. Large scale experiments were performed to determine the heat release 

rate (HRR) of selected office fuel packages with and without sprinklers operating. 

different fuel packages were evaluated. 

develop a time dependent HRR reduction factor. HRR Reduction Factor e where: t - 

Time after sprinkler activation (8) 

multiplying the HRR reduction factor by the HRR at the time of sprinkler activation, Qact, 

yielding an expected upper bound to the HRR at a given time after sprinkler act v 

This sprinkler fire suppression algorithm can be thought of as a "zeroth orser 

suppreesion2model for " light hazard" occupancies with a sprinkler spray density of 0.07 m/s 

(0.1 gpm/ft ) or greater. 

Eight 

The results from these experime_"6~ou~~~ used to 

The sprinkler fire suppression algorithm consists of 

Q(t), for office furnishing fires that are not heavily shielded. Q(t) - Qa te,I -8. d6BP 

fire 

12. KW WORDS (6 TO 12 mlE8; OROW; CIWTAUZE: ONLY MOPER "€8; AND SE?MATt Kov WORDS BY SEMICOLONS) 

crib fires; fire suppression; fire tests; fuel load; free burning fires; heat release rate; 

sprinklers 

13. AVAWA.WTV 

UWUYClrP) 

COR OmcuL DRTR#UTION. DO NOT RWIE TO MATK)cIAL TECHWlCAL mFORMATION SERVICE (NTIS). 

ELECTRONIC FOUM __