NIST Technical Note 1838
 

Simulation of an Attic Fire

in a Wood Frame Residential

Structure - Chicago, IL

Craig G. Weinschenk 

Kristopher J. Overholt 

Daniel Madrzykowski 

http://dx.doi.org/10.6028/NIST.TN.1838 

NIST Technical Note 1838

Simulation of an Attic Fire

in a Wood Frame Residential

Structure - Chicago, IL

Craig G. Weinschenk 

Kristopher J. Overholt 

Daniel Madrzykowski 

Fire Research Division 

Engineering Laboratory 

This publication is available free of charge from: 

http://dx.doi.org/10.6028/NIST.TN.1838 

August 2014 

UNITED STATES OF AMERICA

DEPARTMENT OF COMMERCE

U.S. Department of Commerce 

Penny Pritzker, Secretary 

National Institute of Standards and Technology 

Willie May, Under Secretary of Commerce for Standards and Technology and Acting Director 
Certain commercial entities, equipment, or materials may be identified in this 

document in order to describe an experimental procedure or concept adequately. 

Such identification is not intended to imply recommendation or endorsement by the 

National Institute of Standards and Technology, nor is it intended to imply that the 

entities, materials, or equipment are necessarily the best available for the purpose. 

National Institute of Standards and Technology Technical Note 1838

Natl. Inst. Stand. Technol. Tech. Note 1838, 39 pages (August 2014)

CODEN: NTNOEF
Contents

Contents iii
 

List of Figures iv
 

List of Tables v
 

List of Acronyms vi
 

List of Symbols vii
 

1 Introduction 1
 

2 Summary of the Fire Incident 2
 

3 Model Description 5
 

3.1 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
 

3.2 Fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
 

3.3 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
 

3.4 Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
 

3.5 Numerical Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
 

4 Model Results 16
 

4.1 Heat Release Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
 

4.2 Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
 

4.3 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
 

5 Discussion of Simulation Results 24
 

5.1 Simulated Hallway Flow Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
 

5.2 Assessing the Hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
 

5.3 Tactical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
 

6 Summary 32
 

References 34
 

A Dimensioned Drawings 38
 

iii
 
List of Figures
 

3.1	 Plan view of first (top) and second (bottom) floor of structure. . . . . . . . . . . . . 7
 

3.2	 Photographs showing the front (left) and rear (right) exterior of the structure after
 

the incident. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
 

3.3	 Post-incident image of rear porch door frame. . . . . . . . . . . . . . . . . . . . . . 12
 

3.4	 Front (left) and rear (right) of the structure with 10 cm computational mesh. . . . . 14
 

3.5	 Front-right side of the structure within the computational domain. . . . . . . . . . . 14
 

4.1	 HRR versus time from the FDS simulations. . . . . . . . . . . . . . . . . . . . . . 18
 

4.2	 Smokeview rendering of exterior combustion occurring on the rear side of the structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
 

4.3	 FDS simulated pressure contours, 1 s prior to interior door failure. . . . . . . . . . . 20
 

4.4	 FDS simulated velocity vectors, 15 s after interior door failure. . . . . . . . . . . . 21
 

4.5	 FDS simulated temperature contours, 1 s prior to rear door opening. . . . . . . . . . 22
 

4.6	 FDS simulated temperature contours, 1 s prior to interior door failure. . . . . . . . . 22
 

4.7	 FDS simulated temperature contours, 1 s after interior door failure. . . . . . . . . . 23
 

4.8	 FDS simulated temperature contours, 15 s after the interior door failure. . . . . . . . 23
 

5.1	 Post-fire image of interior door. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
 

5.2	 Post-experiment images of door failures. . . . . . . . . . . . . . . . . . . . . . . . 25
 

5.3	 Summary of simulated flow path on the second floor after interior door failure. . . . 26
 

5.4	 Temperature contours on the second floor, 1 s prior to interior door failure. . . . . . 28
 

5.5	 Temperature contours on the second floor, 5 s after interior door failure. . . . . . . . 28
 

5.6	 Temperature contours on the second floor, 60 s after interior door failure. . . . . . . 29
 

A.1 Dimensioned drawing of first floor. . . . . . . . . . . . . . . . . . . . . . . . . . . 38
 

A.2 Dimensioned drawing of second floor. . . . . . . . . . . . . . . . . . . . . . . . . . 39
 

iv
 
List of Tables

2.1 Abridged NIOSH approximate fire event timeline . . . . . . . . . . . . . . . . . . . 4
 

3.1 Timeline of ventilation changes in the simulation . . . . . . . . . . . . . . . . . . . 12
 

3.2 Relevant fire model input parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 15
 

4.1 Fire incident and simulation event timeline . . . . . . . . . . . . . . . . . . . . . . 17
 

5.1 Flow path related LODD/LODI incidents . . . . . . . . . . . . . . . . . . . . . . . 31
 

v
 
List of Acronyms
 

BC Battalion Chief 

E Engine 

FDS Fire Dynamics Simulator 

HGL Hot Gas Layer 

HRR Heat Release Rate 

HRRPUA Heat Release Rate per Unit Area 

IC Incident Command 

LODD Line of Duty Death 

NIOSH National Institute for Occupational Safety and Health 

NIST National Institute of Standards and Technology 

SFPE Society of Fire Protection Engineers 

SQ Squad 

TL Tower Ladder 

vi
 
List of Symbols
 

ft foot 

m meter 

min minute 

Pa Pascal 

psi pound per square inch 

s second 

W Watt 

k thermal conductivity 

ρ density 

cp specific heat 

vii 
Abstract
 

The Fire Dynamics Simulator (FDS) fire model, which is developed and maintained by the National 

Institute of Standards and Technology (NIST), was used to provide insight into the dynamics of a 

fire that occurred on November 2, 2012, within a 2 1⁄2 story, single family structure in Chicago, IL, 

that resulted in the death of the captain of a fire department. The inputs for the FDS simulations 

are documented in this report and are based on the fire scenario, including the building geometry, interior furnishings, and ventilation conditions. The fire started in the attic and spread down 

through an opening into the enclosed porch on the rear of the structure. This resulted in ventilation 

limited (fuel rich) fire conditions in the attic and rear porch areas. The spread of fire and hot gases 

into the second floor of the structure was limited by a closed steel-faced, wood-framed door. After 

exposure to the elevated temperatures and pressure from the fire in the porch area, the wood frame 

of the door decomposed, the steel faces of the door failed, and the door collapsed inward. The door 

failure resulted in the establishment of a flow path between the higher pressure and higher temperature conditions in the enclosed porch and the lower pressure and lower temperature conditions in 

the hallway and kitchen areas of the second floor. The temperature of the gases that flowed into 

the hallway exceeded 260 ◦C (500 ◦F) at a height of 1.86 m (6 ft). Unfortunately, a captain and 

firefighter were advancing a hose line in the hallway near the door at the time of the door failure. It 

appears that the captain was likely overcome by the rapid change in conditions before he could exit 

to the safety of the kitchen area. After a Mayday call, the captain was rescued from the structure, 

but later succumbed to his injuries. 
Section 1

Introduction

Part of the function of the Fire Research Division at NIST is to develop and apply technology, 

measurements, and standards to improve the understanding of the behavior, prevention, and control 

of fires to enhance fire fighting operations and equipment, fire suppression, fire investigations, and 

disaster response. NIST has previously used the Fire Dynamics Simulator (FDS) fire model to 

provide insight into the fire development and thermal conditions of fires that have resulted in line 

of duty deaths (LODDs) [1–5]. The objective of these studies has been to improve the safety and 

effectiveness of firefighters. 

On November 2, 2012, a fire in a 2 1⁄2 story wood frame residential structure claimed the life 

of a captain of the Chicago Fire Department. NIST examined the fire dynamics of this incident at 

the request of NIOSH and the Chicago Fire Department. Computer simulations of the fire incident 

were conducted using the NIST Fire Dynamics Simulator [6] and Smokeview [7] software to provide insight into the fire development and thermal conditions that likely existed in the residence 

during the fire. The specific objectives of the simulations detailed in this report are: 

1. To examine the effect of the flow path (including temperature, pressure, and fire conditions) in 

this multi-story residential structure using physics-based calculations. 

2. To provide visualizations of the fire behavior that are representative of the conditions that 

members of the Chicago Fire Department likely experienced during the course of their interior 

operations. 

This document describes the input and the results of the FDS (version 6.1.1) simulations. The 

simulations were developed using a combination of knowledge of the fire scenario and appropriate engineering approximations and assumptions. Analysis of the simulation results focuses on 

the hazardous conditions that developed following the development of a flow path inside of the 

structure. This document is organized as follows: Section 2 provides a summary of the fire incident, Section 3 describes the relevant model input parameters and assumptions that were used 

to develop the simulations, Section 4 presents the simulation results, and Section 5 discusses the 

simulation results as they relate to firefighter safety and effectiveness. Appendix A contains dimensioned drawings of the first and second floor of the structure. 

1
 
Section 2

Summary of the Fire Incident

The account of events for this incident was documented by the National Institute for Occupational 

Safety and Health (NIOSH) Fire Fighter Fatality Investigation and Prevention Program Report 

#F2012-28 [8]. For the purpose of this analysis, the details regarding the timeline are considered 

to be approximate values. The following narrative of the incident was extracted from the NIOSH 

incident report [8]: 

On November 2, 2012, a 54-year-old male career captain sustained injuries at a 2-1/2 story 

apartment building fire then died at the hospital. At 1716 hours, dispatch called a “Still” 

alarm1 for smoke in the area. Battalion Chief (BC) 19 was the first to leave the station that 

was just blocks away. He approached the fire structure by driving behind it then around to 

the front arriving on scene at 1717 hours. He reported a working fire with heavy smoke 

coming from the rear and front of the structure’s attic. Per fire department standard operating procedures, dispatch initiated a RIT response2. At 1718 hours, E123 arrived on scene 

and BC19 was on scene and had assumed incident command (IC). The IC spoke with one 

of the occupants who stated everyone was out. The IC made entry through the front door to 

the stairwell to survey the interior of the 2nd floor. He noticed only a light haze throughout 

and glow around the [rear] door to the covered porch. The IC came back to the front door 

and met the E123 captain and a firefighter. They had stretched a [hose] load which is 100 

feet of 21⁄2-inch, a gated wye, and 150 feet of 13⁄4-inch hoseline to go to the 2nd floor, which 

is a standard department hose lay for this type occupancy. At 1720 hours, E49, T33, and 

TL39 arrived on scene. 

The IC made entry to the 1st floor apartment and worked his way to [the rear of the structure]. He opened the [interior door opening into the rear foyer on the back side of the 

house] and noticed heavy fire in the covered porch and rear stairwell area. At 1721 hours, 

the [E123 captain] and firefighter were on the 2nd floor where they flaked out, charged, and 

began advancing the hoseline to the rear door of the apartment. The E49 crew had stretched 

a 21⁄2-inch hoseline [to the rear of the structure]. The T33 crew set a ground ladder on [the 

left side of the structure] and TL39 set the aerial to the roof about a third of the way back 

on [the left side]. A TL39 firefighter went to [the rear of the structure] to check doors. He 

1The department defines a “Still” alarm to be two engine companies, two truck companies, and a battalion chief. 

2The department defines a rapid intervention team (RIT) response to be one truck company, one battalion chief, 

one advanced life support (ALS) ambulance, and one emergency medical services (EMS) field officer. 

2
 
first went to the basement door which he was unable to force open. Then, he went to the 

first floor exterior enclosed porch door which was unlocked and he opened it up. He stated 

that he noticed fire light-up in the stairwell. He kicked in the locked door [that connects the 

1st floor rear porch to the rear foyer], [proceeded] to walk in, saw no fire then backed out. 

At 1723 hours, the IC radioed the [E123 captain] that there was heavy fire in the covered 

porch and attic area and that E49 was going to put water on the fire, around the [rear] attic 

window, but there was no acknowledgment from the [captain]. E49 proceeded to put water 

on the [rear of the structure]. The IC returned out front to the command post and donned his 

turnout gear. The lieutenant from TL39, the lieutenant and 2 firefighters from SQ5, and a 

E123 firefighter/paramedic (FF/PM) were near the kitchen area on the 2nd floor when they 

heard a loud commotion. The FF/PM heard the [E123 captain] yell “get out of here.” The 

FF/PM had no radio and he couldn’t locate the [captain’s] radio so he yelled Mayday as he 

tried to get the [captain] and other crew member untangled. The TL39 Lieutenant and SQ5 

fire fighters heard the FF/PM’s verbal Mayday and the SQ5 Lieutenant tried to transmit a 

Mayday over heavy radio traffic. 

At 1727 hours, the TL39 crew had just completed the first hole in the roof about midway 

on [the right side] roof with minimal fire showing, when they heard the Mayday. The IC 

verified that a firefighter was down, called a Mayday, and requested a 2-11 Assignment3 . 

Dispatch initiated a 2-11 alarm. SQ5 and other members on the 2nd floor grabbed the [E123 

captain] and got him down the stairs. The TL39 crew, with assistance from a T33 and SQ5 

firefighter, had just completed a second hole on [the right side] of the roof about a third 

of the way back when conditions worsened. At 1729 hours, the roof ventilation crew was 

back in the aerial basket when they noticed the [captain] being brought out to the front yard. 

The [captain] was nonresponsive in the front yard and CPR was successfully performed. 

The IC met the A19 crew and escorted them to the [E123 captain]. The revived [captain] 

was responsive and talking to the paramedics as he was loaded into the ambulance. At 1738 

hours, the [captain] was transported to the local hospital where he had complications during 

airway management and died. 

Table 2.1 shows an overview of the timeline of events. A plan view of the structure and the location 

where the captain collapsed are shown in Fig. 3.1, and more details of the fire development are 

provided in the following sections. 

3The department defines a 2-11 alarm as a second alarm upgrade. The response is four engines, two trucks, one 

tower ladder, two battalion chiefs, one deputy district chief, one air mask service bottle truck, and a media affairs unit. 

3
 
Table 2.1: Abridged NIOSH approximate fire event timeline [8]
 

Incident Time Fire Behavior / Fireground Operation 

[hh:mm:ss] 

17:16:00 Dispatch for a “Still” alarm - two engine companies, two 

truck companies, and a battalion chief. 

17:17:00 On-scene report of a working fire with heavy smoke coming 

from the front and rear of the structure’s attic. 

17:20:00 Attic windows break - heavy smoke out of front attic window and heavy smoke and fire out of rear. 

17:21:00 E123 captain and firefighter on second floor with 13⁄4-inch hoseline. 

17:21:30 First floor exterior porch door opened. 

17:23:00 Heavy fire report in rear stairwell and enclosed porch. No 

response from E123 captain or firefighter. 

17:24:00 Water applied to attic from the rear exterior position. 

17:25:00 SQ5 makes entry through front of structure. 

17:27:00 After hearing a Mayday call from SQ5, IC calls a Mayday. 

17:29:00 E123 captain carried out of structure. 

4
 
Section 3

Model Description

Fire Dynamics Simulator [6] is a computational fluid dynamics (CFD) model that solves a form 

of the Navier-Stokes equations appropriate for low-speed, thermally driven flow with an emphasis 

on smoke and heat transport from fires. Within a CFD model, the room or building is divided 

into small three-dimensional rectangular control volumes or computational cells. The cells are 

contained together within one larger volume known as a computational domain. The CFD model 

computes the density, velocity, temperature, pressure, and species concentration of the gas in each 

cell. Based on the laws of conservation of mass, momentum, and energy, the model tracks the 

generation and movement of fire gases. One of the most important advantages of FDS is that it 

is mathematically verified [9] and validated against fire test data to ensure that it provides the 

expected results, given sufficient input data [10]. A complete description of the FDS model is 

provided in the FDS Technical Reference Guide [11]. 

Smokeview is a software tool designed to visualize simulation results from FDS [7]. Smokeview visualizes smoke and other attributes of the fire simulation using traditional scientific methods such as displaying tracer particle flow, two dimensional (2D) or three dimensional (3D) shaded 

contours of gas flow data such as temperature and flow vectors showing flow direction and magnitude. Smokeview allows the fire and fire movement to be visualized. This is done by displaying 

a series of partially transparent planes where the transparencies in each plane (at each grid node) 

are determined from soot densities computed by FDS. Smokeview also visualizes static data at 

particular times using 2D or 3D contours of data such as temperature and flow vectors showing 

flow direction and magnitude. 

Input data from various sources must be collected and documented to simulate a fire using 

FDS or any other fire model. For the simulation results presented in this document, information 

was obtained from two primary sources. The following information was gathered from the fire 

scene: the geometry of the building and the compartments being modeled, the size and location 

of exterior and interior ventilation openings, and documentation of fire damage to the building. 

The following information was gathered from witnesses, first responders, reports, and recorded 

media such as fire ground radios or videos: information on the timing of the fire development, the 

sequence and approximate timing of ventilation openings to the outside, and weather conditions at 

the time of the fire. 

The analysis of the simulation results is focused on the interior conditions on the second floor 

before and after the interior door failure. Based on the goals of the analysis and the information 

collected, several engineering approximations were made. For example, the fire exhibited signs 

5
 
of under-ventilated conditions when firefighters arrived [8]; however, the exact ignition time, fire 

growth rate, and heat release rate (HRR) of the fire were not known. The ignition time and growth 

rate were estimated to reduce the amount of required calculation time while adhering to documented observations. The HRR of the fire was estimated using documentation of the potential fuel 

load within the structure. 

In reality, the quantities associated with these input parameters are not fixed values; rather, a 

model input parameter can be thought of as a point estimate from a distribution of possible input parameters with some associated amount of uncertainty. Any change in an input parameter 

(such as the HRR) for a given scenario would result in a change in the output quantity (such as 

the hot gas layer (HGL) temperature). For example, according to the McCaffrey, Quintiere, and 

Harkleroad [12] empirical correlation, the HGL temperature in a well-ventilated compartment fire 

is proportional to the HRR raised to the two-thirds power. Following this relationship, a 7.5 % 

increase in the HRR would result in a 5 % increase in the HGL temperature [13]. More detailed 

discussion on the propagation of parameter uncertainty in fire models is available in a validation 

study that was sponsored by the U.S. Nuclear Regulatory Commission [13]. The following subsections describe the inputs that were used to develop the simulation, including any approximations 

or assumptions that were made. 

3.1 Geometry

The structure involved in this fire incident was a 2 1⁄2 story residential building with balloon frame 

construction and a gable roof.1 The structure had a 17.15 m (56 ft) by 6.15 m (20 ft) footprint, 

as shown in Fig. 3.1. This results in a floor area of approximately 105 m2 (1100 ft2) per floor 

and a main living area of approximately 110 m2 (2200 ft2). The interior walls were constructed 

from nominal lumber covered by 12.7 mm (0.5 in) gypsum board [8]. Additionally, there was a 

half-story attic that contained the structure’s hot water heater. Three sets of stairs were present in 

the structure: one front stairwell that connected the first and second levels (Stair 1 in Fig. 3.1), one 

rear stairwell that connected the first and second levels (Stair 2 in Fig. 3.1) and a second rear set of 

stairs which provided access to the attic (Stair 3 in Fig. 3.1). Entry to the first floor of the structure 

can be made either in the front or rear, as shown in Fig. 3.1. 

The fire, which is described in Section 3.2, started in the attic and spread to the rear porch. 

Discussion of the fire’s impact on the interior conditions is provided in Section 4. Figure 3.2 shows 

the exterior of the front and rear of the structure after the incident. Note that the majority of the 

damage occurred in the attic and rear porch on the second floor. Fully dimensioned drawings of 

the interior of the first and second floors are shown in Figs. A.1 and A.2, respectively. 

1Balloon frame construction is a method of framing where a continuous stud runs from the bottom horizontal 

member to the top plate. Intermediate floors are built directly off of the studs. One potential issue with balloon frame 

construction is that without fire stops there is void space for fire to potentially travel between the floors within the wall 

cavity. 

6
 
1

1

2

2

A 

B 

Front Room

Stair 1

17.15 m

6.15 m

Stair 2

F

R

O

N

T

R

E

A

R

Rear

Foyer

1

1

2

2

A 

B 

Stair 1

6.15 m

17.15 m

Stair 3

Hallway

Kitchen

Stair 2

Rear

Porch

R

E

A

R

F

R

O

N

T

Location of

collapsed captain

Front Room

Figure 3.1: Plan view of first (top) and second (bottom) floor of structure. Stairs and key rooms are 

identified using measurements collected by NIST. 

7
 
Figure 3.2: Photographs showing the front (left) and rear (right) exterior of the structure after the 

incident. 

8
 
3.2 Fire
 

To estimate the type of fuel, fire size, and structure ventilation, on-scene videos and post-incident 

reports were used. Based on these sources of information, the FDS model includes two source 

fire locations: an initial fire in the attic and a secondary fire on the second floor porch landing. 

The attic and rear porch primarily consisted of wood fuel: the rear porch was enclosed with wood 

planks covered with foam board and vinyl siding, the roof consisted of asphalt shingles over wood 

planking, and the attic and porch floors were composed of oriented strand board. 

Wood fuel can be represented by the chemical formula, CH1.7O0.74N0.002, with specified yields 

of carbon monoxide (yCO = 0.004 kg/kg) and soot (yC = 0.015 kg/kg) [14]. The product yields 

are expressed in terms of the amount of carbon monoxide or soot emitted per unit mass of fuel 

consumed (kg/kg) and can be found in the Society of Fire Protection Engineers (SFPE) Handbook [14]. A balanced chemical reaction for wood combustion can be written as: 

CH1.7O0.74N0.002 +4.91(0.208 O2 +0.783 N2 +0.387E-3 CO2 +0.834E-2 H2O)

→ 5.74(0.636E-3 CO +0.168 CO2 +0.155 H2O +0.670 N2 +0.613E-2 C) (3.1) 

The value for the heat of combustion of wood used in this simulation was 16,400 kJ/kg, based 

on data provided in the SFPE Handbook [14]. The heat of combustion quantifies the amount of 

energy per unit mass of the fuel. The following text defines Eq. 3.1 for an FDS input file with the 

desired fuel and reaction properties discussed above: 

&SPEC ID='WOOD', FORMULA='CH1.7O0.74N0.002' / 

&REAC ID = 'wood' 

FUEL = 'WOOD', 

HEAT_OF_COMBUSTION = 16400, 

SOOT_YIELD = 0.015, 

CO_YIELD = 0.004/ 

Note that using the input lines above will invoke the simple chemistry reaction mechanism in 

FDS in which fuel and air react to form only CO2, CO, H2O, soot, and N2. If the inclusion for 

other combustion products is desired, then the user must explicitly define those species and the 

chemical reaction that produces them [6]. Based on the above input lines, FDS uses the default, 

mixing-controlled fast chemistry combustion model. This mechanism states that the rate of fuel 

consumption is proportional to both the local limiting reactant concentration and the local rate 

of mixing and extinction is based on the critical flame temperature approach [11]. While FDS 

provides users with the option to use a more complex finite-rate combustion mechanism, there is 

not sufficient evidence in this case to justify deviating from the default specifications. 

To estimate the heat release rate per unit area (HRRPUA) of wood, Babrauskas and Grayson [15] 

conducted experiments in a cone calorimeter2 to determine the 5-min average of the HRRPUA for 

several different types of wood over a range of radiant heat fluxes. The results of that study indicate 

that the HRRPUA for different types of wood is approximately 50 kW/m2 . 

2The cone calorimeter is an experimental apparatus used to gather data about ignition time, mass loss, combustion 

products, and heat release rate among other properties associated with burning small samples of materials [16]. 

9
 
To calculate the total fire size, the appropriate burning area (exposed wood area) of the attic 

and second floor porch enclosure needs to be determined. Based on the floor plan of the structure, 

the underside of the roof was approximately 134 m2 (1453 ft2) with 7 m2 (75 ft2) walls on the front 

and rear sides. Additionally, there was 105 m2 (1130 ft2) of floor area in the attic. Examination of 

post-incident images indicated that the floor immediately over the rear porch burned away. That 

area was considered to be part of the porch fire. Based on post-incident damage, approximately 

50 % of the remaining floor area and 90 % of the roof was considered to be fuel for the attic fire. 

To estimate the total attic fire size, the underside roof area (120 m2), two end walls (14 m2), and the 

floor area (43 m2 or 463 ft2) were included. Applying an HRRPUA of wood of 50 kW/m2 results 

in a potential peak fire size of 9 MW. To estimate the size of the porch fire, the four walls of the 

porch enclosure (42 m2 or 452 ft2) and the floor and ceiling of the porch (24 m2 or 258 ft2) were 

included, which results in a total porch area of 66 m2 (689 ft2). Using the same HRRPUA of wood 

of 50 kW/m2, the potential peak fire size on the porch was approximately 3.3 MW. Therefore, the 

maximum fire size for this structure was estimated to be 12.3 MW. Since the time at which the 

fire started is not known relative to the notification of a fire or how fast the fire spread, several 

simplifications were made. The first assumption is that the attic fire was specified to start at the 

beginning of the simulation and increase to a value of 9 MW in 10 s. The porch fire was specified 

to start 40 s into the simulation and increase to a value of 3.3 MW in 10 s. The 10-s ramp up 

time was used to prevent abrupt changes in the velocity at the fire boundary condition in FDS. 

The second assumption is that the sources of the gas phase wood fuel have constant areas at fixed 

locations (2 sources for the attic, 1 source for the porch). The following lines define the source fires 

in the FDS input file: 

&SURF ID='FIRE', HRRPUA=2250., COLOR='ORANGE', TAU_Q=10 /
 

&VENT XB=-13.5,-13,1,5,6.16,6.16, SURF_ID='FIRE' /
 

&VENT XB=-14.5,-14,1,5,6.16,6.16, SURF_ID='FIRE' /
 

&VENT XB=-16.5,-15.5,1,2.5,3.14,3.14, SURF_ID='FIRE', DEVC_ID='SECOND FIRE'/
 

&DEVC XYZ = -17.2,2,0, ID='SECOND FIRE', QUANTITY='TIME', SETPOINT=40,
 

INITIAL_STATE=.FALSE. / 

Note that the coordinates here are unique for the vents are specific to the input files used for these 

simulations. The key point is that they are 2-D planes located at a specific area. 

10
 
3.3 Materials
 

While the fires were represented as fuel sources with a constant area (Section 3.2), from a heat 

transfer perspective, it is important to define the material properties (density, thermal conductivity, 

and specific heat) to account for heat transfer and energy storage in the ceiling, walls, and floor. 

In this study, the material properties of gypsum board [17] were specified on the finished walls 

and ceilings on the main two floors of the structure, and the material properties of wood [18] were 

specified on the unfinished portions of the attic and rear porch. The following lines define these 

materials in the FDS input file: 

&MATL ID = 'GYPSUM BOARD' 

FYI = 'Wakili - Journal of Fire Sciences 2007' 

CONDUCTIVITY = 0.28 

SPECIFIC_HEAT = 1.0 

DENSITY = 810. / 

&MATL ID = 'WOOD MAT' 

FYI = 'Incropera and DeWitt, Fundamentals of Heat and Mass Transfer' 

CONDUCTIVITY = 0.12 

SPECIFIC_HEAT = 1.38 

DENSITY = 510. / 

3.4 Ventilation

The simulations in this study account for changes in the ventilation due to a combination of fire department operations (opening doors) and fire acting on the structure (fire breaching walls, breaking 

windows, etc). Two different ventilation scenarios were considered in this study. The first scenario 

involves a baseline simulation in which the ventilation times and ventilation areas represent our 

best understanding of the incident. The second scenario, or alternative simulation, does not include 

the firefighter opening the rear door to make entry to the structure and the subsequent exterior left 

wall fire penetration. The times of the ventilation changes are provided in Table 3.1. Structure leakage has been shown to be important when modeling enclosure fires [19]. The open front door at the 

start of the simulation and the vents (opening size and open time) created during the simulation are 

significantly larger than the total effective area of leakage of a structure of this type. Therefore, any 

leakage in the structure would have a negligible impact on the fluid mechanics within the structure 

and is not included in this study. 

An unknown parameter in Table 3.1 that needed to be estimated was the time when the second floor interior/porch door failed (160 s into the simulation). The area of failure was also estimated based on the following observations. The bottom hinge from the door appeared to be closed 

throughout the fire due to the lack of fire damage and the lack of soot deposited on the interior 

faces of the hinge and remaining wood, as shown in Fig. 3.3. It appears that the door collapsed 

and failed partially open. In the simulations, only the upper portion of the door was assumed to 

fail. While this time and area may not be exact, the takeaway from the analysis in the following 

sections should be impact of the door’s failure on the interior conditions of the structure. 

11
 
Table 3.1: Timeline of ventilation changes in the simulation
 

Baseline Alternative Ventilation Type Side of 

Simulation Simulation Area Structure 

[s] [s] [m2] 

0 0 0.11 Window Rear 

40 40 0.08 Breach (x2) Front and Rear 

45 45 0.12 Breach Left 

55 55 0.12 Breach Rear 

130 N/A∗ 1.41 Door Rear 

135 N/A∗ 0.2 Breach Left 

160 160 0.80 Door Interior 

∗These ventilation events were not included in the alternative simulation. 

Figure 3.3: Post-incident image of the second floor porch door frame that failed taken from inside 

the structure looking toward the porch. Note that the hinge is still intact and there is unburned, 

“clean” wood along the bottom portion of the frame. 

12
 
3.5 Numerical Mesh

For the simulation, a measure of how well the flow field is resolved can be estimated by using the 

non-dimensional expression D∗/δx. Here, D∗ is the characteristic fire diameter, δx is the nominal 

size of a mesh cell, and Q ̇ is the total heat release rate of the fire: 

� �

2

Q ̇ 5

D∗ = √ (3.2) ρ∞ cp T∞ g 

From the FDS User’s Guide [6], the characteristic fire diameter is related to the characteristic fire 

size via the relation Q∗ = (D∗/D)5/2. Here, D is the physical diameter of the base of the fire 

specified in the simulation. Following Eq. 3.2 and using a grid cell size of 10 cm, the characteristic 

fire diameter to cell size (D∗/δx) ratio is 15.5 for the 3.3 MW porch fire and 23 for the 9 MW attic 

fire. Based on validation work performed for the U.S. Nuclear Regulatory Commission, D∗/δx 

values ranged between 4 and 16 [20] and produced results that were adequate for engineering 

calculations. The grid resolution used in this model is within or exceeds typical engineering D∗/δx 

values. 

As discussed in Section 3.1, the structure has dimensions of 17.15 m (56 ft) by 6.15 m (20 ft) 

and a total height of 8.56 m (28 ft). To ensure adequately resolved fluid flow in and out of the 

structure, the computational domain was extended beyond the volume of the structure. The total 

volume of the computational domain was 24 m (79 ft) by 10 m (33 ft) by 10 m (33 ft). A grid 

resolution of 10 cm (3.9 in) was used, which required 2.4 million computational cells. As a result, 

all of the input model geometry lengths, ventilation openings (holes, doors, and windows), and 

fire areas will snap to the nearest 10 cm. Figure 3.4 shows the front of the structure rendered in 

Smokeview with the 10 cm mesh. The domain was divided into 16 equally sized meshes (each 

containing 150,000 grid cells) that could be processed in parallel, which reduced the amount of 

required calculation time to approximately 1.5 days. Figure 3.5 shows the entire structure within 

the computational domain that has been divided into multiple meshes. Table 3.2 shows a summary 

of the model input parameters for the simulations that were conducted as part of this study. 

13
 
Figure 3.4: Front (left) and rear (right) of the structure with 10 cm computational mesh.
 

Figure 3.5: Front-right side of the structure within the computational domain (with multiple 

meshes). Each of the 16 meshes is 3 m (9.8 ft) by 10 m (33 ft) by 5 m (16.4 ft). 

14
 
Table 3.2: Relevant fire model input parameters
 

Parameter Description Discussion
 

Simulation Time 5 min – 

Grid Cell Size 10 cm Section 3.5 

Ambient Temperature∗ 20 ◦C (68 ◦F) – 

Formula: CH1.7O0.74N0.002 

Reaction: Wood [14] CO Yield: 0.004 kg/kg 

Soot Yield: 0.015 kg/kg Section 3.2 

Heat of Combustion: 16,400 kJ/kg 

Peak HRR Attic Fire: 9 MW 

Porch Fire: 3.3 MW Section 3.2 

k: 0.12 W/(m ·K)) 

Material: Wood [18] ρ: 510 kg/m3 Section 3.3 

cp: 1.38 kJ/(kg ·K) 

k: 0.28 W/(m ·K) 

Material: Gypsum Board [17] ρ: 810 kg/m3 Section 3.3 

cp: 1.0 kJ/(kg ·K) 

∗Initial interior temperatures were assumed to be 20 ◦C; exterior temperatures were 7 ◦C [8]. 

15
 
Section 4

Model Results

To examine the results of the simulations, it is important to link the timelines from the fire scene 

to the simulation times. Table 4.1 shows the fireground timeline [8] along with the corresponding 

simulation times. 

4.1 Heat Release Rate

The heat release rate output data from FDS quantifies the simulated rate of energy release in the 

simulation. Figure 4.1 shows the prescribed HRR versus time values based on the prescribed fires 

along with the FDS results for the two ventilation scenarios that were described in Section 3.4. The 

two vertical lines represent the time at which a firefighter opened the back door of the structure (t 

= 130 s) and the time at which the second floor interior door was estimated to fail (t = 160 s). Due 

to a lack of information about the time of fire ignition or how fast the fire grew, these parameters 

needed to be estimated. The growth rate shown in Fig. 4.1 (10 MW in approximately 20 s) is fast 

because the incipient stage of the fire growth was not considered in this study. The maximum size 

of the fire used in this study was selected such that the conditions would become ventilation limited 

quickly to minimize computational time while aligning with the timeline observations of video and 

picture evidence from the fire. Using this approach, the accuracy of heat transfer to the walls of the 

structure may be sacrificed; however, all of the window, door, and wall failures were driven by the 

event timeline rather than failure temperature criteria. 

In Fig. 4.1, the solid line represents the baseline FDS simulation (this follows the noted door 

openings from the incident). The dashed line represents an alternative series of events in which the 

rear door does not get opened and the subsequent breach of the rear porch wall on the left side of 

the structure does not occur. The dash-dotted line represents the prescribed (or nominal) HRR that 

was input into FDS. As shown in Fig. 4.1, the HRR output from FDS is less than the prescribed 

HRR because the fire in the structure becomes ventilation limited. The maximum HRR value is 

slightly less than 9 MW before the fire becomes ventilation limited and begins to decay. The HRR 

is reduced to 5 MW as the oxygen inside the structure is consumed. There is an insufficient amount 

of oxygen in the structure to burn all of the fuel, therefore combustion occurs locally at the vents 

where fresh air is available. Figure 4.2 shows flaming combustion through the failed window on the 

rear side of the structure and attic breach just after the second fire ignites at 40 s. After additional 

16
 
Table 4.1: Fire incident and simulation event timeline
 

Incident Time Simulation Time Fire Behavior / Fireground Operation 

[hh:mm:ss] [s] 

Dispatch for a “Still” alarm - two engine companies, 17:16:00 two truck companies, and a battalion chief.
 

On-scene report of a working fire with heavy smoke
 17:17:00 coming from the front and rear of the structure’s attic. 

FDS simulation starts. Attic fire ignites. Initial 

0 ventilation through rear of structure. Front door 

open. 

Attic windows break - heavy smoke out of front attic 

17:20:00	 40 window and heavy smoke and fire out of rear. Rear 

porch ignites in model. 

Ventilation through wall penetration on rear of 45 

structure.
 

Ventilation through wall penetration on left side
 55 

of structure.
 

E123 captain and firefighter on second floor
 17:21:00 100 with 13⁄4-inch hoseline.
 

First floor exterior porch door opened. Porch
 17:21:30 130 fire ignites in FDS model. 

135 Ventilation through left side of structure. 

160 Top of interior door fails in FDS model. 

Heavy fire report in rear stairwell and enclosed 

17:23:00	 220 porch. No response from E123 captain or firefighter. 

17:24:00	 Water applied to attic from the rear exterior position. 

17:25:00	 SQ5 makes entry through front of structure. 

After hearing a Mayday call from SQ5, IC calls 17:27:00 300 a Mayday. Simulation ends. 

17:29:00	 E123 captain carried out of structure. 

For specific information regarding ventilation areas used in the FDS model, refer to Table 3.1. 

17 
0 50 100 150 200 250

Time (s)

0

5

10

15

20

HRR (MW)

Rear Door Open Interior Door Fail

Prescribed HRR

FDS Model HRR (Baseline Simulation)

FDS Model HRR (Alternative Simulation)

Figure 4.1: HRR versus time from the FDS simulations. The first vertical line indicates the time 

at which the back door failed (130 s), and the second vertical line indicates the time at which the 

interior hallway door failed (160 s). 

wall breaches occur at 45 s and 55 s (see Table 3.1), the abrupt change in ventilation causes the 

HRR to increase to 9 MW before it decreases to approximately 6 MW. The HRR then increases 

towards a sustainable steady-state value. 

Figure 4.1 indicates that the HRRs for both of the ventilation scenarios in FDS are identical 

until 130 s (HRR ≈ 7 MW). At 130 s, the rear door is opened in the baseline simulation. At 135 s, 

there is an additional breach on the left side of the structure (Table 3.1). The open door and breach 

act as additional pressure releases for the structure. Again, the abrupt change in ventilation causes 

the HRR to increase from approximately 7 MW to 9.7 MW at 139 s. At the time of the door 

failure (160 s), the HRR in both cases was approximately 9 MW because of the increased amount 

of ventilation. While there might be some locally different burning characteristics between the 

baseline simulation and the alternative simulation, the interior conditions in both cases presented 

a significant hazard to firefighters inside of the structure. Therefore, the analysis will focus on the 

results of the baseline simulation. 

18
 
Figure 4.2: Smokeview rendering of exterior combustion occurring on the rear side of the structure.
 

19
 
4.2 Pressure

As the simulated fire grows in the attic and rear porch, the pressure rises. Figure 4.3 shows the 

calculated pressure conditions in the structure just before the interior door failed in the simulation. 

On the rear porch, the pressure rise ranges from a 4 Pa (5.8 ×10−4 psi) over-pressure at a height of 

1 m to greater than 10 Pa (1.5 ×10−3 psi) at the ceiling. Gases at an elevated pressure will always 

move towards a region of lower pressure. The door serves as a boundary between the high and low 

pressure regions. Once the door fails open, the high pressure gases flow towards the low pressure 

regions in the house, hallway, kitchen, and front stairwell. The velocity vectors shown in Fig. 4.4 

(15 s after the interior door fails) indicate the direction of flow within the structure. 

Pressure 

Pa 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Figure 4.3: FDS simulated pressure contours, 1 s prior to interior door failure.
 

20
 
Velocity Velocity mph m/s 11 5 

10 

4.5 

9 4 8 

3.5 

7 3 6 

2.5 5 2 4 1.5 3 1 

21 

0.5 

0 0 

Figure 4.4: FDS simulated velocity vectors, 15 s after interior door failure. 

21
 
4.3 Temperature

Analysis of the temperatures from the FDS simulation focuses on the high hazard areas of the 

structure: the attic, the rear porch and stairwell, and the interior hallway which connects the rear 

porch to the front stairwell. The temperature profile at these high hazard areas is shown via several 

snapshots in time to illustrate the change in the interior conditions. The first snapshots are shown 

at a time of 129 s into the simulation, just before a firefighter opened the rear porch door (as shown 

in Fig. 4.5), and 159 s into the simulation, just before the interior door fails (as shown in Fig. 4.6). 

Temperature Temperature ◦F ◦C 

500 260 

240 455 

220 410 200 

365 180 

320 160 

140 275 

120 230 100 

185 80 

140 60 

77 25

Figure 4.5: FDS simulated temperature contours, 1 s prior to rear door opening. 

Temperature Temperature ◦F ◦C 

500 260 

240 455 

220 410 200 

365 180 

320 160 

140 275 

120 230 100 

185 80 

140 60 

77 25

Figure 4.6: FDS simulated temperature contours, 1 s prior to interior door failure. 

Figure 4.5 shows temperatures of at least 260 ◦C (500 ◦F) in the second floor rear porch and 

rear portion of the attic. In this figure, the lower temperature bound is set to 25 ◦C (77 ◦F), and 

the upper temperature bound is set to 260 ◦C (500 ◦F); however, these are only limits on the 

visualized output, and the actual simulated temperatures may exceed the lower or upper bounds. 

22
 
High temperatures, between 80 ◦C (185 ◦F) and 200 ◦C (390 ◦F), also extend down to the rear 

entrance on the first floor. Before the interior door fails (Fig. 4.6), the inflow of ambient air from 

the open rear door reduces the temperatures near the interior doorway, but at the same time, the 

HRR increases because of the additional ventilation, as shown in Fig. 4.1. As shown in Fig. 4.7, 

after the second floor interior door fails, the high temperature gas that filled the rear porch flows 

in the direction of lower pressure (i.e., towards the front door). Note that the conditions in the attic 

do not appear to change. 

Temperature Temperature ◦F ◦C 

500 260 

240 455 

220 410 200 

365 180 

320 160 

140 275 

120 230 100 

185 80 

140 60 

77 25

Figure 4.7: FDS simulated temperature contours, 1 s after interior door failure. 

Temperature Temperature ◦F ◦C 

500 260 

240 455 

220 410 200 

365 180 

320 160 

140 275 

120 230 100 

185 80 

140 60 

77 25 

Figure 4.8: FDS simulated temperature contours, 15 s after the interior door failure. 

As shown in Fig. 4.8, 15 s after the door failed, high temperature gases descended to approximately 1 m (3.28 ft) above the floor through the interior hallway and are flowing into the kitchen. 

23
 
Section 5

Discussion of Simulation Results

The results of the FDS simulations are discussed in the following two sections. The first section 

addresses the results of the computational modeling as they relate to the interior hallway’s conditions. The second section examines the model results and observed outcomes of the fire incident 

as they relate to tactics discussed in recent experimental research. 

5.1 Simulated Hallway Flow Path

From on-scene reports (Section 2) and the FDS simulation results (Section 4.3), the interior conditions on the second floor of the structure were initially tenable. From the NIOSH report [8], 

while the IC was inside the structure on the second floor, only light haze and a glow around the 

door between the hallway and enclosed porch was observed. This indicated the presence of fire in 

the area of the enclosed porch. The simulation results indicate a high hazard area (temperatures 

greater than 260 ◦C or 500 ◦F) in the attic and the enclosed porch at this time. By the time the 

E123 captain and firefighter arrived on the second floor (Table 4.1) and approached the rear of the 

structure, the rear porch was fully involved. Temperature conditions greater than 260 ◦C (500 ◦F) 

were present on the porch side of the steel-faced, wood-framed door at the rear of the structure. 

Exposure to these conditions likely weakened the structural integrity of the door, which may have 

led to a partial failure (Table 4.1). Figure 5.1 shows the state of the rear door after the fire. Note the 

large crease in the steel face of the door just above the knob. 

Recent experiments conducted by NIST revealed similar post-fire states after doors of similar construction were exposed to fires. Figure 5.2 shows doors from two different residential fire 

experiments in different stages of degradation. In both cases, note that the door knob assembly 

served as a pivot point for the upper portion of the door to collapse around. This is similar to the 

location of the creases in the remains of the steel door that was located between the hallway and 

the enclosed porch in this fire incident. 

After the interior door failed, an interior flow path was created from the enclosed porch area 

into the kitchen of the structure. This resulted in a rapid change in the conditions within the flow 

path. The combustion gases at elevated temperature and pressure in the enclosed porch were vented 

by the failure of the door and flowed towards lower pressure areas in the hallways and kitchen. The 

arrows shown in Fig. 5.3 summarize the simulated flow direction of gases on the second floor 

24
 
Figure 5.1: Post-fire image of interior door.
 

Figure 5.2: Post-experiment images of door failures. 

after the door failure. In this figure, the red arrows indicate elevated gas temperatures, and the 

blue arrows indicate relatively cooler gas temperatures. The arrow that transitions from red to blue 

indicates that the heated gases were cooling as they flowed away from the fire towards the front 

of the structure. The two arrows located at the door on the second floor (towards the front of the 

structure) indicate bi-directional flow. At that doorway, cool ambient air flowed towards the fire 

near the bottom of the door, and hot gases flowed away from the fire near the top of the door. 

25
 
Figure 5.3: Summary of simulated flow path on the second floor after interior door failure.
 

26
 
5.2 Assessing the Hazard

A person is susceptible to second-degree burn injuries if exposed to temperatures greater than 

55 ◦C (130 ◦F) [21]. Although firefighters wear protective gear, gear only offers a finite amount 

of protection. The polycarbonate in a self contained breathing apparatus begins to soften when the 

material temperature reaches approximately 140 ◦C (284 ◦F) [22]. Structural fire fighting coats 

and pants are tested to withstand temperatures of 260 ◦C (500 ◦F) [23]. Prolonged exposure to 

elevated temperatures can result in a significant amount of heat transferred to the firefighter, putting 

him/her at risk. Exposure of equipment to temperatures of 260 ◦C (500 ◦F) represents a Class 

III exposure [24]. Firefighters are at increased risk levels when encountering Class III exposure 

conditions for more than 5 minutes [24]. Therefore, for the analysis of the simulated exposure 

temperatures, the maximum visualized temperature is set to indicate all values that are greater than 

or equal to 260 ◦C (500 ◦F). This means that temperatures visualized at the maximum range in the 

displayed model output are at a minimum of 260 ◦C (500 ◦F); the actual simulated temperatures 

could in fact be greater. 

Prior to the interior door failure, the elevated temperatures on the second floor were limited to 

the rear porch, as shown in Fig. 5.4. The temperatures were greatest at the back-left corner where 

there is sufficient oxygen due to the section of porch wall that had burned away and allowed additional oxygen to mix with the fuel-rich fire gases. Five seconds after the interior door failed, 

hot gases traveled the length of the interior hallway and approached the doorway into the kitchen, 

which was approximately 4.5 m (14.8 ft) away from the source fire, as shown in Fig. 5.5. Within 

60 s of the interior door failure, the hallway temperatures were approximately at or above 260 ◦C 

(500 ◦F) throughout the hallway, as shown in Fig. 5.6. These results indicate that the high temperature gases seen 5 s after failure were not just a burst but rather the front of a sustained exhaust 

gas flow from the fire burning in the enclosed rear porch. The conditions in this hallway changed 

from tenable to high-hazard very rapidly following the door failure. Figure 5.6 also shows that the 

temperatures in the kitchen were at or below 90 ◦C (194 ◦F), and the temperatures at the top of the 

stairs were at or below 70 ◦C (158 ◦F). At these locations within the structure, the exhaust gases in 

the flow path were cooled and diluted by the inflowing ambient gas. These simulated temperatures 

are consistent with the post-incident conditions that were documented in the kitchen and second 

floor stairwell. 

27
 
Temperature Temperature ◦F ◦C 

500 260 

240 455 

220 410 200 

365 180 

320 160 

140 275 

120 230 100 

185 80 

140 60 

77 25

Figure 5.4: Temperature contours on the second floor, 1 s prior to interior door failure, 1.83 m (6 ft) 

above the floor. 

Temperature Temperature ◦F ◦C 

500 260 

240 455 

220 410 200 

365 180 

320 160 

140 275 

120 230 100 

185 80 

140 60 

77 25

Figure 5.5: Temperature contours on the second floor, 5 s after interior door failure, 1.83 m (6 ft) 

above the floor. 

28
 
Temperature Temperature ◦F ◦C 

500 260 

240 455 

220 410 200 

365 180 

320 160 

140 275 

120 230 100 

185 80 

140 60 

77 25

Figure 5.6: Temperature contours on the second floor, 60 s after interior door failure, 1.83 m (6 ft) 

above the floor. 

29
 
5.3 Tactical Considerations

There have been many previous fire incidents [8, 25–38] in which changes in the flow paths are 

thought to have had an adverse impact on firefighter and occupant safety. Table 5.1 lists the NIOSH 

investigation reports from the past 15 years in which it could be determined that a flow path played 

a role in the related incident. This table lists the NIOSH investigation number, the outcome, and a 

brief description of the flow path details. 

Based on a review of these incidents, it is clear that fires with rapidly developing or changing 

flow paths are a significant hazard to the fire service. The development of (or changes to) a flow 

path could be caused by the failure of a component of the structure, such as a door, window, or 

portion of a ceiling, wall or floor. Environmental conditions such as wind can generate hazardous 

thermal conditions within a flow path. Uncoordinated ventilation can also be the cause of increased 

thermal hazards within a flow path. 

In this fire incident, the thermal degradation of the steel-faced, wood-framed door resulted 

in a rapid change in the thermal conditions in the hallway, which resulted in highly hazardous 

conditions. These conditions would be equivalent to or greater than a Class III exposure [24]. 

Prediction of the failure mode and failure time of the door is not a reasonable expectation given the 

large number of unknowns that the firefighters faced on the fire ground. In this case, the timing of 

the interior attack appears to have coincided with the failure time of the door. Research has been 

conducted [39, 40] and continues to be conducted by NIST, Underwriters Laboratories (UL), and 

others that demonstrates that applying water from the exterior into the fire area of a structure (prior 

to the start of interior operations) can significantly improve the safety of firefighters by reducing 

the thermal hazard from the fire and reducing the potential for developing high velocity hot gas 

flows within the structure. 

30
 
Table 5.1: Flow path related LODD/LODI incidents
 

NIOSH Report No. No. of LODDs/LODIs Flow Path Details 

99-F01 [25] 3 LODDs From apartment into hallway on 10th 

floor of high-rise apartment building 

99-F21 [26] 2 LODDs Basement to 1st floor 

2 LODIs 

F2000-04 [27] 3 LODDs 1st floor to 2nd floor 

3 civilian deaths 

F2000-16 [28] 1 LODD 2nd floor hallway through 

1 LODI 2nd floor apartment 

1 civilian death 

F2000-23 [29] 1 LODD From ground level to 1st floor then to 

2 LODIs 2nd floor, flow exited through ceiling 

F2000-43 [30] 1 serious LODI 1st floor to 2nd floor 

2 other LODIs 

F2004-02 [31] 1 LODD 1st floor to basement 

F2005-02 [32] 1 LODD Rear to front of the building 

4 LODIs 

F2005-04 [33] 1 LODD Basement to 1st floor 

9 LODIs 

F2007-09 [34] 1 LODD 3 story training burn - flow through 

2 LODIs all levels 

F2007-35 [35] 4 LODIs 1st floor to 2nd floor 

F2009-11 [36] 2 LODDs Rear to front of the building 

F2011-13 [37] 2 LODDs Lower level up stairs and through 

entry door and garage 

F2011-31 [38] 1 LODD Fire extended from lower level apartment 

F2012-28 [8] 1 LODD Attic fire extended into closed 

1 LODI porch and then into 2nd floor 

31
 
Section 6

Summary

NIST’s Fire Dynamics Simulator was used to provide insight into the fire dynamics within a 

2 1⁄2 story single family structure in Chicago, IL, that resulted in the death of the captain of a fire 

department. The fuel, fire size, and fire growth rate that were used in the FDS simulations were estimated by taking into account all of the available information including the NIOSH post-incident 

report [8], post-incident pictures, videos, and relevant literature. This resulted in a specified source 

fire of 12.3 MW in the attic and rear porch of the structure. However, based on the limited ventilation conditions in the attic and enclosed porch, the FDS simulation results indicated a maximum 

HRR of approximately 9 MW as a result of the limited supply of oxygen. 

The fire started in the attic and spread down into the enclosed porch on the rear of the structure. 

The spread of fire and hot gases into the second floor of the structure was limited by a closed 

steel-faced, wood-framed door that was located between the enclosed porch and the hallway. After 

exposure to the elevated temperatures and pressure from the fire in the porch area, the wood frame 

of the door decomposed and the steel faces of the door failed and collapsed inward. The door failure 

resulted in the establishment of a flow path between the higher pressure and higher temperature 

conditions in the enclosed porch and the lower pressure and lower temperature conditions in the 

hallway and kitchen areas of the second floor. The temperature of the gases that flowed into the 

hallway at face height was calculated to exceed 260 ◦C (500 ◦F). Unfortunately, a captain and 

firefighter were advancing a hose line in the hallway at the time of the door failure. The captain 

was overcome by the rapid change in conditions before he could exit to the safety of the kitchen 

area. After a Mayday call, the captain was rescued from the structure but later succumbed to his 

injuries. 

32
 
Acknowledgments

The authors would like to thank the Chicago Fire Department, especially Commissioner Jose Santiago, District Chief Donald Hroma, and District Chief Kevin Krasneck. The authors would also 

like to thank John Culbertson of Central Valley Fire District, MT, for his assistance in compiling 

Table 5.1. Finally, the authors would also like to thank Keith Stakes of NIST and Joseph Willi of 

the University of Illinois Urbana-Champaign for their assistance in creating the drawings of the 

structure. 

33
 
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37
 
Appendix A

Dimensioned Drawings

1

1

2

2

A A

B B

Legend

Symbol Meaning

 CH is 2.54

.74 X 2.03 

door

door

window

17.15

1.59

3.30

5.89

7.80

8.84

10.17

11.28

14.97

15.61

2.41

2.53

2.84

3.61

1.70

5.13

6.35

9.07

11.90

1.37

2.90

3.66

3.85

5.07

5.45

6.15 .86 1.54 .33

1.04

.28 1.42

.30

.46

1.08

.86

.84 X 

1.79

.66 X 1.22

(.86 off floor) .97 wide with 

.24 run & .18 rise

.79 X 1.35

(.86 off floor)

.46 X .66 

(1.02 off 

floor)

.67 X 1.7

(.71 off floor)

.67 X 1.6 

(.79 

above 

floor)

.89 X 2.11

.91 wide 

.18 rise 

& .27 run 

(17 stairs 

in total)

1.29 X 

2.03

2315 West 50th Place

1st Floor

*Units are in meters

*CH is 2.68 unless noted

*Outside walls are .17 thick

*Inside walls are .11 or .15 thick

A

C

Figure A.1: Dimensioned drawing of first floor. The measurements are accurate to within 15 cm 

(6 in). 

38
 
1

1

2

2

A A

B B

1.37

2.90

3.35

3.85

4.32

4.81

5.07

5.60

6.15

C

A

4.38

5.95

7.86

10.17

10.48

11.30

14.52

1.45

2.38

3.59

4.31

1.52

4.58

2.58

2.77

3.81

4.73

5.85

7.44

9.55

11.07

11.30

12.92

13.74

16.01

.22

1.37

3.73

11.55

.08 1.23

2.32 2.88

.33

Legend

Symbol Meaning

.67 X 1.60 window 

(.79 above floor)

.79 X 1.35 window 

(.86 above floor) 

 2.84 CH

 2.41 CH

stairs

 .79 X 2.03 door

.61 X 2.03 door

1.29 X 2.03 door

 .76 X 2.03 door

.68 X 1.99 door

.88 X 2.08 doorway

 .71 X 2.03

8.86

14.97

2312 West 50th Place

2nd Floor

*All units are in meters

*CH is 2.56 unless noted

*Outside walls are .17 thick

*Inside walls are .11 or .15 

thick

17.15

.30

Figure A.2: Dimensioned drawing of second floor. The measurements are accurate to within 15 cm 

(6 in). 

39