NISTIR 6510

Simulation of the Dynamics of the Fire at 3146 Cherry Road NE

Washington D.C., May 30, 1999

Daniel Madrzykowski

Robert L. Vettori
NISTIR 6510

Simulation of the Dynamics of the Fire at 3146 Cherry Road NE

Washington D.C., May 30, 1999

Daniel Madrzykowski

Robert L. Vettori

Building and Fire Research Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899-8644

April 2000

U.S. Department of Commerce

William M. Daley, Secretary

Technology Administration

Dr. Cheryl L. Shavers, Under Secretary of Commerce for Technology

National Institute of Standards and Technology

Raymond G. Kammer, Director
iii

TABLE OF CONTENTS

List of Tables.................................................................................................................................iv

List of Figures.................................................................................................................................v

1. ABSTRACT.......................................................................................................................1

2. INTRODUCTION...............................................................................................................2

3. FIRE INCIDENT SUMMARY...........................................................................................2

4. NIST FIRE DYNAMICS SIMULATOR (FDS).................................................................3

5. SMOKEVIEW....................................................................................................................3

6. FDS INPUT ........................................................................................................................3

6.1. Geometry................................................................................................................4

6.2. Vents.......................................................................................................................5

6.3. Material Properties.................................................................................................6

7. MODEL RESULTS ............................................................................................................7

7.1. Heat Release Rate of Fire.......................................................................................7

7.2. Fire Simulation 1 - Reported Fire Events - Temperature, Velocity, and Oxygen 

Concentration Predictions.......................................................................................7

7.3. Fire Simulation 2 - Opening of the Sliding Glass Door on the First Floor Prior to 

the Opening of the Sliding Glass Door in the Basement - Temperature and Velocity 

Predictions..............................................................................................................9

8. SUMMARY......................................................................................................................10

9. REFERENCES.................................................................................................................11
iv

LIST OF TABLES

Table 1. Approximate Timeline Based on Reconstruction Committee Input..................................4

Table 2. Time of Ventilation Events for FDS Simulation..............................................................5

Table 3. Thermal Properties Data [1,4].........................................................................................6

Table 4. Furniture Materials and Size ...........................................................................................6
v

LIST OF FIGURES

Figure 1. Plan view of first floor.................................................................................................12

Figure 2. Plan view of basement..................................................................................................13

Figure 3. Heat release rate from FDS Simulation........................................................................14

Figure 4. Perspective view of townhouse....................................................................................15

Figure 5. Grid layout in the xz plane............................................................................................16

Figure 6. Temperature slice along basement sliding glass door, at 200 s of simulation. .............17

Figure 7. Vector representation of velocity slice along basement sliding glass door, at

 200 s of simulation ..............................................................................................18

Figure 8. Temperature slice along front door, at 200 s of simulation. .........................................19

Figure 9. Vector representation of velocity slice along front door, at 200 s of simulation. .........20

Figure 10. Temperature slice along centerline of stairway, at 200 s of simulation......................21

Figure 11. Vector representation of velocity along centerline of stairway, at 200 s of

 simulation. ...........................................................................................................22

Figure 12. Percent oxygen along basement sliding glass door, at 200 s of simulation. ................23

Figure 13. Percent oxygen along centerline of stairway, at 200 s of simulation...........................24

Figure 14. Vector representation of velocity at the ceiling, at 200 s of simulation. .....................25

Figure 15. Vector representation of velocity at first floor window, 1.6 m off the

 floor, at 200 s of simulation.................................................................................26

Figure 16. Temperature slice along centerline of stairway with first floor sliding glass

 door vented, at 200 s of simulation......................................................................27

Figure 17. Vector representation of velocity at the ceiling with first floor sliding glass

 door vented, at 200 s of simulation......................................................................28
1

Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C.

May 30, 1999

Daniel Madrzykowski

Robert L. Vettori

1. ABSTRACT

This report describes the results of calculations using the NIST Fire Dynamics Simulator (FDS) that 

were performed to provide insight on the thermal conditions that may have occurred during the fire at 

3146 Cherry Road NE, Washington D.C. on May 30, 1999. Input to the computer model was 

developed from 3 sources; the District of Columbia Fire and Emergency Medical Services Department 

Reconstruction Committee, photographs and measurements taken by NIST staff during a June 3, 1999 

site visit, and from material properties taken from the FDS database.

An FDS model scenario was developed that best represented the actual building geometry, material 

thermal properties, and fire behavior based on information from the Reconstruction Committee and 

physical evidence. The results from this model scenario are provided with this report. Results from 

an additional model scenario, which included the opening of the sliding glass door on the first floor 

prior to opening of the sliding glass door in the basement, are also presented.

The FDS calculations that best represent the reported fire conditions indicate that the opening of the 

basement sliding glass doors provided outside air (oxygen) to a pre-heated, under ventilated fire 

compartment, which then developed into a post-flashover fire within 60 s. Some of the resulting fire 

gases flowed up the basement stairwell with high velocity and collected in a pre-heated, oxygen 

depleted first floor living room with limited ventilation. 

Key Words: cfd models; computer graphics; fire dynamics; fire fatalities; fire fighters; fire

investigations; fire models; fire simulations; ventilation
2

2. INTRODUCTION

Part of the mission of the Building and Fire Research Laboratory (BFRL) at the National Institute of 

Standards and Technology (NIST) is to conduct basic and applied fire research, including fire 

investigations, for the purposes of understanding fundamental fire behavior and to reduce losses from 

fire. 

On May 30, 1999 a fire in a townhouse at 3146 Cherry Road NE, Washington D.C. claimed the lives 

of two District of Columbia firefighters and burned other firefighters. The District of Columbia Fire 

and Emergency Medical Services Department Reconstruction Committee requested the assistance of 

NIST for the purpose of examining the fire dynamics of this incident. NIST has performed computer 

simulations of the fire using the newly developed, NIST Fire Dynamics Simulator (FDS) and 

Smokeview, a visualization tool, to provide insight on the fire development and thermal conditions 

that may have existed in the townhouse during the fire. This document describes the input and the 

results of the NIST FDS calculations.

3. FIRE INCIDENT SUMMARY

This account of the events relevant to the fire at 3146 Cherry Road NE is based on information 

provided to NIST by the Reconstruction Committee. Shortly after midnight, on May 30th, 1999, 

occupants at 3146 Cherry Road, NE awoke to a smoke alarm that had activated in the residence. The 

occupants went downstairs to the first floor, found hot smoky conditions, and exited the residence via 

the front door, leaving the front door open. At 00:17:00 hrs, the first 911 call was received. The first 

engine arrived on the fire scene in approximately 6 minutes. At approximately 00:24:00, firefighters 

began entering the first floor via the front door. Conditions on the first floor were described as “heavy 

smoke,” with thick black smoke coming from the doorway. Within two minutes, the front window on 

first floor was taken out by firefighters to provide ventilation. The window was removed from the 

inside, due to obstructions from security bars on the outside. Firefighters were also opening the 

second story windows on the front of the house. The occupants had left the second story windows on 

the backside of the house open.

Firefighters positioned by the sliding glass doors on the basement level reported that the basement was 

fully charged with smoke and that upon arrival a few flames appeared briefly. The sliding glass door 

was broken out in two stages. First, the right half was taken out at approximately 00:26:20. Then the 

left side was removed approximately 20 s later, due to obstructions from security bars. After the 

sliding glass door was broken out, firefighters entered the basement to conduct a search. They 

reported that there were a number of small fires on the floor of the basement, and that the fires began to 

increase in size after the sliding glass door was opened. The firefighters were ordered out of the 

basement as the fire rapidly increased in size. The firefighters reported that a tunnel or path was open 

in the smoke that enabled them to find their way out of the basement to the exterior, just prior to the 

basement becoming fully involved with fire. Within two minutes after entering the basement, flames 

from the basement extended up the backside of the townhouse. Seconds later there was a report that a 

firefighter was down. Firefighters that were working on the first floor reported that they felt an intense 

blast of heat prior to exiting the building. Two of the firefighters working on the first floor, one 

positioned near the open doorway to the basement stairs and the other located near the sofa on the back 
3

wall of the townhouse, died from injuries caused by the fire. A third firefighter, positioned between 

the two firefighters that died, survived the fire, but sustained substantial burn injuries. 

The post fire investigation determined that the fire started near an electrical fixture in the ceiling of the 

basement. The basement had severe fire damage throughout, indicating a well-mixed, post-flashover 

fire environment. The stairway from the basement to the first floor also showed signs of flame 

impingement on the ceiling and walls. The door at the top of the basement stairs was open during the 

fire and had been partially burned away. The basement stairway opened into the living room on the 

first floor. The living room had significant deposits of soot throughout, with limited thermal damage. 

Most of the paper on the gypsum board walls and ceiling remained intact and sofas in the room only 

showed signs of pyrolization or limited burning on the upper portions of the back cushions and top 

surfaces of the seat cushions. Areas in the living room away from the basement door opening had less 

thermal damage.

4. NIST FIRE DYNAMICS SIMULATOR (FDS)

NIST has developed a computational fluid dynamics (CFD) fire model using large eddy simulation 

(LES) techniques [1]. This model, called the NIST Fire Dynamics Simulator (FDS), has been 

demonstrated to predict the thermal conditions resulting from a compartment fire [2,3]. A CFD model 

requires that the room or building of interest be divided into small rectangular control volumes or 

computational cells. The CFD model computes the density, velocity, temperature, pressure and 

species concentration of the gas in each cell, based on the conservation laws of mass, momentum, and 

energy, to model the movement of fire gases. FDS utilizes material properties of the furnishings, 

walls, floors, and ceilings to simulate fire growth and spread. A complete description of the FDS 

model is given in reference [1]. 

In large scale fire tests reported in [2], FDS temperature predictions were found to be within 15 % of 

the measured temperatures and the FDS heat release rates were predicted to within 20 % of the 

measured values [2]. For relatively simple fire driven flows, such as buoyant plumes and flows 

through doorways, FDS predictions are within experimental uncertainties [3]. Therefore the results 

are presented as ranges to account for this uncertainty. 

5. SMOKEVIEW

Smokeview is a visualization program that was developed to display the results of a FDS model 

simulation. Smokeview produces animations or snapshots of FDS results [4]. 

6. FDS INPUT

FDS requires as inputs the geometry of the building compartments being modeled, the computational 

cell size, the location of the ignition source, the ignition source, thermal properties of walls and 

furnishings, and the size, location, and timing of vent openings to the outside which critically influence 

fire growth and spread. The timing of the vent openings, Table 2, used in the simulation is based on an 

approximate timeline of the fire fighting activities in Table 1.
4

Table 1. Approximate Timeline Based on Reconstruction Committee Input

Incident 

Time

Actions Simulation 

Time

(s)

00:17:00 First call reporting fire.

00:18:40 Second call – “fire in basement”

00:23:00 Engine 26 on scene – “heavy smoke showing”

00:24:00 Engine 26 and Engine 10 firefighters enter front door. Engine 

17 layout.

0

00:24:50 Battalion Chief 1 directs Truck 4 to rear. 50

00:26:00 First floor front window removed. 120

00:26:20 Basement sliding glass door half out. 140

00:26:30 Firefighters from Rescue Squad 1 and Truck 4 enter basement. 150

00:26:40 Basement sliding glass door completely out. 160

00:26:50 Engine 17 firefighters in the rear, “fire small in basement” 170

00:27:20 Firefighters from Rescue Squad 1 and Truck 4 exit basement. 

“basement almost fully involved”

200

00:28:00 Estimated time that firefighters from Engine 26 and Engine 10 

are burned on first floor

240

00:28:40 Engine 17 in rear, “fire extending to first floor” 280

00:29:00 (End of simulation time) 300

Note: Direct comparison of simulation conditions with the actual incident conditions begin at

approximately 100 s of simulation time. 

6.1. Geometry

The floor plans of the basement and first floor of the townhouse are shown in Figures 1 and 2. The 

two levels of the townhouse are modeled by a 10.0 m (32.8 ft) x 6.0 m (19.7 ft) x 5.1m (16.8 ft) tall 

rectangular volume. For the FDS simulation this volume was divided into 76,500 computational cells. 

 Each cell has dimensions 0.2 m (7.9 in) x 0.2 m (7.9 in) x 0.1 m (3.9 in). The placement and size of 

the interior walls, doorways, and windows were taken from the dimensioned floor plans drawn by 

personnel of the DC Fire and EMS Department. FDS adjusts the dimensions to the nearest 

computational cell. Therefore the cell size is the resolution limit of vents, openings, furnishings, or 

walls within the model. The cell size was selected to give the best approximation of the actual 

dimensions of the townhouse geometry.
5

6.2. Vents

The basement was vented to the outside by a sliding glass door 1.7 m (5.6 ft) x 2.0 m (6.6 ft) high. For 

the simulation, the door vent was divided into two parts. The right half of the sliding glass door was 

opened at 140 s into the simulation and the left half was opened at 160 s into the simulation. 

The basement was open to the first floor by a 0.8 m (2.6 ft) x 2.0 m (6.6 ft) high doorway at the top of 

the stairs. As in the fire incident, this door was fully open during the simulation. The front door to the 

first floor was also fully open during the fire and the simulation. The door was 0.9 m (3.0 ft) wide and 

2.0 m (6.6 ft) high. The front window on the first floor was 1.7 m (5.6 ft) wide and 0.9 m (3.0 ft) high 

with a 0.9 m (3.0 ft) sill height. This window was opened at 120 s into the simulation. The other 

opening to the outside from the first floor was a sliding glass door at the rear of the house. This sliding 

glass door was located directly above the basement sliding glass door. This door remained closed 

and intact during the entire simulation. 

The stairway opening from the first floor to the second floor was 0.9 m (3.0 ft) wide and 3.4 m 

(11.2 ft) deep. This vent remained open during the entire simulation due to the windows in the front 

and rear of the second floor being open. The exact position of the open rear windows on the second 

floor is not known; therefore the stairway opening was used to represent the assumed area of the open 

second floor windows. The details of the second floor were not modeled in this simulation.

At the time of the fire there was no wind, therefore for the simulation it was assumed that openings to 

the exterior were at ambient pressure.

Table 2. Time of Ventilation Events for FDS Simulation

Time of Event

Vent Initial 

Conditions 120 s 140 s 160 s

Front Door Open Open Open Open

Front Window Closed Open Open Open

First half of basement 

sliding glass door Closed Closed Open Open

Second half of basement 

sliding glass door Closed Closed Closed Open

Stairway door between 

basement & first floor Open Open Open Open

Stairway opening between

first and second floor Open Open Open Open
6

6.3. Material Properties

The ceiling of the basement was composed of wood fiber ceiling tiles attached to wood furring strips, 

which were attached to the bottom of open wood trusses. Given the multiple surfaces in the ceiling 

floor system, several different approximations were used for the ignition temperature (320 °C to 

390 °C) and the heat release rate per unit area (200 kW/m2 to 400 kW/m2). The assumptions used for 

the basement ceiling materials are shown in Table 3.

 

The walls of the townhouse were painted gypsum board, assumed 12 mm (0.5 in) thick. The subflooring was plywood and was covered with carpeting in the living room area of the house. The 

ceiling on the first floor was also painted gypsum board. Several large furniture items were included 

in the scenario; a bookcase, bar, desk and sofa in the basement as well as a door and sofa on the first 

floor. The model inputs utilized for each material type are given below in Table 3 and the size of the 

furnishings are given in Table 4.

Table 3. Thermal Properties Data [1,4]

Material Thickness

(m)

Ignition 

Temperature

(° C)

Heat

Release 

Rate

(kW/m2)

Thermal 

Conductivity

(W/m K)

Thermal 

Diffusivity

(m2/s)

Basement 

Ceiling 0.025 330 300 0.14 8.3E-8

Gypsum

Board 0.013 400 100 0.48 4.1E-7

Pine 0.013 390 200 0.14 8.3E-8

Upholstered

Cushion 0.10 370 700 0.20 1.2E-6

Table 4. Furniture Materials and Size

Item Material Size

Bookcase Pine 2 m wide, 0.3 m deep, 2.4 m high 

Bar Pine 2 m wide, 1 m deep, 1.2 m high

Desk Pine 1.5 m wide, 0.75 m deep, 0.75 m high

Sofa Upholstered cushion 2 m wide, 0.75 m deep, 0.9 m high

First floor door to 

basement Pine 0.85 m wide, 0.05 m thick, 2.05 m high
7

7. MODEL RESULTS

7.1. Heat Release Rate of Fire

For the FDS simulation, a small fire with a specified heat release rate was used to start the fire 

growth. In this case a 30 kW source, 0.2 m (8 in) square, located 0.1 m (4 in) below the basement 

ceiling, served as the FDS fire source. Starting the simulation with a flaming ignition enabled fire 

development to be modeled within a reasonable computational time. The actual fire may have taken 

several hours to develop to the flaming stage. As the simulated fire spreads from the ignition source, 

first along the ceiling and then to other items in the basement, it develops quickly, but depletes its 

supply of oxygen for combustion. This rapidly decreases the heat release rate or energy that is being 

produced by the fire. This produced a pre-heated oxygen depleted condition similar to that described 

by firefighters upon their arrival at the Cherry Road fire.

A time history of the fire’s heat release rate, as predicted by FDS, is shown in Figure 3. Annotations 

on the figure highlight the venting activities and the resulting impact on the development of the fire. As 

shown in the graph, venting the basement results in a heat release rate increase of more than 10,000 

kW or 10 MW within approximately one minute.

7.2. Fire Simulation 1 - Reported Fire Events - Temperature, Velocity, and 

Oxygen Concentration Predictions

Figure 4 shows a perspective view of the three-dimensional townhouse simulation. The basement 

level and first floor levels are shown with furnishings. Figure 5 provides a side view of the 

townhouse. The grid depicting the computational cell size is also shown. The simulation results in 

Figures 6 through 15 have had all of the walls and other obstructions removed to provide a clear view. 

 The horizontal clear area is the floor between the basement and the first floor level. The results are 

shown as a “slice” or a “plane” with a color bar that represents the corresponding numerical 

quantities. The results presented are taken at 200 s of the simulation. At that time, the heat release 

rate and the thermal conditions have reached a quasi-steady state condition. These figures provide a 

snapshot of the calculated fire environment conditions that the firefighters may have been exposed to at 

approximately 00:27:20.

Figures 6 and 7 show the plane of temperatures and velocities that align with the center of the first 

sliding glass panel that was taken out on the basement level. This plane is located 3.4 m (11.2 ft) into 

the townhouse from the front of Figures 6 and 7. The upper portions of the figures represent the 

kitchen area on the left and the living room area on the right. In Figure 6, temperatures in excess of 

820 °C (1500 °F) are shown throughout the basement, with the exception of the cool air entering the 

basement through the open sliding glass doorway at the right of the figure. Similar hot gas temperature 

conditions exist in the living room area. The maximum temperatures in the kitchen are in the 500 °C to 

660 °C (932 °F to 1220 °F) range. The velocity vector plot in Figure 7 provides gas flow direction as 

well as the approximate velocities. The dominant flows in this plane are the fresh air entering the 

open basement doorway at approximately 4 m/s (10 mph) and the hot gas flow exiting the upper 

portion of the doorway at approximately 7 m/s (16 mph).
8

Figures 8 and 9 show the plane of temperatures and velocities aligned with the center of the front door 

and the hallway, 1.4 m (4.6 ft) into the townhouse from the front of the figure. The upper portions of 

the figures represent the hallway and living room areas and the lower portions represent the open area 

in the basement on the left and an area in the storage room (cooler temperatures) on the right. 

Predicted temperatures in the open area of the basement are in excess of 820 °C (1500 °F), from the 

ceiling to the floor level in some areas. On the first floor, hot gases can be seen along the ceiling, 

cooling as the gases move from the back of the townhouse to the front. Outside air at approximately 20 

°C (68 °F) can be seen entering the front door from the left. The gas moving into the townhouse, along 

the floor, from the front door increases from 180 °C to 260 °C (350 °F to 500°F) by the time it reaches 

the back of the townhouse (right side of figure). 

The flow direction of the gases can be seen in Figure 9. On the first floor, outside air is entering the 

lower portion of the open front doorway in the range of 4 m/s to 5.6 m/s (10 mph to 12.5 mph). Hot 

gases are exiting the upper portion of the same doorway with maximum velocities in the range of 

5.6 m/s to 6.4 m/s (12.5 mph to 14 mph). Toward the rear of the townhouse on the first floor, hot gas 

flows from the basement doorway in excess of 8 m/s (18 mph).

Figures 10 and 11 show the plane of temperatures and velocities that align with the center of the 

basement stairway, 0.4 m (1.3 ft) into the townhouse from the front of the figure. The temperature plot 

shows hot gases in excess of 820 °C (1500 °F) filling the stairwell, flowing out into the living room, 

across the living room ceiling and down the back wall. The clear-notched area on the right side is the 

outline of the sofa. Between the doorway to the basement and the sofa, the temperatures approximately 

0.5 m (1.6 ft) above the floor, to floor level are in the range of 180 °C to 260 °C (350 °F to 500 °F). 

The areas near the floor where the temperatures were the highest, were near the doorway to the stairs 

and near the sofa on the back wall. These locations correspond to the areas where the two firefighter 

fatalities were believed to have occurred. 

Figure 11 shows the effect of the stairway on channeling the hot gases up to the first floor. The speed 

at which the fire gases flow up the stairway and across the ceiling of the first floor exceed 8 m/s (18 

mph). At these velocities, the travel time for the gases from the front of the basement (left side of 

figure) to the back of the first floor (right side of figure) is less than 2 s. Between the doorway to the 

basement and the sofa, the velocities from approximately 0.5 m (1.6 ft) above the floor to floor level 

are in the range of 0 m/s to 1.6 m/s (0 mph to 3.5 mph). The right side of the basement shown is the 

storage area under the stairs.

Figures 12 and 13 show oxygen concentrations. Even though the previous temperature plots have 

indicted temperatures that are consistent with flaming conditions, that cannot be assumed. In addition 

to fuel and heat, oxygen is needed for flaming combustion to be present. These figures provide some 

insight on the amount of oxygen that was available in different parts of the townhouse. The upper, hot 

gas layers in the basement and on the first floor in the living room area contained less than 6 % oxygen 

(all gas percents are on a volumetric basis). These are areas where the fire may not have had enough 

oxygen to produce visible flames.

Figure 12 shows the slice aligned with the center of the right side of the basement sliding glass door. 

Again the outside air can be seen entering the basement through the open doorway from the lower right 
9

side of the plot. A thin layer of 16 % to 19 % oxygen can be seen close to the floor on the first floor. 

This airflow is coming from the front door.

Figure 13 gives a view of the oxygen conditions along the centerline of the basement stairway. The 

hot gases that are flowing up from the basement are oxygen depleted, ranging from 14 % to 16 % 

oxygen at the base of the stairs and decreasing to 6 % to 11 % oxygen at the top of the stairs. The high 

velocity hot gas layer that flows across the living room ceiling and down the back wall of the 

townhouse (right side of figure) contains less than 6 % oxygen. Given the oxygen depleted conditions, 

little if any flaming combustion would be taking place in the living room area at this time. The right 

portion of the basement represents the storage area under the steps.

Figures 14 and 15 show the velocity flow patterns near the ceiling of the first floor and at

approximately 1.6 m (5.2 ft) above the floor, respectively. The velocities in front of the doorway to 

the basement are in the range of 8 m/s (18 mph). Figure 15 shows the circulation of gases from the 

doorway to the basement, across the back wall of the townhouse and then out the front window. 

Velocities flowing through the house in this U– shaped pattern range from 0.80 m/s to 4.8 m/s (2 mph 

to 11 mph) at this level. These velocities coupled with the high gas temperatures will increase the rate 

of convective heat transfer to people or objects in that area.

7.3. Fire Simulation 2 - Opening of the Sliding Glass Door on the First Floor 

Prior to the Opening of the Sliding Glass Door in the Basement -

Temperature and Velocity Predictions

At the request of the Reconstruction Committee, a second fire simulation was conducted. All of the 

input to the second simulation was the same as the first, with one exception; the sliding glass door in 

the living room on the first floor of the house was opened at 120 s into the simulation. In the basement, 

results of the second simulation were similar to the first. On the first floor the hot gases were not as 

confined as in simulation 1 resulting in cooler temperatures near the floor.

Figure 16 shows the plane of temperatures that align with the center of the basement stairway, 0.4 m 

(1.3 ft) into the townhouse from the front of the figure. The temperature plot shows hot gases in excess 

of 820 °C (1500 °F) filling the stairwell, flowing out into the living room, across the living room 

ceiling and down the back wall. The clear-notched area on the right side is the outline of a sofa. This 

hot gas ceiling jet is similar to the hot gas conditions shown in Figure 10. The significant difference is 

in the region close to the floor. Between the doorway to the basement and the sofa, the temperatures 

from approximately 0.6 m (2 ft) above the floor, to floor level are in the range of 20 °C to 100 °C (68 

°F to 212 °F). This is at least an 80 °C (176 °F) temperature reduction in this area with the open 

sliding glass doorway on the first floor.

Figure 17 shows the velocity field at the ceiling of the first floor. Comparing this to Figure 14 shows 

that the velocity range is similar, approximately 8.5 m/s (19 mph) vs. 8 m/s (18 mph). The flow 

pattern at the ceiling is wider for the second simulation because part of the flow stream is going out of 

the open sliding glass doorway.
10

8. SUMMARY

The NIST FDS computer simulation predicted fire conditions and events that correlate well with 

information from the Reconstruction Committee and the damage, or lack of damage, to portions of the 

townhouse. The model simulated a fire that started in a combustible ceiling assembly in the basement 

of the townhouse. The fire grew and spread across the ceiling and into other fuels in the basement 

until it exhausted the available oxygen supply in the basement. While the fire’s heat release rate was 

being constrained by the lack of oxygen, firefighters made entry on the first floor of the building. 

Venting of the windows on the front of the townhouse on the first and second floors had no noticeable 

immediate impact on the fire development. 

However, the venting of the sliding glass doors in the basement increased the heat release rate of the 

fire very rapidly. The FDS calculation indicates that the opening of the basement sliding glass doors 

provided outside air (oxygen) to a pre-heated, under-ventilated fire compartment, which then

developed into a post-flashover fire within 60 s. The fire filling the basement forced high temperature 

gases (approximately 820 °C (1500 °F)) up the basement stairwell at velocities in excess of 8 m/s (18 

mph). The high velocity gas stream flowed into a pre-heated, oxygen depleted first floor living room. 

The FDS predictions show the hot gas flow moving across the living room ceiling and banking down 

the back wall of the townhouse. Between the doorway to the basement and the sofa on the back wall 

of the townhouse, the temperatures from approximately 0.5 m (1.6 ft) above the floor, to floor level are 

in the range of 180 °C to 260 °C (350 °F to 500 °F). These thermal conditions developed within 

seconds of the rapid fire growth in the basement.

Even though the upper layer hot gases have predicted temperatures that are consistent with flaming 

conditions, that cannot be assumed. In addition to fuel and heat, oxygen is needed for flaming 

combustion to be present. The upper, hot gas layers in the basement and on the first floor in the living 

room area contained less than 6 % oxygen when the basement fire was fully developed and extending 

up the stairs. These are areas, particularly the living room, where the fire may not have had enough 

oxygen to produce visible flames.

A second NIST FDS simulation was performed. The only difference was the opening of the sliding 

glass door on the first floor at 120 s of the simulation or 20 s prior to opening the basement sliding 

glass door. The most significant difference in the predictions is in the region close to the living room 

floor. Between the doorway to the basement and the sofa, the temperatures from approximately 0.6 m 

(2 ft) above the floor, to floor level are in the range of 20 °C to 100 °C (68 °F to 212 °F). This is at 

least an 80 °C (176 °F) temperature reduction in this area with the open sliding glass doorway on the 

first floor as compared to the first simulation with the door closed.
11

9. REFERENCES

1. McGrattan, Kevin B., Baum, Howard R., Rehm, Ronald G., Hamins, Anthony, Forney, Glenn 

P., Fire Dynamics Simulator – Technical Reference Guide, National Institute of Standards and 

Technology, Gaithersburg, MD., NISTIR 6467, January 2000.

2. McGrattan, Kevin B., Hamins, Anthony, and Stroup, David, Sprinkler, Smoke & Heat Vent, 

Draft Curtain Interaction – Large Scale Experiments and Model Development, National 

Institute of Standards and Technology, Gaithersburg, MD., NISTIR 6196-1, September 1998.

3. McGrattan, Kevin B., Baum, Howard R., Rehm, Ronald G., Large Eddy Simulations of Smoke 

Movement, Fire Safety Journal, vol 30 (1998), p 161-178.

4. McGrattan, Kevin B., Forney, Glenn P., Fire Dynamics Simulator – User’s Manual, National 

Institute of Standards and Technology, Gaithersburg, MD., NISTIR 6469, January 2000. 
Living room

Stairs down

to basement

Sofa

Kitchen

Stairs up to

second floor

Front door

Window

1.7m wide

0.9m high

1.1m sill

Bath room Closet

Living room

Stairs down

to basement

Sofa

Kitchen

Stairs up to

second floor

Front door

Window

1.7m wide

0.9m high

1.1m sill

Closet

10.0m

6.0m

Sliding door

1.7m X 2.0 m high

Figure 1. Plan view of first floor.

12
Area of origin

Sofa

Bookcase

Desk

Bar

Closet

Storage

Stairs up to

first floor

Sliding door

1.7m X 2.0m high

10.0m

6.0m

Figure 2. Plan view of basement.

13
0

2000

4000

6000

8000

10000

12000

14000

0 50 100 150 200 250 300

Time (s)

Heat Release Rate (kW)

1st floor front

window open, 120 s

Basement sliding glass

door open (right side), 140 s

Basement sliding glass

door open (left side), 160 s

Figure 3. Heat release rate from FDS Simulation.

14
Figure 4. Perspective view of townhouse.

15
Figure 5. Grid layout in the xz plane.

16
Figure 6. Temperature slice along basement sliding glass door, at 200 seconds of simulation.

17
Figure 7. Vector representation of velocity slice along basement sliding glass door, at 200 seconds of simulation.

18
Figure 8. Temperature slice along front door, at 200 seconds of simulation.

19
Figure 9. Vector representation of velocity slice along front door, at 200 seconds of simulation.

20
Figure 10. Temperature slice along centerline of stairway, at 200 seconds of simulation.

21
Figure 11. Vector representation of velocity along centerline of stairway, at 200 seconds of simulation.

22
Figure 12. Percent oxygen along basement sliding glass door, at 200 seconds of simulation.

23
Figure 13. Percent oxygen along centerline of stairway, at 200 seconds of simulation.

24
Figure 14. Vector representation of velocity at the ceiling, at 200 seconds of simulation.

25
Figure 15. Vector representation of velocity at first floor window, 1.6 m off the floor, at 200 seconds of simulation.

26
Figure 16. Temperature slice along center line of stairway with first floor sliding glass door vented, at 200 seconds of 

simulation.

27
Figure 17. Vector representation of velocity at the ceiling with first floor sliding glass door vented, at 200 seconds of 

simulation. 

28