NIST Technical Note 1661

Jason D. Averill

Lori Moore-Merrell

Adam Barowy

Robert Santos

Richard Peacock

Kathy A. Notarianni

Doug Wissoker

Edited by Bill Robinson

U.S. Department of Commerce

Gary Locke, Secretary

National Institute of Standards and Technology

Patrick D. Gallagher, Director

April 2010 1
2
April 2010

NIST Technical Note 1661

Report on Residential

Fireground Field Experiments

Jason D. Averill

Lori Moore-Merrell

Adam Barowy

Robert Santos

Richard Peacock

Kathy A. Notarianni

Doug Wissoker

Edited by Bill Robinson

U.S. Department of Commerce

Gary Locke, Secretary

National Institute of Standards and Technology

Patrick D. Gallagher, Director

3
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.

4
National Institute of Standards and Technology Technical Note 1661,

104 pages (March 2010) CODEN:

Produced with the Cooperation of

Montgomery County

Fire and Rescue

Chief Richard Bowers

Produced with the Cooperation of

Fairfax County

Fire and Rescue

Chief Ronald Mastin

Funding provided through DHS/FEMA Grant Program Directorate for FY 2008

Assistance to Firefighters Grant Program – Fire Prevention and Safety Grants

(EMW-2008-FP-01603)

5
6
Table of Contents

Abstract ................................................................................................9

Executive Summary ..........................................................................10

Background........................................................................................12

Problem ..............................................................................................13

Review of Literature ..........................................................................14

Purpose and Scope of the Study ....................................................16

A Brief Overview of Fire Department Fireground Operations....17

The Relation of Time-to-Task Completion and Risk ..........................18

Standards of Response Cover............................................................18

Part 1: Planning for the Field Experiments....................................20

Part 2: Time-to-Task Experiments ..................................................24

Field Experiment Methods ..............................................................21

Field Site ..............................................................................................21

Overview of Field Experiments ..........................................................22

Instrumentation ....................................................................................22

Safety Protocols ..................................................................................23

Crew Size ............................................................................................24

Department Participation ....................................................................24

Crew Orientation..................................................................................24

Tasks ....................................................................................................25

Data Collection: Standardized Control Measures..............................27

Task Flow Charts and Crew Cue Cards ............................................27

Radio communications ........................................................................27

Task Timers ..........................................................................................27

Video records ......................................................................................27

Crew Assignment ................................................................................28

Response Time Assumptions..............................................................28

Part 3: Room and Contents Fires....................................................29

Fuel Packages for the Room and Contents Fires..............................29

Experimental Matrix for Room and Contents Fires............................30

Procedure for Minimizing the Effect of Variance in Fire Growth Rate ..........31

Analysis of Experimental Results ..................................................33

Time-to-task Analysis ..........................................................................33

Data Queries........................................................................................33

Statistical Methods - Time to Task ......................................................33

Regression Analysis ............................................................................33

Measurement Uncertainty ..................................................................34

How to Interpret Time-to-Task Graphs................................................34

Time-to-Task Graphs ..........................................................................35

Part 4: Fire Modeling ........................................................................43

Time to Untenable Conditions: Research Questions ........................45

Fire Modeling Methods........................................................................45

Fire Growth Rates................................................................................46

Fractional Effective Dose (FED)..........................................................47

Results from Modeling Methods ........................................................48

Interior Firefighting Conditions and Deployment Configuration ........49

Physiological Effects on Firefighters: Comparison by Crew Size........50

Study Limitations ..............................................................................51

Conclusions........................................................................................52

Future Research ................................................................................53

Acknowledgments ............................................................................55

References..........................................................................................56

7
8
Service expectations placed on the fire service, including

Emergency Medical Services (EMS), response to natural

disasters, hazardous materials incidents, and acts of

terrorism, have steadily increased. However, local

decision-makers are challenged to balance these community

service expectations with finite resources without a solid technical

foundation for evaluating the impact of staffing and deployment

decisions on the safety of the public and firefighters.

For the first time, this study investigates the effect of varying

crew size, first apparatus arrival time, and response time on

firefighter safety, overall task completion, and interior residential

tenability using realistic residential fires. This study is also unique

because of the array of stakeholders and the caliber of technical

experts involved. Additionally, the structure used in the field

experiments included customized instrumentation; all related

industry standards were followed; and robust research methods

were used. The results and conclusions will directly inform the

NPFA 1710 Technical Committee, who is responsible for

developing consensus industry deployment standards.

This report presents the results of more than 60 laboratory and

residential fireground experiments designed to quantify the

effects of various fire department deployment configurations on

the most common type of fire — a low hazard residential

structure fire. For the fireground experiments, a 2,000 sq ft (186

m2), two-story residential structure was designed and built at the

Montgomery County Public Safety Training Academy in

Rockville, MD. Fire crews from Montgomery County, MD and

Fairfax County,VA were deployed in response to live fires within

this facility. In addition to systematically controlling for the

arrival times of the first and subsequent fire apparatus, crew size

was varied to consider two-, three-, four-, and five-person staffing.

Each deployment performed a series of 22 tasks that were timed,

while the thermal and toxic environment inside the structure was

measured. Additional experiments with larger fuel loads as well as

fire modeling produced additional insight. Report results quantify

the effectiveness of crew size, first-due engine arrival time, and

apparatus arrival stagger on the duration and time to completion

of the key 22 fireground tasks and the effect on occupant and

firefighter safety.

Abstract

9
Both the increasing demands on the fire service -such as the

growing number of Emergency Medical Services(EMS)

responses, challenges from natural disasters, hazardous

materials incidents, and acts of terrorism — and previousresearch

point to the need forscientifically based studies of the effect of

different crew sizes and firefighter arrival times on the effectiveness of

the fire service to protect lives and property. To meet this need, a

research partnership of the Commission on FireAccreditation

International(CFAI),InternationalAssociation of Fire Chiefs(IAFC),

InternationalAssociation of Firefighters(IAFF), National Institute of

Standards and Technology (NIST), and Worcester Polytechnic

Institute (WPI) was formed to conduct a multiphase study of the

deployment of resources as it affects firefighter and occupant safety.

Starting in FY 2005, funding was provided through the Department of

Homeland Security (DHS)/ Federal Emergency ManagementAgency

(FEMA) Grant Program Directorate forAssistance to Firefighters

Grant Program — Fire Prevention and Safety Grants.In addition to

the low-hazard residential fireground experiments described in this

report,the multiple phases of the overallresearch effort include

development of a conceptual model for community risk assessment

and deployment of resources, implementation of a generalizable

department incident survey, and delivery of a software tool to quantify

the effects of deployment decisions on resultant firefighter and civilian

injuries and on property losses.

The first phase of the project was an extensive survey of more than

400 career and combination (both career and volunteer) fire

departments in the United States with the objective of optimizing a

fire service leader’s capability to deploy resources to prevent or

mitigate adverse events that occur in risk- and hazard-filled

environments. The results of this survey are not documented in this

report, which is limited to the experimental phase of the project.

The survey results will constitute significant input into the

development of a future software tool to quantify the effects of

community risks and associated deployment decisions on resultant

firefighter and civilian injuries and property losses.

The following research questions guided the experimental

design of the low-hazard residential fireground experiments

documented in this report:

1. How do crew size and stagger affect overall start-to-completion

response timing?

2. How do crew size and stagger affect the timings of task

initiation, task duration, and task completion for each of the 22

critical fireground tasks?

3. How does crew size affect elapsed times to achieve three critical

events that are known to change fire behavior or tenability

within the structure:

a. Entry into structure?

b. Water on fire?

c.Ventilation through windows (three upstairs and one back

downstairs window and the burn room window).

4. How does the elapsed time to achieve the national standard of

assembling 15 firefighters at the scene vary between crew sizes

of four and five?

In order to address the primary research questions, the research

was divided into four distinct, yet interconnected parts:

 Part 1 — Laboratory experiments to design appropriate fuel load

 Part 2 — Experiments to measure the time for various crew

sizes and apparatus stagger (interval between arrival of

various apparatus) to accomplish key tasks in rescuing

occupants, extinguishing a fire, and protecting property

 Part 3 — Additional experiments with enhanced fuel load that

prohibited firefighter entry into the burn prop – a building

constructed for the fire experiments

 Part 4 — Fire modeling to correlate time-to-task completion

by crew size and stagger to the increase in toxicity of the

atmosphere in the burn prop for a range of fire growth rates.

The experiments were conducted in a burn prop designed to

simulate a low-hazard1 fire in a residential structure described as

typical in NFPA 1710® Organization and Deployment of Fire

Suppression Operations, Emergency Medical Operations, and Special

Operations to the Public by Career Fire Departments. NFPA 1710 is

the consensus standard for career firefighter deployment,

including requirements for fire department arrival time, staffing

levels, and fireground responsibilities.

Limitations of the study include firefighters’ advance knowledge

of the burn prop, invariable number of apparatus, and lack of

experiments in elevated outdoor temperatures or at night. Further,

the applicability of the conclusions from this report to commercial

structure fires, high-rise fires, outside fires, terrorism/natural

disaster response, HAZMAT or other technical responses has not

been assessed and should not be extrapolated from this report.

Primary Findings

Of the 22 fireground tasks measured during the experiments,

results indicated that the following factors had the most

significant impact on the success of fire fighting operations. All

differential outcomes described below are statistically significant

at the 95 % confidence level or better.

Overall Scene Time:

The four-person crews operating on a low-hazard structure fire

completed all the tasks on the fireground (on average) seven

minutes faster — nearly 30 % — than the two-person crews. The

four-person crews completed the same number of fireground

tasks (on average) 5.1 minutes faster — nearly 25 % — than the

three-person crews. On the low-hazard residential structure fire,

adding a fifth person to the crews did not decrease overall

fireground task times. However, it should be noted that the

1 A low-hazard occupancy is defined in the NFPA Handbook as a one-, two-, or three-family dwelling and some small businesses. Medium hazards occupancies include

apartments, offices, mercantile and industrial occupancies not normally requiring extensive rescue or firefighting forces. High-hazard occupancies include schools,

hospitals, nursing homes, explosive plants, refineries, high-rise buildings, and other highlife hazard or large fire potential occupancies.

Executive Summary

10
2 NFPA Standard 1710 - A.5.2.4.2.1 ...Other occupancies and structures in the community that present greater hazards should be addressed by additional fire fighter

functions and additional responding personnel on the initial full alarm assignment.

3 NFPA 1710 Standard for the Organization and Deployment of Fire Suppression Operations, Emergency Medical Operations, and Special Operations to the Public by

Career Fire Departments. Section 5.2.1 – Fire Suppression Capability and Section 5.2.2 Staffing.

4 As defined in the handbook, a fast fire grows exponentially to 1.0 MW in 150 seconds. A medium fire grows exponentially to 1 MW in 300 seconds. A slow fire grows

exponentially to 1 MW in 600 seconds. A 1 MW fire can be thought-of as a typical upholstered chair burning at its peak. A large sofa might be 2 to 3 MWs.

benefit of five-person crews has been documented in other

evaluations to be significant for medium- and high-hazard

structures, particularly in urban settings, and is recognized in

industry standards.

2

Time to Water on Fire:

There was a 10% difference in the “water on fire” time between

the two- and three-person crews. There was an additional 6%

difference in the "water on fire" time between the three- and

four-person crews. (i.e., four-person crews put water on the fire

16% faster than two person crews). There was an additional 6%

difference in the “water on fire” time between the four- and

five-person crews (i.e. five-person crews put water on the fire 22%

faster than two-person crews).

Ground Ladders and Ventilation:

The four-person crews operating on a low-hazard structure fire

completed laddering and ventilation (for life safety and rescue)

30 % faster than the two-person crews and 25 % faster than the

three-person crews.

Primary Search:

The three-person crews started and completed a primary search

and rescue 25 % faster than the two-person crews. The four- and

five-person crews started and completed a primary search 6 %

faster than the three-person crews and 30 % faster than the

two-person crew. A 10 % difference was equivalent to just over

one minute.

Hose Stretch Time:

In comparing four-and five-person crews to two-and

three-person crews collectively, the time difference to stretch a line

was 76 seconds. In conducting more specific analysis comparing

all crew sizes to the two-person crews the differences are more

distinct. Two-person crews took 57 seconds longer than

three-person crews to stretch a line. Two-person crews took

87 seconds longer than four-person crews to complete the same

tasks. Finally, the most notable comparison was between

two-person crews and five-person crews — more than 2 minutes

(122 seconds) difference in task completion time.

Industry Standard Achieved:

As defined by NFPA 1710, the “industry standard achieved”

time started from the first engine arrival at the hydrant and ended

when 15 firefighters were assembled on scene.

3 An effective

response force was assembled by the five-person crews three

minutes faster than the four-person crews. Based on the study

protocols, modeled after a typical fire department apparatus

deployment strategy, the total number of firefighters on scene in

the two- and three-person crew scenarios never equaled 15 and

therefore the two- and three-person crews were unable to

assemble enough personnel to meet this standard.

Occupant Rescue:

Three different “standard” fires were simulated using the Fire

Dynamics Simulator (FDS) model. Characterized in the

Handbook of the Society of Fire Protection Engineers as slow-,

medium-, and fast-growth rate4, the fires grew exponentially with

time. The rescue scenario was based on a non-ambulatory

occupant in an upstairs bedroom with the bedroom door open.

Independent of fire size, there was a significant difference between

the toxicity, expressed as fractional effective dose (FED), for

occupants at the time of rescue depending on arrival times for all

crew sizes. Occupants rescued by early-arriving crews had less

exposure to combustion products than occupants rescued by

late-arriving crews. The fire modeling showed clearly that

two-person crews cannot complete essential fireground tasks in time

to rescue occupants without subjecting them to an increasingly toxic

atmosphere. For a slow-growth rate fire with two-person crews, the

FED was approaching the level at which sensitive populations,such

as children and the elderly are threatened. For a medium-growth

rate fire with two-person crews, the FED was far above that

threshold and approached the level affecting the general population.

For a fast-growth rate fire with two-person crews, the FED was well

above the median level at which 50 % of the general population

would be incapacitated. Larger crews responding to slow-growth

rate fires can rescue most occupants prior to incapacitation along

with early-arriving larger crews responding to medium-growth rate

fires. The result for late-arriving (two minutes later than

early-arriving) larger crews may result in a threat to sensitive

populations for medium-growth rate fires. Statistical averages

should not, however, mask the fact that there is no FED level so low

that every occupant in every situation is safe.

Conclusion:

More than 60 full-scale fire experiments were conducted to

determine the impact of crew size, first-due engine arrival time, and

subsequent apparatus arrival times on firefighter safety and

effectiveness at a low-hazard residential structure fire. This report

quantifies the effects of changes to staffing and arrival times for

residential firefighting operations. While resource deployment is

addressed in the context of a single structure type and risk level, it is

recognized that public policy decisions regarding the cost-benefit of

specific deployment decisions are a function of many other factors

including geography, local risks and hazards, available resources, as

well as community expectations. This report does not specifically

address these other factors.

The results of these field experiments contribute significant

knowledge to the fire service industry. First, the results provide a

quantitative basis for the effectiveness of four-person crews for

low-hazard response in NFPA 1710. The results also provide valid

measures of total effective response force assembly on scene for

fireground operations, as well as the expected performance

time-to-critical-task measures for low-hazard structure fires.

Additionally, the results provide tenability measures associated

with a range of modeled fires.

Future research should extend the findings of this report in

order to quantify the effects of crew size and apparatus arrival

times for moderate- and high-hazard events, such as fires in

high-rise buildings, commercial properties, certain factories, or

warehouse facilities, responses to large-scale non-fire incidents, or

technical rescue operations.

11
The fire service in the United States has a deservedly proud

tradition of service to community and country dating back

hundreds of years. As technology advances and the scope

of service grows (e.g., more EMS obligations and growing

response to natural disasters, hazardous materials incidents, and

acts of terrorism), the fire service remains committed to a core

mission of protecting lives and property from the effects of fire.

Firefighting is a dangerous business with substantial financial

implications. In 2007, U.S. municipal fire departments responded

to an estimated 1,557,500 fires. These fires killed 3,430 civilians

(non-firefighters) and contributed to 17,675 reported civilian fire

injuries. Direct property damage was estimated at $14.6 billion

dollars (Karter, 2008). In spite of the vigorous nationwide efforts

to promote firefighter safety, the number of firefighter deaths has

consistently remained tragically high. In both 2007 and 2008, the

U.S. Fire Administration reported 118 firefighter fatalities (USFA

2008).

Although not all firefighter deaths occur on the fireground —

accidents in vehicles and training fatalities add to the numbers —

every statistical analysis of the fire problem in the United States

identifies residential structure fires as a key component in

firefighter and civilian deaths, as well as direct property loss.

Consequently, community planners and decision-makers need

tools for optimally aligning resources with the service

commitments needed for adequate protection of citizens.

Background

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Despite the magnitude of the fire problem in the United

States, there are no scientifically based tools available to

community and fire service leaders to assess the effects of

prevention, fixed sprinkler systems, fire fighting equipment, or

deployment and staffing decisions. Presently, community and fire

service leaders have a qualitative understanding of the effect of

certain resource allocation decisions. For example, a decision to

double the number of firehouses, apparatus, and firefighters

would likely result in a decrease in community fire losses, while

cutting the number of firehouses, apparatus, and firefighters

would likely yield an increase in the community fire losses, both

human and property. However, decision-makers lack a sound

basis for quantifying the total impact of enhanced fire resources

on the number of firefighter and civilian lives saved and injuries

prevented.

Studies on adequate deployment of resources are needed to

enable fire departments, cities, counties, and fire districts to

design an acceptable level of resource deployment based upon

community risks and service provision commitment. These

studies will assist with strategic planning and municipal and state

budget processes. Additionally, as resource studies refine data

collection methods and measures, both subsequent research and

improvements to resource deployment models will have a sound

scientific basis.

Problem

13
Research to date has documented a consistent relationship

between resources deployed and firefighter and civilian

safety. Studies documenting engine and ladder crew

performance in diverse simulated environments as well as actual

responses show a basic relationship between apparatus staffing

levels and a range of important performance variables and

outcome measurements such as mean on-scene time, time-to-task

completion, incidence of injury among fire service personnel, and

costs incurred as a result of on-scene injuries (Cushman 1981,

McManis 1984, Morrison 1990, Ontario 1991, Phoenix 1991,

Roberts 1993).

Reports by fire service officials and consulting associates

reviewing fire suppression and emergency response by fire crews

in U.S. cities were the first publications to describe the

relationship between adequate staffing levels and response time,

time to completion of various fireground tasks, overall

effectiveness of fire suppression, and estimated value of property

loss for a wide range of real and simulated environments. In 1980,

the Columbus Fire Division’s report on firefighter effectiveness

showed that for a predetermined number of personnel initially

deployed to the scene of a fire, the proportion of incidents in

which property loss exceeded $5,000 and horizontal fire spread of

more than 25 sq ft (2.3 m2) was significantly greater for crews

whose numbers fell below the set thresholds of 15 total fireground

personnel at residential fires and 23 at large-risk fires (Backoff

1980). The following year, repeated live experiments at a

one-family residential site using modern apparatus and

equipment demonstrated that larger units performed tasks and

accomplished knockdown more quickly, ultimately resulting in a

lower percentage of loss attributable to factors controlled by the

fire department. The authors of this article highlighted that the

fire company is the fire department’s basic working unit and

further emphasized the importance of establishing accurate and

up-to-date performance measurements to help collect data and

develop conclusive strategies to improve staffing and equipment

utilization (Gerard 1981).

Subsequent reports from the United States Fire Administration

(USFA) and several consulting firms continued to provide

evidence for the effects of staffing on fire crews’ ability to

complete tasks involved in fire suppression efficiently and

effectively. Citing a series of tests conducted in 1977 by the Dallas

Fire Department that measured the time it took three-, four-, and

five-person teams to advance a line and put water on a simulated

fire at the rear of the third floor of an old school, officials from the

USFA underscored that time-to-task completion and final level of

physical exhaustion for crews markedly improved not after any

one threshold, but with the addition of each new team member.

This report went on to outline the manner in which simulated

tests exemplify a clear-cut means to record and analyze the

resources initially deployed and finally utilized at fire scenes (NFA

1981). A later publication detailing more Dallas Fire Department

simulations — ninety-one runs each for a private residential fire,

high-rise office fire, and apartment house fire — showed again

that increased staffing levels greatly enhanced the coordination

and effectiveness of crews’ fire suppression efforts during a finite

time span (McManis Associates 1984). Numerous studies of local

departments have supported this conclusion using a diverse

collection of data, including a report by the National Fire

Academy (NFA) on fire department staffing in smaller

communities, which showed that a company crew staffed with

four firefighters could perform rescue of potential victims

approximately 80 % faster than a crew staffed with three

firefighters (Morrison 1990).

During the same time period that the impact of staffing levels on

fire operations was gaining attention, investigators began to

question whether staffing levels could also be associated with the

risk of firefighter injuries and the cost incurred as a result of such

injuries at the fire scene. Initial results from the Columbus Fire

Division showed that “firefighter injuries occurred more often

when the total number of personnel on the fireground was less

than 15 at residential fires and 23 at large-risk fires” (Backoff

1980), and mounting evidence has indicated that staffing levels

are a fundamental health and safety issue for firefighters in

addition to being a key determinant of immediate response

capacity. One early analysis by the Seattle Fire Department for

that city’s Executive Board reviewed the average severity of

injuries suffered by three-, four-, and five-person engine

companies, with the finding that “the rate of firefighter injuries

expressed as total hours of disability per hours of fireground

exposure were 54 % greater for engine companies staffed with 3

personnel when compared to those staffed with 4 firefighters,

while companies staffed with 5 personnel had an injury rate that

was only one-third that associated with four-person companies”

(Cushman 1981). A joint report from the International

Association of Fire Fighters (IAFF) and Johns Hopkins University

concluded, after a comprehensive analysis of the minimum

staffing levels and firefighter injury rates in U.S. cities with

populations of 150,000 or more, that jurisdictions operating with

crews of less than four firefighters had injury rates nearly twice

the percentage of jurisdictions operating with crews of

four-person crews or more (IAFF, JHU 1991).

More recent studies have continued to support the finding that

staffing per piece of apparatus integrally affects the efficacy and

safety of fire department personnel during emergency response

and fire suppression. Two studies in particular demonstrate the

consistency of these conclusions and the increasing level of detail

and accuracy present in the most recent literature, by looking

closely at the discrete tasks that could be safely and effectively

performed by three- and four-person fire companies. After testing

drills comprised of a series of common fireground tasks at several

fire simulation sites, investigators from the Austin Fire

Department assessed the physiological impact and injury rates

among the variably staffed fire crews. In these simulations, an

increase from a three- to four-person crew resulted in marked

improvements in time-to-task completion or efficiency for the

two-story residential fire drill, aerial ladder evolution, and

high-rise fire drill, leading the researchers to conclude that loss of

life and property increases when a sufficient number of personnel

are not available to conduct the required tasks efficiently,

independent of firefighter experience, preparation, or training.

Reviews of injury reports by the Austin Fire Department

furthermore revealed that the injury rate for three-person

companies in the four years preceding the study was nearly

one-and-a-half that of crews staffed with four or more personnel

(Roberts 1993). In a sequence of similar tests, the Office of the

Fire Marshal of Ontario, Canada likewise found that three-person

Review of Literature

14
fire companies were unable to safely perform deployment of

backup protection lines, interior suppression or rescue operations,

ventilation operations that required access to the roof of the

involved structure, use of large hand-held hose lines, or establish a

water supply from a static source without additional assistance

and within the time limits of the study. Following these data, Fire

Marshal officials noted that three-person crews were also at

increased risk for exhaustion due to insufficient relief at fire

scenes and made recommendations for the minimum staffing

levels per apparatus necessary for suppression and rescue related

tasks (Office of the Fire Marshal of Ontario 1993).

The most comprehensive contemporary studies on the

implications of fire crew staffing now include much more

accurate performance measures for tasks at the fireground, in

addition to the basic metric of response time. They include

environmental measures of performance, such as total water

supply, which expand the potential for assessing the

cost-effectiveness of staffing not only in terms of fireground

personnel injury rates but also comparative resource expenditure

required for fire suppression. Several examples from the early

1990s show investigators and independent fire departments

beginning to gather the kind of specific, comprehensive data on

staffing and fireground tasks such as those suggested and outlined

in concurrent local government publications that dealt with

management of fire services (Coleman 1988). A report by the

Phoenix Fire Department laid out clear protocols for responding

to structure fires and response evaluation in terms of staffing,

objectives, task breakdowns, and times in addition to outlining

the responsibilities of responding fire department members and

the order in which they should be accomplished for a full-scale

simulation activity (Phoenix 1991). One attempt to devise a

prediction model for the effectiveness of manual fire suppression

similarly reached beyond response time benchmarks to describe

fire operations and the step-by-step actions of firefighters at

incident scenes by delineating the time-to-task breakdowns for

size-up, water supply, equipment selection, entry, locating the fire,

and advancing hose lines, while also comparing the predicted

time-to-task values with the actual times and total resources

(Menker 1994). Two separate studies of local fire department

performance, one from Taoyuan County in Taiwan and another

from the London Fire Brigade, have drawn ties between fire crews’

staffing levels and total water demand as the consequence of both

response time and fire severity. Field data from Taoyuan County

for cases of fire in commercial, business, hospital, and educational

properties showed that the type of land use as well as response

time had a significant impact on the water volume necessary for

fire suppression, with the notable quantitative finding that the

water supply required on-scene doubled when the fire department

response increased by ten minutes (Chang 2005).

Response time as a predictor of residential fire outcomes has

received less study than the effect of crew size. A Rand Institute

study demonstrated a relationship between the distance the

responding companies traveled and the physical property damage.

This study showed that the fire severity increased with response

distance, and therefore the magnitude of loss increased

proportionally (Rand 1978). Using records from 307 fires in

nonresidential buildings over a three-year period, investigators in

the United Kingdom correspondingly found response time to

have a significant impact on final fire area, which in turn was

proportional to total water demand (Sardqvist 2000).

Recent government and professional literature continues to

demonstrate the need for more data that would quantify in depth

and illustrate the required tasks, event sequences, and necessary

response times for effective fire suppression in order to determine

with accuracy the full effects of either a reduction or increase in

fire company staffing (Karter 2008). A report prepared for

National Institute of Standards and Technology (NIST) stressed

the ongoing need to elucidate the relationship between staffing

and personnel injury rates, stating that “a scientific study on the

relationship between the number of firefighters per engine and

the incidence of injuries would resolve a long-standing question

concerning staffing and safety” (TriData 2005). While not

addressing staffing levels as a central focus, an annual review of

fire department calls and false alarms by the National Fire

Protection Association (NFPA) exemplified the need to capture

not only the number of personnel per apparatus for effective fire

suppression but also to clarify the demands on individual fire

departments with resolution at the station level (NFPA 2008).

In light of the existing literature, there remain unanswered

questions about the relationships between fire service resource

deployment levels and associated risks. For the first time this

study investigates the effect of varying crew size, first apparatus

arrival time, and response time on firefighter safety, overall task

completion and interior residential tenability using realistic

residential fires. This study is also unique because of the array of

stakeholders and the caliber of technical advisors involved.

Additionally, the structure used in the field experiments included

customized instrumentation for the experiments; all related

industry standards were followed; robust research methods were

used; and the results and conclusions will directly inform the

NFPA 1710 Technical Committee, as well as public officials and

fire chiefs. 5

15

5 NFPA is a registered trademark of the National Fire Protection Association, Quincy, Massachusetts. NFPA 1710 defines minimum requirements relating to the

organization and deployment of fire suppression operations, emergency medical operations, and special operations to the public by substantially all career fire

departments. The requirements address functions and objectives of fire department emergency service delivery, response capabilities, and resources. The purpose of this

standard is to specify the minimum criteria addressing the effectiveness and efficiency of the career public fire suppression operations, emergency medical service, and

special operations delivery in protecting the citizens of the jurisdiction and the occupational safety and health of fire department employees. At the time of the

experiments, the 2004 edition of NFPA 1710 was the current edition.
This project systematically studies deployment of fire

fighting resources and the subsequent effect on both

firefighter safety and the ability to protect civilians and

their property. It is intended to enable fire departments and

city/county managers to make sound decisions regarding optimal

resource allocation to meet service commitments using the results

of scientifically based research. Specifically, the residential

fireground experiments provide quantitative data on the effect of

crew size, first-due engine arrival time, and subsequent apparatus

stagger on time-to-task for critical steps in response and fire

fighting.

The first phase of the multiphase project was an extensive survey

of more than 400 career and combination fire departments in the

United States with the objective of optimizing a fire service

leader’s capability to deploy resources to prevent or mitigate

adverse events that occur in risk- and hazard-filled environments.

The results of this survey are not documented in this report,

which is limited to the experimental phase of the project, but they

will constitute significant input into future applications of the

data presented in this document.

This report describes the second phase of the project, divided

into four parts:

 Part 1 — Laboratory experiments to design the appropriate

fuel packages to be used in the burn facility specially

constructed for the research project

 Part 2 — Field tests for critical time-to-task completion of key

tasks in fire suppression

 Part 3 — Field tests with real furniture (room and contents

experiments)

 Part 4 — Fire modeling to apply data gathered to slow-,

medium-, and fast-growth rate fires

The scope of this study is limited to understanding the relative

influence of deployment variables on low-hazard, residential

structure fires, similar in magnitude to the hazards described in

NFPA® 1710, Standard for the Organization and Deployment of

Fire Suppression Operations, Emergency Medical Operations, and

Special Operations to the Public by Career Fire Departments.

The standard uses as a typical residential structure a 2,000 sq ft

(186 m2) two-story, single-family dwelling with no basement and

no exposures (nearby buildings or hazards such as stacked

flammable material).

The limitations of the study, such as firefighters’ advance

knowledge of the facility constructed for this experiment,

invariable number of apparatus, and lack of experiments in

extreme temperatures or at night, will be discussed in the

Limitations section of this report. It should be noted that the

applicability of the conclusions from this report to commercial

structure fires, high-rise fires, outside fires, and response to

hazardous material incidents, acts of terrorism, and natural

disasters or other technical responses has not been assessed and

should not be extrapolated from this report.

Purpose and Scope of the Study

16
Regardless of the size of a structure on fire, firefighting

crews identify four priorities: life safety of occupants and

firefighters, confinement of the fire, property conservation,

and reduction of adverse environmental impact. Interdependent

and coordinated activities of all fire fighting personnel are

required to meet the priority objectives.

NFPA 1710 specifies that the number of on-duty fire

suppression personnel must be sufficient to carry out the

necessary fire fighting operations given the expected fire fighting

conditions. During each fireground experiment, the following

were dispatched to the test fire building:

 three engine companies

 one truck company

 a command vehicle with a battalion chief and a command

aide

Staffing numbers for the engine and truck crews and response

times were varied for the purposes of the tests. Additional

personnel available to ensure safety will be described later in this

report.

The following narrative account describes the general sequence

of activities in part 2 of the experiments (time-to-task), when the

fuel load permitted firefighter entry:

The first arriving engine company conducts a size-up or

initial life safety assessment of the building to include signs of

occupants in the home, construction features, and location of

the original fire and any extension to other parts of the

structure. This crew lays a supply line from a hydrant close to

the building for a continuous water supply.

The truck company usually arrives in close proximity to the

first engine company. The truck company is responsible for

gaining access or forcing entry into the building so that the

engine company can advance the first hose line into the

building to locate and extinguish the fire. Usually, they assist

the engine company in finding the fire. The NFPA and

OSHA 2 In/2 Out 6 crew is also assembled prior to anyone

entering an atmosphere that is immediately dangerous to life

or health (IDLH). This important safety requirement will

have a large impact on availability of firefighters to enter the

building when small crews are deployed.

Once a door is opened, the engine crew advances a hose line

(attack line) toward the location of the fire. At the same time,

members from the truck crew accompany the engine crew and

assist in ventilating the building to provide a more tenable

atmosphere for occupants and firefighters.Ventilation also

helps by improving visibility in an otherwise “pitch black”

environment, but it must be coordinated with the attack line

crew to ensure it helps control the fire and does not contribute

to fire growth. The truck crew performs a systematic rapid

search of the entire structure starting in the area where

occupants would be in the most danger. The most dangerous

area is proximate to the fire and the areas directly above

the fire.

Depending upon the travel distance, the battalion chief and

command aide will have arrived on the scene and have taken

command of the incident and established a command post.

The role of the incident commander is to develop the action

plan to mitigate the incident and see that those actions are

carried out in a safe, efficient, and effective manner. The

command aide is responsible for situational assessment and

communications, including communications with crew

officers to ensure personnel accountability.

Depending on response time or station location, the second

(engine 2) and possibly the third engine company (engine 3)

arrive. The second arriving engine (engine 2) connects to the

fire hydrant where the first engine (engine 1) laid their supply

line. Engine 2 pumps water from the hydrant through the

supply line to the first engine for fire fighting operations.

According to NFPA 1710, water should be flowing from the

supply line to the attack engine prior to the attack crew’s

entry into the structure.

The crew from the second engine advances a second hand

line as a backup line to protect firefighters operating on the

inside and to prevent fire from spreading to other parts of the

structure.

The third engine crew is responsible for establishing a Rapid

Intervention Team (RIT), a rescue team staged at or near the

command post or as designated by the Incident Commander

(in the front of the building) with all necessary equipment

needed to locate and/or rescue firefighters that become

trapped or incapacitated. The RIT plans entry/exit portals

and removes hazards, if found, to assist interior crews.

As the fire fighting, search and rescue, and ventilation

operations are continuing, two members of the truck

company are tasked with placing ground ladders to windows

and the roof to provide a means of egress for occupants or

firefighters. The truck crew is responsible for controlling

interior utilities such as gas and electric after their ventilation,

search, and rescue duties are completed.

Once the fire is located and extinguished and occupants are

A Brief Overview of the Fireground Operations

6 The “2 In/2 Out” policy is part of paragraph (g)(4) of OSHAs revised respiratory protection standard, 29 CFR 1910.134. This paragraph applies to private sector

workers engaged in interior structural fire fighting and to Federal employees covered under Section 19 of the Occupational Safety and Health Act. States that have chosen

to operate OSHA-approved occupational safety and health state plans are required to extend their jurisdiction to include employees of their state and local governments.

These states are required to adopt a standard at least as effective as the Federal standard within six months.

OSHAs interpretation on requirements for the number of workers required to be present when conducting operations in atmospheres that are immediately dangerous to

life and health (IDLH) covers the number of persons who must be on the scene before fire fighting personnel may initiate an attack on a structural fire. An interior

structural fire (an advanced fire that has spread inside of the building where high temperatures, “heat” and dense smoke are normally occurring) would present an IDLH

atmosphere and therefore, require the use of respirators. In those cases, at least two standby persons, in addition to the minimum of two persons inside needed to fight

the fire, must be present before fire fighters may enter the building.

Letter to Thomas N. Cooper, Purdue University, from Paula O. White, Director of Federal-State Operations, U.S. Department of Labor, Occupational Safety & Health

Administration, November 1, 1995.

17
removed, the incident commander reassesses the situation

and provides direction to conduct a very thorough secondary

search of the building to verify that the fire has not extended

into void spaces and that it is fully extinguished. (In a

nonexperimental fire situation, salvageable property would

be covered or removed to minimize damage.)

Throughout the entire incident, each crew officer is

responsible for the safety and accountability of his or her

personnel along with air management. The location and

wellness of crews is tracked by the command aide through a

system of personal accountability checks conducted at

20-minute intervals.

Following extinguishment of the fire, an onsite review is

conducted to identify actions for improvement. Crews are

monitored, hydrated and rested before returning to work in

the fire building.

The Relation of Time-to-Task Completion and Risk

Delayed response, particularly in conjunction with the

deployment of inadequate resources, reduces the likelihood of

controlling the fire in time to prevent major damage and possible

loss of life and increases the danger to firefighters.

Figure 1 illustrates a hypothetical sequence of events for

response to a structure fire. During fire growth, the temperature

of a typical compartment fire can rise to over 1,000o F (538o C).

When a fire in part of a compartment reaches flashover, the rapid

transition between the growth and the fully developed fire stage,

flame breaks out almost at once over the surface of all objects in

the compartment, with results for occupants, even firefighters in

full gear, that are frequently deadly.

Successful containment and control of a fire require the

coordination of many separate tasks. Fire suppression must be

coordinated with rescue operations, forcible entry, and utilities

control. Ventilation typically occurs only after an attack line is in

place and crews are ready to move in and attack the fire. The

incident commander needs up-to- the-minute knowledge of crew

activities and the status of task assignments which could result in

a decision to change from an offensive to a defensive strategy.

Standards of Response Cover

Developing a standard of response cover— the policies and

procedures that determine the distribution, concentration, and

reliability of fixed and mobile resources for response to fire (as

well as other kinds of technical response) — related to service

commitments to the community is a complex task. Fire and

rescue departments must evaluate existing (or proposed)

resources against identified risk levels in the community and

against the tasks necessary to conduct safe, efficient and effective

fire suppression at structures identified in these various risk levels.

Leaders must also evaluate geographic distribution and depth or

concentration of resources deployed based on time parameters.

Recognition and reporting of a fire sets off a chain of events

before firefighters arrive at the scene: call receipt and processing,

dispatch of resources, donning protective gear, and travel to the

scene. NFPA 1710 defines the overall time from dispatch to scene

arrival as the total response time. The standard divides total

Figure 1: Hypothetical Timeline of Fire Department Response to Structure Fire

18
response time into a number of discrete segments, of which travel

time — the time interval from the beginning of travel to the scene

to the arrival at the scene — is particularly important for this

study.

Arrival of a firefighting response force must be immediately

followed by organization of the resources into a logical, properly

phased sequence of tasks, some of which need to be performed

simultaneously. Knowing the time it takes to accomplish each

task with the allotted number of personnel and equipment is

critical. Ideally crews should arrive and intervene in sufficient

time to prevent flashover or spread beyond the room of origin.

Decision-making about staffing levels and geographic

distribution of resources must consider those times when there

will be simultaneous events requiring resource deployment.

There should be sufficient redundancy or overlap in the system to

allow for simultaneous calls and high volume of near

simultaneous responses without compromising the safety of the

public or firefighters.

Policy makers have long lacked studies that quantify changes in

fireground performance based on apparatus staffing levels and

on-scene arrival time intervals. These experiments were designed

to observe the impact of apparatus staffing levels and apparatus

arrival times on the time it takes to execute essential fireground

tasks and on the tenability inside the burn prop for a full initial

alarm assignment response. It is expected that the results of this

study will be used to evaluate the related performance objectives

in NFPA 1710.

19
Laboratory Experiments

The purpose of the first segment, the laboratory experiments, was

to characterize the burning behavior of the wood pallets as a

function of:

 number of pallets and the subsequent peak heat release rate

(HRR)

 compartment effects on burning of wood pallets

 effect of window ventilation on the fire

 effect on fire growth rate of the loading configuration of

excelsior (slender wood shavings typically used as packing

material)

Characterization of the fuel package was critical in order to

ensure that the field experiments would not result in a flashover

condition, one of the primary safety considerations in complying

with the protocols in NFPA 1403: Standard on Live fire Training

Evolutions.

7 Appendix A of this report contains the methods and

full results for the laboratory experiments, which are summarized

below. Figure 2 shows a test burn of pallets in the laboratory.

Results of Laboratory Experiments

The objective of the laboratory experiments was to quantify the

spread of heat and smoke throughout the planned burn prop in

order to ensure that the fuel package would result in a fire large

enough to generate heat and smoke consistent with a residential

structure fire, yet not so large as to transition to flashover. The

full results of the laboratory experiments and modeling are shown

in Appendix A and Appendix B. To summarize briefly, a

four-pallet configuration, which produced a peak of

approximately 2 MW, was determined to be the largest fuel load

the room could support without the threat of transitioning to

flashover. The compartment produced a negligible effect on the

heat release rate of the fire compared to open burning conditions.

The presence of an open window in the burn room reduced the

production of carbon monoxide and carbon dioxide gases,

primarily through enhanced oxygen availability and dilution,

respectively. The location and quantity of excelsior had a

significant impact on the growth rate of fire. More excelsior

located nearer the bottom of the pallets resulted in a more rapid

achievement of peak burning.

The results of the fuel load experiments to inform the building

and experimental design indicated development of untenable

conditions in the field experiments between 5 min and 15 min,

depending upon several factors: fire growth rate, ventilation

conditions, the total leakage of heat into the building and through

leakage paths, and manual fire suppression. This time frame

allowed for differentiation of the effectiveness of various fire

Part 1: Planning for the Field Experiments

Figure 2: Test Burn of Pallets in Laboratory

20

7 NFPA 1403 contains the minimum requirements for training all fire suppression peronnel engaged in firefighting operations under live fire conditions.
department response characteristics.

I

n part 2, fire experiments were conducted in a residential-scale

burn prop at the Montgomery County Public Safety Training

Academy in Rockville, MD.

Field Site

Montgomery County (MD) Fire and Rescue Department

provided an open space to construct a temporary burn prop, with

ready access to water and electrical utilities, at the Montgomery

County Fire and Rescue Training Facility in Rockville, MD.

The burn prop was constructed as a two-story duplex with a

common stairwell and movable walls between the sections to

allow for multiple experiments daily. Symmetrically dividing the

structure about the short axis allowed one side of the test

structure to cool and dry out after a fire test with suppression. The

burn prop contained two mirror-image, two-story units each

totaling 2,000 ft

2 (186 m2

), without basement or nearby exposures

— each therefore a typical model of a low-hazard single-family

residence identified in NFPA 1710. An exterior view of the burn

prop is shown in Figure 3. For each experiment there was a

confirmed fire in the living room in the first floor rear of one unit

of the structure.

Details and dimension are shown

in the floor plan in Figure 4.

The black lines in Figure 4

indicate load-bearing reinforced

concrete walls and red lines

indicate the gypsum over steel stud

partition walls. The ceiling height

was 94 in (2.4 m) throughout the

entire structure except in the burn

compartments,where additional

hardening was installed to protect

against repeated exposure to fire

during the experiments. This

additional fire proofing slightly

reduced the ceiling height.

Complete details about the

building construction are included

in Appendix C.

Noncombustible furniture (angle

iron and gypsum board

construction)wasfashioned to

represent obstacles of realistic size

and location forfirefighters

navigating the interior of the

structure. The dimensionswere

typical of residential furnishings.

Figure 5 shows an example of the

noncombustible furniture used in

the time-to-task experiments.

Part 2: Field Experiment Methods

Figure 3: Exterior View of Burn Prop

Figure 4: Dimensions of the Burn Prop Floor Plan

21
Overview of Field Experiments

In order to evaluate the performance representative of a NFPA

1710-compliant fire department, the field experiments consisted of

two parts (the second and third parts of the four described in this

report).In the first of the two parts of the field experiments,

firefighter participants from Montgomery County (MD) and Fairfax

County (VA) Fire Departments simulated an initial alarm assignment

response to a structure described in NFPA 1710 as a low-hazard

residential structure to which firefighters respond on a regular basis.

The staffing level of fire apparatus was varied incrementally from two

to five personnel per piece. The interval between apparatus on-scene

arrival times was varied at either 60 s or 120 s. Trained timing staff

were used to record the start and completion times of 22 tasks

deemed essential for mitigation of a residential fire incident by the

study’s technical experts. The pallet and excelsior configuration

chosen from the laboratory experiments repeatably produced a

consistent and realistic quantity of heat and smoke,similar to what

firefighters encounter at a residential structure fire.

Although the fire source used in part 2 of the field experiments

created a realistic amount of heat and smoke, the requirements of

NFPA 1403 prevented use of a fire source which could potentially

reach flashover within the structure. Therefore, part 3 of the fire

experiments was conducted in order to change the fuel package to

be representative of realistic fuel loading that could be found in a

living room in a residential structure (sleeper-sofa, upholstered

chairs, end tables, etc). The

intent of this part of the study

was to determine how the times

of firefighter interactions,

averaged with respect to the

staffing and arrival intervals,

impacted the interior tenability

conditions. Fire fighting tactics

were performed in a manner

which complied with NFPA

1403; ventilation was performed

with proper personal protective

equipment (PPE) and hand tools

from the exterior of the burn

prop. Suppression was

performed with an interior

remote suppression device

operated from the exterior of the

burn prop.

Instrumentation

Instrumentation to measure

gas temperature, gas

concentrations, heat flux, visual

obscuration, video, and time

during the experiments was

installed throughout the burn

prop. The data were recorded at

1-second intervals on a

computer-based data acquisition

system. Figure 6 presents a

schematic plan view of the

instrumentation. All

instruments were wired to a

centralized data collection room

attached as a separate space on

the west side of the building,

which is described later in this

report ensuring physical separation for the data collection

personnel from the effects of the fire, while minimizing the wire

and tube lengths to the data logging equipment. See Appendix C

for additional details about the instrumentation.

Figure 5: Noncombustible Furniture Used in the Time-to-Task Experiments

Figure 6: Instrumentation and Furniture Prop Layout

22
Safety Protocols

Firefighter safety was always a primary concern in conducting

the research. Participants were drawn from two departments —

Fairfax County,VA and Montgomery County, MD — that

regularly conduct NFPA 1403 compliant live fire training for their

staff and recruits.

A safety officer was assigned to the experiments by the

Montgomery County Fire and Rescue Department to assure

compliance with NFPA 1403. The safety officer (Figure 7)

participated in all orientation activities, daily briefings, and

firefighter gear checks and was always actively involved in

overseeing all experiments. The safety officer had full authority to

terminate any operation if any safety violation was observed. In

addition to the safety officer, a rapid intervention team (RIT),

assigned from dedicated crews not in the actual experiment, was

in place for each experiment, and a staffed ambulance was on

standby at the site. Radio communication was always available

during the experiments should a “mayday” emergency arise.

Experiments were stopped for any action considered to be a

protocol breach or safety concern. For example, all ladders — 24

ft (7.3 m) or 28 ft (8.5 m) — were to be raised by two firefighters.

As crew sizes were reduced, some firefighters attempted to place

ladders single-handedly in an effort to complete the task more

quickly. This procedure, while vividly illustrating how firefighters

try to do more with less in the field, is unsafe and could

potentially result in strain or impact injuries.

Additional safety features were built in to the field structure.

A deluge sprinkler system oriented to the known location of the

fuel package could be remotely activated for rapid fire

suppression. All first floor rooms had direct access to the exterior

of the building through either doors or windows. The second

story had an emergency exit to the roof of the attached

instrumentation room.

A closely related concern to ensure firefighter safety and

readiness to repeat experiments with equivalent performance was

adequate rehabilitation (see Figure 8). At the beginning and end

of each day, crews completed a health and safety check. The

importance of staying well-hydrated before and during

experiments was especially emphasized.

Figure 8: Crew Rehabilitation

Figure 7: Fireground Safety Officer

23
On-Scene Fire Department Tasks

The on-scene fire department task part of the study focused on

the tasks firefighters perform after they arrive on the scene of a

low-hazard residential structure fire. A number of nationally

recognized fire service experts were consulted during the

development of the on-scene fire department tasks in order to

ensure a broad applicability and appropriateness of the task

distribution.

8 The experiments compared crew performance and

workload for a typical fire fighting scenario using two-, three-,

four-, and five-person crews. 24 total experiments were conducted

to assess the time it took various crew sizes to complete the same

tasks on technically similar fires in the same structure. In addition

to crew sizes, the experiments assessed the effects of stagger

between the arriving companies. Close stagger was defined as a

1-minute time difference in the arrival of each responding

company. Far stagger was defined as a 2-minute time difference in

the arrival of each responding company. One-minute and

two-minute arrival stagger times were determined from analysis of

deployment data from more than 300 U.S. fire departments

responding to a survey of fire department operations conducted by

the International Association of Fire Chiefs (IAFC) and the

International Association of Fire Fighters (IAFF). Considering

both crew size and company stagger there were eight experiments

conducted in triplicate totaling twenty-four tests, as shown in the

full replicate block in Table 1. A full replicate was completed in a

randomized order (determined by randomization software) before

a test configuration was repeated.

Crew Size

For each experiment, three engines, a ladder-truck and a

battalion chief and an aide were dispatched to the scene of the

residential structure fire. The crew sizes studied included two-,

three-, four-, and five-person crews assigned to each engine and

truck dispatched. Resultant on-scene staffing totals for each

experiment follow: (FF = firefighter)

 Two Person crews = 8 FFs + Chief and Aide = 10 total on-scene

 Three Person crews = 12 FFs + Chief and Aide= 14 total

on-scene

 Four Person crews = 16 FFs + Chief and Aide = 18 total

on-scene

 Five Person crews = 20 FFs + Chief and Aide = 22 total

on-scene9

Department Participation

The experiments were conducted in Montgomery County, MD

at the Montgomery County Fire Rescue Training Academy during

the months of January and February 2009. All experiments took

place in daylight between 0800 hours and 1500 hours.

Experiments were postponed for heavy rain, ice, or snow and

rescheduled for a later date following other scheduled

experiments.

Montgomery County (MD) and Fairfax County (VA)

firefighters participated in the field experiments. Each day both

departments committed three engines, a ladder truck and

associated crews, as well as a battalion chief to the experiments.

The two battalion chiefs, alternated between the roles of battalion

chief and aide. Firefighters and officers were identified by

participating departments and oriented to the experiments. Each

experiment included engine crews, truck crews and command

officers from each participating department. Participants varied

with regard to age and experience. Crews that normally operated

together as a company were kept intact for the experiments to

assure typical operation for the crew during the scenarios.

However, in all experiments crews were used from both

departments, including engine crews, truck crews, and officers.

This allocation of resources made it possible to conduct

back-to-back experiments by rotating firefighters between field

work and rehabilitation areas.

Crew Orientation

All study participants were required to attend an orientation

prior to the beginning of the experiments (see Figure 9, page 25).

The orientations were used to explain experiment procedures,

task flows, division of labor between crews, and milestone events

in the scenario.

Daily orientations were conducted for all shifts to assure every

participant attended. Orientations included a description of the

overall study objectives as well as the actual experiments in which

they would be involved. Per the requirements of NFPA 1403, full

disclosure regarding the structure, the fire, and the tasks to be

completed were provided. Crews were also oriented to the

fireground props, instrumentation used for data collection, and

the specific scenarios to be conducted. Every crew member was

provided a walkthrough of the structure during the orientation

and each day prior to the start of the experiments.

Table 1: Primary Variables for Time-to-Task Experiments

8 Technical experts included Dennis Compton, Russell Sanders, William “Shorty” Bryson,Vincent Dunn, David Rohr, Richard Bowers, Michael Clemens, James Walsh,

Larry Jenkins and Doug Hinkle. More information about the experts is presented in the Acknowledgments later in this report.

9 Note that the on-scene totals account for only the personnel assigned to “work” the fire. Additional personnel were provided for an RIT team, a staffed ambulance on

site, and a safety officer specific to the experiments. The additional personnel are not included in thee staffing described above.

Time-to-Task Experiments

Crew Size Apparatus Stagger

2 Person Close Stagger (One minute)

3 Person Close Stagger (One minute)

4 Person Close Stagger (One minute)

5 Person Close Stagger (One minute)

2 Person Far Stagger (Two minutes)

3 Person Far Stagger (Two minutes)

4 Person Far Stagger (Two minutes)

5 Person Far Stagger (Two minutes)

24
Figure 10: Ground Ladders Figure 11: Ventilation

Figure 12: Ground Level Window Breakage Prop

Figure 14: Door Forcible Entry Prop Figure 15: Crew Preparation and Cue Cards

Figure 13: Second Story Window Breakage Prop

Figure 9: Crew Orientation and Walkthrough

25

Tasks

Twenty-two fireground tasks

were completed in each

experiment. Meticulous

procedures gathered data to

measure key areas of focus,

such as individual task start

times, task completion times,

and overall scenario

performance times. Each task

was assigned a standardized

start and end marker, such as

crossing the threshold to enter

the building with a hose line or

touching a ladder to raise it to

a second story window. The 22

tasks, with the events for

measuring start and stop times,

are shown in Table 2 (page26).

Figures 10 — 19 illustrate

firefighter activity in a number

of the tasks to complete

experiments or prepare for the

next experiment.

For reasons of both safety and

cost efficiency, two tasks —

forcible entry of the front door

and ventilation of the windows

on the first and second stories

— required special procedures.

The study could not

accommodate replacing the

doors and windows daily for

the fire suppression

experiments. Before the start

of experiments with the full

sequence of tasks, these two

tasks were measured in a

realistic manner using training

props constructed at the site of

the fireground experiments. As

with the overall experiments,

these two tasks were repeated in

triplicate and the times

averaged. The average time to

complete the tasks was then

used in the larger scale

experiment. As firefighters

came to the point of breaching

the door or windows, the timers

would hold them for the time

designated by the earlier

experiments and then give them

the approval to open the door

or windows. The start and end

times were then recorded just as

other tasks were.
Table 2: Tasks and Measurement Parameters

1. Stop at Hydrant, Wrap Hose START - Engine stopped at

hydrant

STOP - Firefighter back on engine

and wheels rolling

2. Position Engine 1 START - Wheels rolling from

hydrant

STOP - Wheels stopped at

structure

3. Conduct Size-up START - Officer off engine

(360-degree lap), transmit STOP - Completes radio

report, establish command transmission of report

4. Engage Pump START - Driver off engine

STOP - Driver throttles up pump

5. Position Attack Line START - Firefighter touches hose

(Forward Lay) to pull it from engine

STOP - Flake, charge and bleed

complete (hose at front door

prepared to advance)

6. Establish 2 In/2 Out Company officer announces – “2

In/2 Out established” (4 persons

assembled on scene OR at the

call of the Battalion

Chief/Company Officer)

7. Supply Attack Engine START - Firefighter touches

hydrant to attach line

STOP - Water supply to attack

engine

8. Establish RIT Time that Company Officer

announces RIT is established

9. Gain/Force Entry START - Action started

(HOLD time= 10 seconds)

STOP - Door opened for entry

10. Advance Attack Line START – Firefighter touches hose

STOP – Water on fire

11. Advance Backup Line START - Firefighter touches hose

(stop time at front door) to pull from engine bed

STOP - Backup line charged to

nozzle

12. Advance Backup START - Firefighter crosses

Line/Protect Stairwell threshold

STOP - Position line for attack at

stairwell

13. Conduct Primary Search START - Firefighters enter front

door

STOP - Firefighters transmit

“search complete”

14. Ground Ladders in Place START - Firefighter touches ladder

to pull it from truck

STOP - 4 Ladders thrown: 3

ladders on the 2nd

-story windows

and 1 to the roof

15. Horizontal Ventilation START- Firefighter at 1st window to

(Ground) begin ventilation (HOLD for 8

seconds)

STOP - Hold time complete -

window open

16. Horizontal Ventilation START - Firefighter grabs ladder

(2nd Story) for climb. (Firefighter must leg lock

for ventilation. HOLD time at each

window is 10 seconds)

STOP - All 2nd

-story windows open

- descend ladder - feet on ground.

17. Control Utilities (Interior) START - Radio transmission to

control utilities

STOP - When firefighter

completes the task at the prop

18. Control Utilities (Exterior) START - Radio transmission to

control utilities

STOP - When firefighter

completes the task at the prop

19. Conduct Secondary Search START - Firefighters enter front

door

STOP - Firefighters transmit

“secondary search complete”

20. Check for Fire Extension START- Firefighters pick up

(walls) check-for-extension prop

STOP- Completion of 4 sets total

(1 set = 4 in and 4 out)

This task may be done by more

than one person.

21. Check for Fire Extension START - Firefighters pick up

(ceilings) check-for-extension prop

STOP - Completion of 4 sets total

(1 set = 3 up and 5 down)

This task may be done by more

than one person.

22. Mechanical Ventilation START - Firefighters touch fans to

remove from truck

STOP - Fans in place at front door

and started

Tasks Measurement Parameters Tasks Measurement Parameters

26
Data Collection:

Standardized Control

Measures

Several control measures were

used to collect data, including

crew cue cards, radio

communications, task timers,

and video recording.

Performance was timed for each

task in each scenario including

selected milestone tasks such as

door breach, water-on-fire, and

individual window ventilation.

Data were collected for crew

performance on each task, and

individual firefighter

performance was not considered.

Task Flow Charts and

Crew Cue Cards

Task procedures were

standardized for each

experiment/scenario. Technical

experts worked with study

investigators to break down crew

tasks into individual tasks based

on crew size. Task flow charts

were created and then

customized for the various crew

sizes. The carefully designed task

flow ensured that the same

overall workload was maintained

in each experiment, but was

redistributed based on the

number of personnel available

for the work. See Appendix D

for additional details.

All tasks were included in each

scenario and cue cards were

developed for each individual

participant in each scenario. For

example, a four-person crew

would have a cue card for each

person on the crew including the

officer, the driver, and the two

firefighters. Cards were color

coded by crew size to assure

proper use in each scenario.

Radio communications

Interoperability of radio equipment used by both participating

departments made it possible to use regular duty radios for

communication during the experiments. Company officers were

instructed to use radios as they would in an actual incident.

Montgomery County Fire and Rescue Communications recorded

all radio interaction as a means of data backup. Once all data

quality control measure were complete, the records were then

overwritten as a routine procedure.

Task Timers

Ten observers/timers, trained in the use of a standard stop watch

with split-time feature, recorded time-to-task data for each field

experiment. To assure understanding of the observed tasks,

firefighters were used as timers, each assigned specific tasks to

observe and to record the start and end times.

To enhance accuracy and consistency in recording times, the data

recording sheets used several different colors for the tasks (see

Appendix D). Each timer was assigned tasks that were coded in the

same color as on the recording sheet. All timers wore high-visibility

safety gear on the fireground (see Figure 20).

Video records

In addition to the timers, video documentation provided a

backup for timed tasks and for quality control (see Figure 21). No

less than six cameras were used to record fireground activity from

varied vantage points. Observer/timer data were compared to

video records as part of the quality control process.

Figure 16: Connecting to the Hydrant Figure 17: Crews Responding

Figure 18: Ceiling Breach/Molitor Machine Figure 19: Incident Command

Figure 20: Task Timers Figure 21: Video Recording for Quality Control

27
Crew Assignment

Crews from each department that regularly operated together

were assigned to work as either engine or truck companies in each

scenario. Both Fairfax County and Montgomery County crews

participated in each experiment.

Crews assigned to each responding company position in one

scenario were assigned to another responding company position

in subsequent scenarios, with the objective of minimizing

learning from one experiment to another. For example, crews in

the role of engine 1 in a morning scenario might be assigned to

the engine 3 position in the afternoon, thus eliminating learning

from exact repetition of a task as a factor in time to completion.

Additionally, participating crews from both Montgomery County

and Fairfax County were from three different shifts, further

reducing opportunities for participant repetition in any one

position.

Response Time Assumptions

Response time assumptions were made based on time objectives

set forth in the NFPA 1710. Time stagger allocations were set by

the project technical advisors in order to assess the impact of

arriving unit time separation on task start and completion times,

as well as the overall scene time.

Below are the values assigned to the various time segments in

the overall response time. The total of the response time

segments may also be referred to as the total reflex time.

1. Fire ignition = time zero

2. 60 s for recognition (detection of fire) and call to 9-1-1

3. 60 s for call processing/dispatch

4. 60 s for turnout

10

5. Close Stagger = 240 s travel time FIRST engine with

60 s ladder-truck lag and 90 s lag for each subsequent engine

a. Truck arrives at 300 s from notification

b. Second engine at 330 s from notification

c. Third engine at 420 seconds from notification

6. Far Stagger = 240 s travel time FIRST engine with 120 s

ladder-truck lag and 150 s lag for each subsequent engine

a. Truck arrives at 360 s from notification

b. Second engine arrives at 390 s from notification

c. Third engine arrives at 540 s from notification.

The design of this part of the experiments allowed firefighter

entry into the burn building. The next part of the experiments

required a modified methodology.

28

10 After the experiments were complete, the NFPA 1710 technical committee released a new edition of the standard that prescribes 80 seconds for turnout time.
Part 3: Room and Contents Fires

As previously discussed,

NFPA 1403 prohibits

firefighters in a training

exercise from entering a

structure with sufficient fuel

load to result in room

flashover. But the value of the

data from the time-to-task

experiments lies not just in the

duration and

time-of-completion statistics

for tasks, but also in measuring

the tenability of the

atmosphere for occupants

urgently needing firefighter

assistance. Therefore Part 3 of

the experiments (room and

contents fires) used a larger

fuel load to focus on the seven

of the 22 tasks that cause a

change in the fire behavior

through ventilation or active suppression:

1. Forced entry of the front door

2. Water on fire

3. Second floor window #1 ventilated (burn room window)

4. Second floor window #2 ventilated (front window, near

corner)

5. Second floor window #3 ventilated (front window, near front

door)

6. First floor window #1 ventilated (window beside the fire

room)

7. First floor window #2 ventilated (self-ventilated at flashover)

Because the fuel load was sufficient for flashover, all firefighter

activity was conducted outside the building. Tasks that in Part 3

required entry into the building, such as search or interior utility

control, were factored into this part by delaying the next task for the

average duration of the task from Part 2. Firefighters in full gear

opened the door with a gloved hand or opened windows from the

ground with a tool such as a pike pole or angle iron, again at the

time specified by the averages from Part 2. Averages were derived

from the three iterations of each scenario. The different number of

iterations in Part 3 will be explained later in this report.

Because firefighters could not enter the building, a nozzle

controlled from the instrumentation room was installed. The

nozzle was placed in the room directly outside the burn room and

oriented toward the burn room near the doorway in order to best

emulate the nozzle location of live firefighter suppression (see

Figure 22). The nozzle was encased with mineral wool and

heavy-duty aluminum foil (bottom picture in Figure 22) to

protect the electronics and wiring from the intense radiation

energy emitted by the fire. Blocks were used to anchor the nozzle

against the lateral forces exerted by the momentum of the water

supply. The activation time for suppression was determined by

the data from the time-to-task test results.

A 15o spray pattern was directed toward the seat of the fire and

swept horizontally from side to side. While the remotely

controlled hose line knocked down the majority of the fire, it was

not as effective as a live firefighter with a better view into the

room of origin. Therefore, after the fire was diminished, a

supplemental stream was applied through the burn room window

in order to control the fire (see Figure 23). All personnel on the

hose line were in full turnout gear and self-contained breathing

apparatus during the exterior application of water.

Fuel Packages for the Room and Contents Fires

In order to maximize the repeatability of the fire development,

nominally identical rooms of furniture of identical manufacturer,

style, and age were used for each test. A plan-view schematic of

the furniture is shown in Figure 24 and pictures of the burn room

prior to testing are shown in Figure 25. Key dimensions, mass,

and materials for combustible furnishings are detailed in

Appendix C.

The Tornado Remote Controlled

Monitor is Produced by Task

Force Tips, Valparaiso, Indiana,

USA. Permission to publish

courtesy of Task Force Tips

Figure 23: Supplemental Suppression Applied for Room and

Contents Tests

Figure 22: Remotely Controlled Fire Suppression Nozzle for Room

and Contents Fires

29
T

heignitionsourceconsisted

ofacardboardbookof20

matchesthatwasignitedbyan

electricallyheatedwire,often

referredtoasanelectricmatch.

T

heelectricmatchwasplaced

nearthebottomofa21qt

(19.9L)polypropylenewaste

container.Theheightofthe

wastecontainerwas15.5in

(394mm)withinterior

dimensionsatthetopopening

of14.5in(368mm)by11.3in

(287mm).Approximately0.7

lbs(0.3kg)ofdrynewspaper

wasaddedtothewaste

container.Themajorityofthe

newspaperwasfoldedflat,and

placedonedgealongthesides

ofthewastecontainer.Four

sheetsofnewspaper,22in(559

mm)by25in(635mm)were

crumpledinto“balls”

approximately3.9in(100mm)

diameterandplacedontopof

theelectricmatchinthecenter

ofthewastecontainer.

ExperimentalMatrixfor

RoomandContentsFires

Sufficientamountsof

furniturefor16roomswere

availablefortheroomand

contentsfires,soeight

experimentscenerioswere

conducted—eachwitha

replicate.Becausethetimeto

untenableconditionswasa

primaryvariableofinterestin

theroomandcontentsfires,

thearrivaltimeofthefirstdue

enginewasaparamount

consideration.Becausethe

effectsofthesubsequent

apparatusstaggerwere

exploredinthetime-to-task

tests,thestaggerwasfixedat

the“closearrival”time.

Additionally,abaseline

measurementwasrequiredto

comparetheeffectivenessof

responsetotheabsenceofa

firedepartmentresponse.

Therefore,afive-person,later

arrivalcombinationwas

eliminatedinfavorofa

no-responsescenario(with

replicate).Table3summarizes

the16testsconducted.

Thefirstdueenginearrival

timesweredeterminedusing

thefollowingassumptions:

ignitionofthefireoccursat

Figure24:ConfigurationofFurnishingsinBurnRoom(RoomandContentsFires)

Figure25:PicturesoftheRoomandContentsFurnishings

30
time zero. Smoke detector

activation and a call to 9-1-1

occurs at 60 seconds after the

fire starts. Call intake and

processing requires an

additional 90 seconds. The

firefighters take 60 seconds to

complete their turnout at the

station and begin travel to the

scene. Thus travel time begins

3.5 minutes into experiment.

The two levels of arrival time

are then determined by two

different travel times: early

arrival assumes a three-minute

travel time, while later arrival

assumes a five-minute travel

time. For all scenarios in the

room and contents experiments,

the close stagger (60 seconds)

between subsequent apparatus

times was used.

Procedure for Minimizing the Effect of Variance in Fire

Growth Rate

Fires involving furnishings have inherent variance in burning

behaviors. Factors such as humidity and minor variations in

materials (particularly worn furnishings that may have different

foam compression or fabric wear patterns), can result in

uncertainty of 20 % or more, despite significant efforts to

enhance repeatability. The early growth period of fire

development is often associated with the greatest variance, since

minor factors (as discussed above) can influence the thermal

environment more easily when the fire is small. Therefore, the

room and contents fires were normalized to the 212 °F (100 °C)

temperature near the ceiling in the burn room in order to

minimize the variance of the room and contents fires. The time at

which the burn room reached this temperature (usually in

approximately 180 seconds) rather than the actual ignition time,

was designated as the “zero time.”

Figure 26 shows the time-temperature curves before and after

normalizing at 100°C. This approach was implemented during the

experiments by watching the time temperature data in real-time

from the instrumentation room and announcing the “zero-time”

over the fireground radio system. The normalization procedure

did not negatively affect tenability measurements in the target

room because when the fire is small, products of combustion do

not reach the room because of lack of momentum. Therefore,

adjusting all room and contents tests to the same upper layer

temperature was an appropriate way to minimize variance.

Milestone Times for Critical Tasks

As stated earlier, firefighters could not enterthe burn building during

the room and contents experiments because of the danger for

potential flashover in an experimental scenario. Therefore,

prescribed tasks were performed at specified times based on data from

part 2. In this section we report on significant data gathered from

instrumentation and describe an additional part of the experiments

designed to extend our understanding of the effect of crew size and

stagger on the tenability of the atmosphere in a burning structure.

Table 4 (page 32) identifies significant tasks selected as key

milestones because of the way they affect fire behavior and

atmospheric tenability inside the structure.

Crew Size First Due Arrival Time

2-Person Early Arrival of First Engine (6.5 min) – close stagger

3-Person Early Arrival of First Engine (6.5 min) – close stagger

4-Person Early Arrival of First Engine (6.5 min) – close stagger

5-Person Early Arrival of First Engine (6.5 min) – close stagger

2-Person Later Arrival of First Engine (8.5 min) – close stagger

3-Person Later Arrival of First Engine (8.5 min) – close stagger

4-Person Later Arrival of First Engine (8.5 min) – close stagger

No Response (Baseline) N/A

Table 3: Experimental Matrix for Room and Contents Tests (Each Conducted in Replicate)

Figure 26: Direct Comparison of Temperatures,

Before (Top) and After Adjustment (Bottom)

31
Table 4: Tasks That Affect Fire Behavior and Atmospheric Tenability

32
This section describes the analytic approaches used to

address the research objectives of the study. First the

statistical methods used to analyze the fireground

time-to-task observations are presented. Then the time-to-task

data and the room and contents data were combined to assess

crew performance in relation to tenability within the structure.

Time-to-Task Analysis

Time-to-task data were compiled into a database and assessed

for outliers and missing entries. Because all time-to-task

experiments were conducted in triplicate, missing data were

apparent and were reviewed via video and radio tapes. Missing

data attributable to timer error were replaced by a time observed

in the video. Where video and/or radio documentation was not

adequate, missing data were recoded to the mean of the task times

from the other two experiments.

Data Queries

The statistical methods used to analyze the time-to-task data

were driven by a principal goal of this research project — to assess

the effect of crew size, first-due engine arrival time, and

subsequent apparatus stagger on time-to-task for critical steps in

response and fire fighting. This research goal motivated the

development of four specific research questions (see Figure 27)

that in turn pointed to specific statistical analyses for generating

inference and insight.

Statistical Methods – Time-to-Task

The analysis of the time-to-task data involved a sequence of

multiple linear regressions using Ordinary Least Squares to

generate and test the effects of staffing and stagger on timings.

The regressions were of the form:

where the xik reflect factors such as stagger and crew size, and the

y represents our dependent/outcome variable.

Time-related outcomes (i.e., the dependent variables in the

regression equations) could include task duration, elapsed time to

start the task, and elapsed time until task completion, all

measured in seconds. Table 5 (page 34) lists the time-related

outcomes used to test the effect of crew size and stagger for the

tasks in the field experiments.

The effects of crew size and stagger were explored using

indicator variables in the regression analyses. The coefficient for a

given indicator (for example, crew size of four relative to a crew

size of two) indicated the number of seconds the larger crew size

added or reduce the timing outcome of a task. Crew sizes were

collapsed in some regressions to test whether the timings of

“larger” crew sizes of four and five were significantly different

than “smaller” crew sizes of two and three. Interaction terms were

not assessed in these regression analyses because of the small

number of experiments available for analysis.

Standard t-tests examined statistical significance (i.e., to see if

the hypothesis of “no impact” could be rejected) to estimate the

impact of several specific configurations:

 crew sizes of three versus two

 crew sizes of four versus three

 crew sizes of five versus four

 (occasionally) five versus two, and four versus two

 larger (four & five combined) versus smaller (two & three

combined) and

 stagger

The specific tests for each task (regression analysis) are shown in

the Appendix E. The actual coefficients of each regression and

their corresponding standard errors are presented in Appendix F.

To infer impact, significant tests were conducted at the 0.05

significance level. Only statistically significant contrasts of crew

size and/or stagger are included in this section of the report.

Graphic expositions of relevant time/task related findings are then

presented as well. Where stagger was statistically significant, the

effects are graphed separately. Where stagger was not statistically

significant, the data for crew size were combined.

Analysis of Experimental Results

Time-to-Task Research Questions

1) How do crew size and stagger (i.e., timing of between first

engine and subsequent apparatuses) affect overall (i.e.,

start to completion) response timing?

a. To what extent do variations in crew size affect overall

response timing?

b. To what extent do variations in both crew size and

stagger affect overall response timing?

2) How do crew size and stagger affect the timings of task

initiation, task duration, and task completion for each of

the tasks comprising the suite of 22 tasks?

a. To what extent do variations in crew size affect timings

across the suite of tasks?

b. To what extent do variations in both crew size and

stagger affect response timings across the suite of

tasks?

3) How does crew size affect elapsed times to achieve three

critical events known to change fire behavior or

atmospheric tenability for occupants?

a. Entry into structure

b. Water on fire

c. Ventilation of each window (three upstairs and one

downstairs window and the burn room window)

4) How does the elapsed time to achieve the national

standard of assembling 15 firefighters at the scene

(measured using “at hydrant” as the start time) vary by

crew sizes of 4 and 5?

Figure 27: Research Questions for Time-to-Task Experiments

33
Regression analyses

Appendix F presents the

regression results for each task

and relevant outcome, along

with their corresponding

standard errors. The results of

conducting significance tests at

the 0.05 level of significance

are shown in Appendix E.

Rather than detailing each of

the lengthy lists of coefficients

found to be significant, only

the answers to the primary

research questions are

presented for each task.

Measurement Uncertainty

The measurements of length,

temperature, mass, moisture

content, smoke obscuration,

and stopwatch timing taken in

these experiments have unique

components of uncertainty that

must be evaluated in order to

determine the fidelity of the

data. Appendix G summarizes

the uncertainty of key

measurements taken during the

experiments. Importantly, the

magnitudes of uncertainties

associated with these

measurements have no impact

on the statistical inferences

presented in this report.

How to Interpret

Time-to-Task Graphs

Figure 28 presents a sample

time-to-task analysis, in this

case results for venting time.

Each crew size has a column

graphic showing the start time

and completion time for the

task. Visually, columns starting

lower on the graph depict

deployment configurations

that resulted in earlier start

times. The height of the

column graphic is a

visualization of the duration of

the task, taller columns

indicating longer times to task

completion. Time data are also

shown in a table below the

graph. Where stagger was

statistically significant, the

effects are graphed separately.

Where stagger was not

statistically significant, as in the

illustration, the data for crew

size were combined.

Table 5: Dependent Variables Used in a Regression Analysis of the Effect of Crew Size and Stagger on

Time-to-Task Outcomes

Figure 28: Example Time-to-Task Graph

34
Time-to-Task Graphs

Overall Scene Time (Time to

Complete All 22 Tasks)

The four-person crews

operating on a low-hazard

structure fire completed the

same number of tasks on the

fireground (on average) 7

minutes faster than the

two-person crews (see Figure

29). The four-person crews

completed the same number of

fireground tasks (on average)

5.1 minutes faster than the

three-person crew. The

four-person crews were able to

complete necessary fireground

tasks on a low-hazard

residential structure fire nearly

30 % faster than the

two-person crews and nearly

25 % faster than the

three-person crews. Although

on the low-hazard residential

structure fire, adding a fifth

person to the crews did not

show any additional decrease in

fireground task times, the

benefits of a five-person vs. a

four-person crew are significant

in other measurements,

particularly the “water-on-fire”

time. Additionally, the greater

need for five-person crews for

medium- and high-hazard

structures, particularly in urban

settings, has been documented

in other studies (Backoff et al.,

1980; Cushman, 1982;

McManis Associates et al.,

1984) and five-person crews are

required for areas that contain

medium and high-hazard

structures in fire protection

consensus standards.

11

Figure 29: Overall Scene Time

11 NFPA 1710, Section 5.2.3.1.2 and Section 5.2.3.2.2: In jurisdictions with tactical hazards, high-hazard occupancies, high incident frequencies, geographical

restrictions, or other pertinent factors as identified by the AHJ, these companies shall be staffed with a minimum of five or six on duty members.

35
Figure 30 b: Overall Scene Time-Four Person Crew

Overall Scene Time and

Crew Sizes

The graphs in Figure 30 show

average times for each task by

crew size.

Figure 30 a: Overall Scene Time-FIve Person Crew

36
Figure 30 c: Overall Scene Time-Three Person Crew

Figure 30 d: Overall Scene Time-Two Person Crew

37
38

Advance Attack Line

Time (Hose Stretch Time)

Figure 31 measures the

interval from the start of the

task “Position Attack Line” to

the end of the task “Advance

Attack Line.” In comparing

four- and five-person crews to

two and three-person crews

collectively, the time difference

for this measure was

statistically significant at 76

seconds (1 minute 16 seconds).

In conducting more specific

analysis comparing all crew

sizes to a two-person crew the

differences are more distinct. A

two-person crew took 57

seconds longer than a

three-person crew to stretch a

line. A two-person crew took

87 seconds longer than a

four-person crew to complete

the same task. Finally, the most

notable comparison was

between a two-person crew and

a five-person crew, with a

122-second difference in task

completion time.

12, 13 Figure 31: Advance Line Time (Hose Stretch Time) by Crew Size

12 Apparatus stagger was not statistically significant, so the data for crew size were combined.

13 Where subtracting the start time from the end time yields a result that differs from the duration noted in the chart by one second, it is the result of rounding fractional

seconds to the nearest whole second.
39

Time to Water on Fire

There was a 10% difference in

the “water on fire” time

between the two- and

three-person crews. There was

an additional 6% difference in

the "water on fire" time

between the three- and

four-person crews. (i.e.,

four-person crews put water on

the fire 16% faster than two

person crews). There was an

additional 6% difference in the

“water on fire” time between

the four- and five-person crews

(i.e. five-person crews put

water on the fire 22% faster

than two-person crews).

Advancing a Backup Line

Advancing a backup line to

the door and stairwell was

started 16 % faster and

completed 9 % for replicates

with shorter staggers between

company arrivals. Advancing a

backup line is typically a task

completed by the third arriving

engine on a full alarm

assignment and is critical to

the safety of firefighters already

in the building on the initial

attack line. For this task,

stagger of arrival was

statistically significant and is

an important consideration for

overall station location and full

alarm response capability. The

differences can be seen in

Figure 33, which shows the

time from the start for the task

“Deploy Backup Line” to the

end of the task “Advance

Backup Line.”

Figure 32: Water on Fire Time by Crew Size and Stagger

Figure 33: Times to Advance Backup Line by Crew Size and Stagger
14 Stagger was not significant, so data from close and far were combined to increase statistical power.

40

Figure 34: Times to Conduct Primary Search by Crew Size
Primary Search

Figure 34 summarizes the

times that crews took to start

the primary search. On the

low-hazard, two-story

single-family dwelling 2,000 sq

ft (186 m2) , the three-person

crew started a primary

search/rescue more than 25 %

faster than the two-person

crew. In the same structure,

the four- and five-person crews

started a primary search 6 %

faster than the three-person

crews and 30 % faster than the

two-person crew. Note that

there is no end time included

in this figure. Primary search

end times were reliant upon

radio communication by

firefighters inside the structure.

On occasion this

communication did not occur

or was delayed. Therefore data

reliability was insufficient for

analysis of task duration and

end time.

14

Laddering and

Venting Time

A four-person crew operating

on a low-hazard structure fire

completed laddering and

ventilation (for life safety and

rescue) 30 % faster than a

two-person crew and 25 %

faster than a three-person crew.

Ground laddering time

started with the removal of the

first ladder from the truck and

stopped at end time of the last

ladder put in place. A total of

four ladders were raised on

each experiment.

Truck operations ventilation

time is the time from the start

time of ventilation of the first

window until the last window

ventilation was complete.

The differences in start times

and duration of the tasks can be

seen in Figure 35 and Figure 36.

Figure 35: Laddering Time by Crew Size

Figure 36: Ventilation Times by Crew Size15

15 Stagger was not statistically significant, so the data for crew size were combined.

41
42

16 Stagger was not statistically significant, so the data for far and near stagger were combined.

Figure 37: Industry Standard Effective Response Force Assembly Time

Industry Standard

Effective Response Force

Assembly Time

NFPA 1710 requires that a fire

department have the capability

to deploy an initial full-alarm

assignment to a scene within

eight-minutes (480 seconds).

The number of people required

falls between 15 and 17,

depending on whether an

aerial apparatus is used, and/or

if two engines are being used to

provide a continuous water

supply. In these experiments,

the measurement for an

effective response force

assembly time started from the

first engine arrival at the

hydrant and ended when 15

firefighters were assembled on

scene. Figure 37 reveals the

differences in assembly times

between the four and

five-person crews. An effective

response force was assembled

by the five-person crews a full

three minutes faster than the

four-person crews. It is

important to note that (by

definition), the two-and

three-person crews were unable

to meet this standard at any

time during the experiments.

16
43

Part 4: Fire Modeling

I

n the room and contents

experiments conducted in

Part 3 of the study,

instrumentation measured

oxygen, carbon dioxide, and

carbon monoxide

concentrations. Data were

grouped by the type of

experiment conducted with

respect to crew size and first

due engine arrival time. As

previously shown in the

experimental matrix, each

group contained two replicate

tests. In each group of data the

results of the replicates were

averaged to simplify the data

for further comparison. Figure

38 and Figure 39 show the

typical concentration curves for

the experiments.

These two graphs show the

ranges representative of those

found in the experiments.

Charts of gas curves for the

remainder of the experiments

— for both the burn room and

the target room — can be

found in Appendix H.

Fire Modeling Methods

A primary goal of fire

department response is to

prevent civilian injuries and

deaths. Because the significant

majority of fire deaths in the

United States occur in

residences, a rapid fire service

response provides the last

line-of-defense against civilian

fire deaths. Further, because the

fire service is less likely to rescue

occupants intimate with the

fire (i.e., inside the room of

origin where conditions

deteriorate rapidly), tenability

measurements were taken in a

remote bedroom on the second

floor of the residential burn

structure. The gas and

temperature measurements were

taken at the 5 ft (1.5 m ) height

above the floor, 3 ft (0.9 m)

from the west wall in order to

simulate a nonambulatory

occupant (e.g,someone asleep,

under the influence of alcohol or

drugs, or otherwise mobility

impaired).

Figure 38: Representative Oxygen Concentration

Figure 39: Representative Carbon Monoxide and Carbon Dioxide Concentrations
Computational fire models used the average suppression timings

obtained from the time-to-task experiments under specific

deployment configurations as inputs to the model. This

quantitative approach eliminated the experimental variance of the

fire. The resulting “computational” fire is repeatable, and

therefore, any differences in occupant exposure to toxic gases will

be due to the intervention times associated with a specific

deployment configuration rather than the random variation that

naturally occurs from fire to fire.

Fire simulations were completed using the NIST Fire Dynamics

Simulator (FDS). FDS is a computational fluid dynamics model of

fire-driven fluid flow. The first version of the FDS was released in

2000. FDS has been extensively verified and validated (USNRC

2007). Since the initial release, numerous improvements have

been made and new features added. This study used FDS version

5.4.2 (Sub-version #4957), which was released on October 19,

2009. In order to calibrate the model, simulations were

performed to replicate the experimental results observed in the

Figure 40: Measured vs. Predicted Temperature at the 2.1 m (6.9 ft)

Thermocouple Location in the Burn Compartment

Figure 41: Measured vs. Predicted Temperature at the 1.8 m (5.9 ft)

Thermocouple Location in the Burn Compartment

Figure 42: Measured vs. Predicted Temperature at the 1.5 m (4.9 ft)

Thermocouple Location in the Burn Compartment

Figure 43: Measured vs. Predicted Temperature at the 1.2 m (3.9 ft)

Thermocouple Location in the Burn Compartment

Figure 44: Measured vs. Predicted Temperature at the 0.9 m (2.9 ft)

Thermocouple Location in the Burn Compartment

Figure 45: Measured vs. Predicted Temperature at the 0.6 m (1.9 ft)

Thermocouple Location in the Burn Compartment

44
room-and-contents fires. Once

the ability of the model to

replicate experimental results was

established, the different fire

growth rates and deployment

configurations were simulated to

characterize the effectiveness of

different responses relative to

different fire growth rates.

The occupant exposure to toxic

gases was assumed to occur until

the occupant is rescued by the

truck crew (start time of primary

search plus one minute). Table 6

shows the “rescue time” for the

various crew sizes that correspond

to the test matrix for the room

and contents experiments.

Part 4 of the experiments used

fire modeling to correlate response

times to atmospheric tenability in

a burning structure. In order to

calibrate the computer fire model,

simulations were performed to

replicate the experimental

results observed in the

room-and-contents fires.

Model inputs include building

geometry and material properties, ventilation paths (doors,

windows, leakage paths), and heat release rate of the fuel package.

While the building geometry is easily measured and material

properties (such as the thermal properties of drywall and

concrete) are readily estimated, the heat release rate was not

directly measured during the experiments. The heat release rate

of the fuel package is the primary determinant of the production

rate of heat, smoke, and gas species (e.g., carbon dioxide, carbon

monoxide).

Figures 40 through 45 compare the experimental and simulated

burn room temperatures using the burn room thermocouple tree.

The tree contained thermocouples located at 0.6 m (1.9 ft),

0.9 m (2.9 ft), 1.2 m (3.9 ft), 1.5 m (4.9 ft), 1.8 m (5.9 ft), and

2.1 m (6.9 ft) above the floor. For additional information about

the instrumentation type location, see Appendix C. The results

for thermocouples located in the hot gas layer show excellent

agreement. The temperature at the lower two thermocouples

show an overprediction of the hot gas layer depth in the computer

simulation. A small difference in the location of the interface

height (the steep temperature gradient between the relatively cool

lower gas layer and the hot upper gas layer), can result in

significant predicted temperature differences with relatively little

effect on the bulk heat and mass transport accuracy. This

explanation is supported by the agreement of the temperatures in

the remote bedroom.

Figure 46 compares the experimental and predicted oxygen

concentration levels in the upstairs bedroom (measured at 5 ft

(1.5 m) above the floor, centered above the bed). Figures 47

through 52 compare the experimental and simulated

temperatures in the upstairs (target room) bedroom. As expected,

the temperatures are moderated by mixing (cool ambient air

mixes with hot combustion gases during transport between the

burn room and the target room) and by thermal losses to the

(cooler) surfaces between the two rooms.

Once the model inputs were determined to agree with the

experimental results, the input heat release rate was changed to

represent three fire growth rates representative of a range of fire

hazard development – slow, medium, and fast, which are

described in greater detail in the following sections.

Time to Untenable Conditions: Research Questions

In the real world, fires grow at many different rates – from very

slow, smoldering fires all the way to ultra-fast, liquid fuel or spray

fires. In order to extend the applicability of the findings of this

report beyond the one fire growth rate observed in part 3 of this

report (residential room and contents fires), computer fire

modeling was used to quantify the effectiveness of fire

department operations in response to an idealized range of fire

growth rates (characterized as slow, medium, and fast). Based on

the research questions shown in Figure 53, fire modeling methods

were then selected to maximize the applicability of the times to

task results.

Figure 46: Measured Versus Predicted Oxygen Levels in the Upstairs Bedroom at 5 ft (1.5 m)

1) How do performance times relate to fire growth as

projected by standard fire time/temperature curves?

2) How do these performance times vary by crew size,

first due arrival time, and stagger?

3) How do crew size, stagger, and arrival time affect

occupant tenability within the structure?

Figure 53: Research Questions for Time to Untenable Conditions

45
Figure 47: Measured vs. Predicted Temperature at the 2.4 m (7.8 ft)

Thermocouple Location in the Bedroom

Figure 48: Measured vs. Predicted Temperature at the 2.1 m (6.8 ft)

Thermocouple Location in the Bedroom

Figure 49: Measured vs. Predicted Temperature at the 1.8 m (5.9 ft)

Thermocouple Location in the Bedroom

Figure 50: Measured vs. Predicted Temperature at the 1.5 m (4.9 ft)

Thermocouple Location in the Bedroom

Figure 51: Measured vs. Predicted Temperature at the 1.2 m (3.9 ft)

Thermocouple Location in the Bedroom

Figure 52: Measured vs. Predicted Temperature at the 0.9 m (2.9 ft)

Thermocouple Location in the Bedroom

Fire Growth Rates

Three fire growth rates were used in the computer fire modeling to

assess the effectiveness of different fire department deployment

configurations in response to fires that were similar to, faster growing,

and slower growing than the fires observed in the room-and-contents

fires. The slow, medium, and fast fire growth rates are defined by the

Society of Fire Protection Engineers according to the time at which

they reach 1 megawatt (MW). A typical upholstered chair burning at

its peak would produce a 1-MW fire,while a large sofa at its burning

peak would produce roughly a 2-MW fire.

The growth rate of fires is often approximated by simple

correlation of heat release rate to the square of time. If a fire is not

suppressed before full-room involvement, the probability of

spread beyond the room of origin increases dramatically if there is

nearby fuel load to support fire spread. If a nearby fuel load is

available, the 12 ft (3.7 m) by 16 ft (4.9 m) compartment used in

the fire experiments would become fully involved at

approximately 2 MW. Table 7 shows the time in seconds at which

1-MW and 2-MW (fully involved) fires in this compartment

would be reached in the absence of suppression.

46
A fire department rescue

operation is a race between the

deteriorating interior conditions

inside the structure and the

rescue and suppression activities

of the fire department. Each fire

growth rate was used as a

baseline heat release rate for the

simulation. Intervention times

(window and door opening times

and suppression time) from the time-to-task tests were

systematically input into the model to evaluate the effects on

interior tenability conditions. The interior tenability conditions

were calculated in a remote upstairs bedroom (above the room of

fire origin on the first floor) in order to maximize the opportunity

for differentiation among different crew configurations.

Fractional Effective Dose (FED)

In order to convert instantaneous measurements of local gas

conditions, the fractional effective dose (FED) formulation published

by the International Standards Organization (ISO) in document

13571 Life-threatening Components of Fire – Guidelines for the

Estimation of Time Availablefor Escape Using Fire Data (ISO 2007)

were used. FED is a probabilistic estimate of the effects of toxic gases

on humans exposed to fire effluent. The formulation used in the

simulations accounts for carbon monoxide (CO), carbon dioxide

(CO2), and oxygen (O2) depletion. Other gases, including hydrogen

cyanide (HCN) and hydrogen chloride (HCl),were not accounted

for in this analysis and may alter FED for an actual occupant.

There are three FED thresholds generally representative of

different exposure sensitivities of the general population. An FED

value of 0.3 indicates the potential for certain sensitive

populations to become incapacitated as a result of exposure to

toxic combustion products. Sensitive populations may include

elderly, young, or individuals with compromised immune

systems. Incapacitation is the point at which occupants can no

longer effect their own escape. An FED value of 1.0 represents the

median incapacitating exposure. In other words, 50 % of the

general population will be incapacitated at that exposure level.

Finally, an FED value of 3.0 represents the value where occupants

who are particularly tolerant of combustion gas exposure

(extremely fit persons, for example) are likely to become

incapacitated.

These thresholds are statistical probabilities, not exact

measurements. There is variability in the way individuals respond

to toxic atmospheric conditions. FED values above 2.0 are often

fatal doses for so-called typical occupants. There is no threshold

so low that it can be said to be safe for every exposed occupant.

17

2-Person Early 12:47

3-Person Early 9:03

4-Person Early 9:10

5-Person Early 8:57

2-Person Late 14:47

3-Person Late 11:03

4-Person Late 11:10

Table 6: Rescue Time for Different Deployment Configurations

Deployment

Configuration

(All times with

close stagger adjusted

for early and late arrival

of first due engine)

Rescue Time for

Deployment

Configuration

(Min : Sec)

Fire Growth Rate Time in Seconds Time in Seconds to

Reach 1 MW Reach to 2 MW

Slow 600 848

Medium 300 424

Fast 150 212

Table 7: Time to Reach 1 MW and 2 MW by Fire Growth Rate In the Absence of Suppression

Where Ci is the concentration of the ith gas and (Ct)i is

the toxic concentration of ith gas and Δt is the time increment.

Eq.1

47

17 See the following sections of ISO Document 13571:

5.2 Given the scope of this Technical Specification, FED and/or FEC values of 1,0 are associated, by definition, with sublethal effects that would render occupants of

average susceptibility incapable of effecting their own escape. The variability of human responses to toxicological insults is best represented by a distribution that takes

into account varying susceptibility to the insult. Some people are more sensitive than the average, while others may be more resistant (see Annex A.1.5). The traditional

approach in toxicology is to employ a safety factor to take into consideration the variability among humans, serving to protect the more susceptible subpopulations.

5.2.1 As an example, within the context of reasonable fire scenarios FED and/or FEC threshold criteria of 0,3 could be used for most general occupancies in order to

provide for escape by the more sensitive subpopulations. However, the user of this Technical Specification has the flexibility to choose other FED and/or FEC threshold

criteria as may be appropriate for chosen fire safety objectives. More conservative FED and/or FEC threshold criteria may be employed for those occupancies that are

intended for use by especially susceptible subpopulations. By whatever rationale FED and FEC threshold criteria are chosen, a single value for both FED and FEC must be

used in a given calculation of the time available for escape.
Results from Modeling Methods

Table 8 shows the FED for slow-, medium-, and fast-growth rate

fires correlated to rescue times based on crew size and arrival time

in the study. As with the room-and-contents fire in part 3, results

in Table 8 included only the close-stagger rescue time data. The

effect of far-stagger rescue times on occupant tenability should be

investigated in future studies. Values above 0.3 are shown in

yellow, and those above the median incapacitating exposure of 1.0

are shown in red.

Figure 54 shows that with slow-growth fires in the experimental

residential structure, all crew configurations could achieve rescue

time before FED reached incapacitating levels. Figure 55

illustrates the greater danger of

medium-growth fires, where

the FED at rescue time for

two-person crews is well above

the 0.3 level, and almost to that

level for the other crews.

Figure 56 (page 49) vividly

illustrates the extreme danger

of fast-growth fires. By the

time a two-person crew is able

to facilitate a rescue, the FED

has far exceeded the median

1.0 level. For other crew sizes,

the FED has exceeded 0.3,

which is a threshold level for

vulnerable populations.

Table 8: FED as a Function of Deployment Configuration and Fire Growth Rate

Figure 54: FED Curves for Early Arrival for All Crew Sizes at

Slow-Growth Fires

Remote Room Tenability for Slow Fires

Figure 55: Average FED Curves for Early Arrival for All Crew Sizes

at Medium-Growth Fires

Remote Room Tenability for Medium Fires

48

results
Interior Firefighting Conditions and Deployment

Configuration

The available time to control a fire can be quite small. Risks to

firefighters are lower for smaller fires than larger fires because

smaller fires are easier to suppress and produce less heat and fewer

toxic gases. Therefore, firefighter deployment configurations that

can attack fires earlier in the fire development process present lower

risk to firefighters. The longer the duration of the fire development

process without intervention, the greater the increase in risk for

occupants and responding firefighters. Therefore, time is critical.

Stopping the escalation of the event involves firefighter

intervention via critical tasks performed on the fireground.

Critical tasks, as described previously, include those tasks that

directly affect the spread of fire as well as the associated structural

tenability.

There are windows of opportunity to complete critical tasks. A fire

in a structure with a typical residential fuel load at six minutes

post-ignition is very different from the same fire at eight minutes or at

ten minutes post-ignition. Some tasks that are deemed“important”

(e.g.,scene size-up) for a fire in early stages of growth become critical

if intervention tasks are delayed. Time can take away opportunities. If

too much time passes, then the window of opportunity to affect

successful outcomes (e.g.,rescue victim or stop fire spread) closes.

For a typical structure fire event involving a fire department

response, there is an incident commander on the scene who

determines both the strategy and tactics that will be employed to

stop the spread of the fire, rescue occupants, ventilate the

structure, and ultimately extinguish the fire. Incident

commanders must deal with the fire in the present and make

intelligent command decisions based on the circumstances at

hand upon arrival. Additionally, arrival time and crew size are

factors that contribute to the incident commander’s decisions and

affect the capability of the firefighters to accomplish necessary

tasks on scene in a safe, efficient, and effective manner.

Table 9 illustrates vividly the more dangerous conditions small

crews face because of the extra time it takes to begin and complete

critical tasks (particularly fire suppression). In the two minutes

more it took for the two-person crew (early arrival) than the

five-person crew (early arrival) to get water on the fire, a slow

growth rate fire would have increased from 1.1 MW to 1.5 MW.

This growth would have been even more extreme for a

medium-or fast-growth rate fire. The difference is even more

substantial for the two-person crew with late arrival as the fire

almost doubled in size in the time difference between this crew

and the five-person crew.

Based on fire modeling for the low hazard structure studied with a

typical residential fuel load, it is likely that medium- and fast-growth

rate fires will move beyond the room of origin prior to the arrival of

firefighters for all crew sizes. Note that results in Table 8 included

only the close-stagger rescue time data. The effect of far-stagger

rescue times on occupant tenability should be investigated in future

studies. Therefore, the risk level of the event upon arrival will be

higher for all crews which must be considered by the incident

commander when assigning firefighters to on-scene tasks.

Figure 56: Average FED Curves for Early Arrival for All Crew Sizes

at Fast-Growth Fires

Table 9: Fire Size at Time of Fire Suppression

Remote Room Tenability for Fast Fires

Deployment Time to Water Fire Size at Time of

Configuration on Fire Suppression for

Slow-Growth Fires

2-Person, Late Arrival 14:26 2.1 MW

2-Person, Early Arrival 12:26 1.5 MW

3-Person, Late Arrival 13:24 1.8 MW

3-Person, Early Arrival 11:24 1.3 MW

4-Person, Late Arrival 13:11 1.7 MW

4-Person, Early Arrival 11:11 1.3 MW

5-Person, Late Arrival 12:33 1.6 MW

5-Person, Early Arrival 10:33 1.1 MW

49

(Min : Sec)
Reports on firefighter fatalities consistently document

overexertion/overstrain as the leading cause of line-of-duty

fatalities. There is strong epidemiological evidence that

heavy physical exertion can trigger sudden cardiac events

(Mittleman et al. 1993; Albert et al. 2000). Therefore, information

about the effect of crew size on physiological strain is very

valuable.

During the planning of the fireground experiments,

investigators at Skidmore College recognized the opportunity to

conduct an independent study on the relationship between

firefighter deployment configurations and firefighter heart rates.

With the approval of the Institutional Review Board of Skidmore

College, they were able to leverage the resources of the field

experiments to conduct a separate analysis of the cardiac strain

on fire fighters on the fireground.

For details, consult the complete report (Smith 2009). Two

important conclusions from the report reinforce the importance

of crew size:

 Average heart rates were higher for members of small crews,

particularly two-person crews.

 Danger is increased for small crews because the stress of fire

fighting keeps heart rates elevated beyond the maximum heart

rate for the duration of a fire response, and so the higher heart

rates were maintained for sustained time intervals.

Physiological Effects of Crew Size on Firefighters

50
Study Limitations

The scope of this study is limited to understanding the

relative influence of deployment variables to low-hazard,

residential structure fires, similar in magnitude to the

hazards described in NFPA 1710. The applicability of the

conclusions from this report to commercial structure fires,

high-rise fires, outside fires, terrorism/natural disaster response,

HAZMAT or other technical responses has not been assessed and

should not be extrapolated from this report.

Every attempt was made to ensure the highest possible degree of

realism in the experiments while complying with the

requirements of NFPA 1403, but the dynamic environment on the

fireground cannot be fully reproduced in a controlled experiment.

For example, NFPA 1403 required a daily walkthrough of the burn

prop (including identifying the location of the fire) before

ignition of a fire that would produce an Immediately Dangerous

to Life and Health (IDLH) atmosphere, a precaution not available

to responders dispatched to a live fire.

The number of responding apparatus for each fireground

response was held constant (three engines and one truck, plus the

battalion chief and aide) for all crew size configurations. The

effect of deploying either more or fewer apparatus to the scene

was not evaluated.

The fire crews who participated in the experiments typically

operate using three-person and four-person staffing. Therefore,

the effectiveness of the two-person and five-person operations

may have been influenced by a lack of experience in operating at

those staffing levels. Standardizing assigned tasks on the

fireground was intended to minimize the impact of this factor,

which has an unknown influence on the results.

The design of the experiments controlled for variance in

performance of the incident commander. In other words, a

more-or less-effective incident commander may have a significant

influence on the outcome of a residential structure fire.

Although efforts were made to minimize the effect of learning

across experiments, some participants took part in more than one

experiment, and others did not.

The weather conditions for the experiments were moderate to

cold. Frozen equipment such as hydrants and pumps was not a

factor. However, the effect of very hot weather conditions on

firefighter performance was not measured.

All experiments were conducted during the daylight hours.

Nighttime operations could pose additional challenges.

Fire spread beyond the room of origin was not considered in the

room and contents tests or in the fire modeling. Therefore, the

size of the fire and the risk to the firefighter may be somewhat

underestimated for fast-growing fires or slower-response

configurations.

There is more than one effective way to perform many of the

required tasks on the fireground. Attempts to generalize the

results from these experiments to individual departments must

take into account tactics and equipment that vary from those used

in the experiments.

51
Conclusions

More than 60 laboratory and full-scale fire experiments were

conducted to determine the impact of crew size, first-due

engine arrival time, and subsequent apparatus arrival

times on firefighter safety and effectiveness at a low-hazard

residential structure fire. This report quantifies the effects of

changes to staffing and arrival times for low-hazard residential

firefighting operations. While resource deployment is addressed in

the context of a single structure type and risk level, it is recognized

that public policy decisions regarding the cost-benefit of specific

deployment decisions are a function of many factors including

geography, available resources, community expectations, as well as

all local hazards and risks. Though this report contributes

significant knowledge to community and fire service leaders in

regard to effective resource deployment for fire suppression, other

factors contributing to policy decisions are not addressed.

The objective of the experiments was to determine the relative

effects of crew size, first-due engine arrival time, and stagger time

for subsequent apparatus on the effectiveness of the firefighting

crews relative to intervention times and the likelihood of occupant

rescue using a parametric design. Therefore, the experimental

results for each of these factors are discussed below.

Of the 22 fireground tasks measured during the experiments, the

following were determined to have especially significant impact on

the success of fire fighting operations. Their differential outcomes

based on variation of crew size and/or apparatus arrival times are

statistically significant at the 95 % confidence level or better.

Overall Scene Time:

The four-person crews operating on a low-hazard structure fire

completed all the tasks on the fireground (on average) seven

minutes faster — nearly 30 % — than the two-person crews. The

four-person crews completed the same number of fireground tasks

(on average) 5.1 minutes faster — nearly 25 % — than the

three-person crew. For the low-hazard residential structure fire,

adding a fifth person to the crews did not decrease overall fireground

task times. However, it should be noted that the benefit of five-person

crews has been documented in other evaluations to be significant for

medium- and high-hazard structures, particularly in urban settings,

and should be addressed according to industry standards.

18

Time to Water on Fire:

There was a nearly 10 % difference in the “water on fire time”

between the two and three-person crews and an additional 6 %

difference in the “water on fire time” between the three- and

four-person crews (i.e., 16 % difference between the four and

two-person crews). There was an additional 6 % difference in the

“water on fire’” time between the four- and five-person crews (i.e.,

22 % difference between the five and two-person crews).

Ground Ladders and Ventilation:

The four-person crew operating on a low-hazard structure fire

can complete laddering and ventilation (for life safety and rescue)

30 % faster than the two-person crew and 25 % faster than the

three-person crew.

Primary Search:

The three-person crew started and completed a primary search

and rescue 25 % faster than the two-person crew. In the same

structure, the four- and five-person crews started and completed a

primary search 6 % faster than the three-person crews and 30 %

faster than the two-person crew. A 10 % difference was equivalent

to just over one minute.

Hose Stretch Time:

In comparing four-and five-person crews to two-and three-person

crews collectively, the time difference to stretch a line was 76 seconds.

In conducting more specific analysis comparing all crew sizes to a

two-person crew the differences are more distinct. A two-person crew

took 57 seconds longer than a three-person crew to stretch a line. A

two-person crew took 87 seconds longer than a four-person crew to

complete the same tasks. Finally, the most notable comparison was

between a two-person crew and a five-person crew — more than 2

minutes (122 seconds) difference in task completion time.

Industry Standard Achieved:

The “industry standard achieved” time started from the first

engine arrival at the hydrant and ended when 15 firefighters were

assembled on scene.

19 An effective response force was assembled

by the five-person crews three minutes faster than the four-person

crews. According to study deployment protocal, the two- and

three-person crews were unable to assemble enough personnel to

meet this standard.

Occupant Rescue:

Three different “standard” fires(slow-, medium-, and fast-growth

rate) were simulated using the Fire Dynamics Simulator(FDS) model.

The fires grew exponentially with time. The fire modeling simulations

demonstrated that two-person, late arriving crews can face a fire that is

twice the intensity of the fire faced by five-person, early arriving crews.

The rescue scenario was based on a nonambulatory occupant in an

upstairs bedroom with the bedroom door open.

Independent of fire size, there was a significant difference between

the toxicity, expressed as fractional effective dose (FED), for

occupants at the time of rescue depending on arrival times for all

crew sizes. Occupants rescued by crews starting tasks two minutes

earlier had lesser exposure to combustion products.

The fire modeling showed clearly that two-person crews cannot

complete essential fireground tasks in time to rescue occupants

without subjecting either firefighters or occupants to an

increasingly hazardous atmosphere. Even for a slow-growth rate

fire, the FED was approaching the level at which sensitive

populations, such as children and the elderly are threatened. For a

medium-growth rate fire with two-person crews, the FED was far

above that threshold and approached the level affecting the median

sensitivity in general population. For a fast-growth rate fire, the

FED was well above the median level at which 50 % of the general

population would be incapacitated. Larger crews responding to

slow-growth rate fires can rescue most occupants prior to

incapacitation along with early-arriving larger crews responding to

medium-growth rate fires. The result for late-arriving (two

minutes later than early-arriving) larger crews may result in a threat

to sensitive populations for medium-growth rate fires.” The new

sentence is consistent with our previous description for two-person

crews where we identify a threat to sensitive populations..

Statistical averages should not, however, mask the fact that there is

no FED level so low that every occupant in every situation is safe.

52

18 NFPA Standard 1710 - A.5.2.4.2.1 ...Other occupancies and structures in the community that present greater hazards should be addressed by additional fire fighter

functions and additional responding personnel on the initial full alarm assignment.

19 NFPA 1710 Standard for the Organization and Deployment of Fire Suppression Operations, Emergency Medical Operations, and Special Operations to the Public by

Career Fire Departments. Section 5.2.1 – Fire Suppression Capability and Section 5.2.2 Staffing.
53

Summary:

The results of these field experiments contribute significant

knowledge to the fire service industry. First, the results establish a

technical basis for the effectiveness of company crew size and arrival

time in NFPA 1710. The results also provide valid measures of total

effective response force assembly on scene for fireground operations,

as well as the expected performance of time-to-critical-task

measures for a low-hazard structure fires. Additionally, the results

provide tenability measures associated with the occupant exposure

rates to the range of fires considered by the fire model.
54

I

n order to realize a significant reduction in firefighter

line-of-duty death (LODD) and injury, fire service leaders must

focus directly on resource allocation and the deployment of

resources, both contributing factors to LODD and injury. Future

research should use similar methods to evaluate firefighter

resource deployment to fires in medium- and high-hazard

structures, including multiple-family residences and commercial

properties. Additionally, resource deployment to

multiple-casualty disasters or terrorism events should be studied

to provide insight into levels of risks specific to individual

communities and to recommend resource deployment

proportionate to such risk. Future studies should continue to

investigate the effects of resource deployment on the safety of

both firefighters and the civilian population to better inform

public policy.

Future Research
55

Acknowledgements

Aproject of this magnitude extends significantly beyond the

capabilities and expertise of the report authors. The

following individuals were instrumental in the success of

the experiments:

 Technical Experts — Dennis Compton, Retired Chief from

Mesa, AZ and consultant, IFSTA; Russell Sanders, Retired

Chief from Louisville, KY and staff, NFPA; William “Shorty”

Bryson, Retired Chief of Miami, FL and Past President of

Metropolitan Fire Chiefs; David Rohr, Operations Chief from

Fairfax County Fire and Rescue; Richard Bowers, Chief from

Montgomery County Fire and Rescue Department; Vincent

Dunn, Retired from Fire Department of New York; Michael

Clemens, Chief of Training from Montgomery County Fire

and Rescue Department; James Walsh, Battalion Chief from

Fairfax County Fire and Rescue; Larry Jenkins, Captain I from

Fairfax County Fire and Rescue; Doug Hinkle, Training

Captain from Montgomery County Fire and Rescue

Department; and Paul Neal, Safety Officer for Montgomery

County Fire and Rescue Department.

 Montgomery County Fire Department – Former Chief Tom

Carr and Chief Richard Bowers — AND Fairfax County Fire

and Rescue Services — Chief Ronald Mastin for supporting

this study over a period of years to an unprecedented degree.

 NIST experimental and modeling personnel - Michael

Selepak, Roy McLane, Anthony Chakalis, Andrew Lock, Marco

Fernandez, Ed Hnetkovsky, Jay McElroy, Lauren DeLauter,

Glenn Forney, Dan Murphy, and Craig van Norman.

 IAFF Staff/ Data Entry/ Timer Supervision/Heart Rate

Monitors– Nicole Taylor, Randy Goldstein, and Ron Benedict

 Skidmore College – Denise Smith and Polar Heart Rate

Monitors for supplemental study to bolster the significance of

the main study results.

 Timers — DeWayne Dutrow — Lead, Cliff Berner, Michael

Fleming, Colby Poore, Chris Maple, Michael Thornton,

Robert Daley, Ryan Loher

 Montgomery County Support Services — Joey Fuller III —

Lead, Chris Hinkle, Doug Dyer, Joey Fuller IV

 The dedicated Fire Officers and Firefighters from

Montgomery County Fire & Rescue and Fairfax County Fire

& Rescue, who performed the difficult work of structural fire

fighting safely and courageously.
56

References

 Albert CM, Mittleman MA, Chae CU, Lee IM, Hennekens CH,

Manson JE (2000). Triggering of sudden death from cardiac

causes by vigorous exertion. N Engl J Med

343(19):1355-1361.

 Backoff, R. W.; et al. (1980). Firefighter Effectiveness - A

Preliminary Report. Columbus Fire Division, The Ohio State

University.

 Barnard RJ, Duncan HW [1975]. Heart rate and ECG

responses of firefighters. J Occup Med 17: 247-250.

 Blevins, L. G. and Pitts, W. M. (1999). Modeling of Bare and

Aspirated Thermocouples in Compartment Fires. Fire Safety

Journal,Vol. 33, 239-259.

 Bryant, R. A., et al. (2004). The NIST 3 Megawatt Quantitative

Heat Release Rate Facility - Description and Procedure. Natl.

Inst. Stand. Technol. NIST IR 7052

 Centaur Associates. (1982). Report on the Survey of Fire

Suppression Crew Size Practices.

 Center for Public Safety Excellence. (2008.) CFAI:

STANDARDS OF COVER, FIFTH EDITION. Chantilly,Va.

 Center for Public Safety Excellence. (2009.) FIRE &

EMERGENCY SERVICE SELF-ASSESSMENT MANUAL.

Chantilly,VA.

 Chang, C. Huang, H. (2005). A Water Requirements

Estimation Model for Fire Suppression: A Study Based on

Integrated Uncertainty Analysis, Fire Technology,Vol. 41, NO.

1, Pg. 5.

 Coleman, Ronny J. (1988). MANAGING FIRE SERVICES,

2nd Edition, International City/County Management

Association, Washington, DC.

 Cushman, J. (1982). Report to Executive Board, Minimum

Manning as Health & Safety Issue. Seattle, WA Fire

Department, Seattle, WA.

 Gerard, J.C. and Jacobsen, A.T. (1981). Reduced Staffing: At

What Cost?, Fire Service Today, Pg. 15.

 Fahy R (2005). U.S. Firefighter Fatalities Due to Sudden

Cardiac Death 1995-2004. NFPA Journal. 99(4): 44-47.

 Hall, John R. Jr. (2006). U.S Unintentional Fire Death Rates by

State. National Fire Protection Association, Quincy, MA.

 Huggett, C. (1980). Estimation of the Rate of Heat Release by

Means of Oxygen Consumption. J. of Fire and Flammability,

Vol. 12, pp. 61-65.

 International Association of Fire Fighters/John’s Hopkins

University. (1991). “Analysis of Fire Fighter Injuries and

Minimum Staffing Per Piece of Apparatus in Cities With

Populations of 150,000 or More,” December 1991.

 ISO (2007). ISO 13571: Life-threatening Components of Fire

— Guidelines for the Estimation of Time Available for Escape

Using Fire Data, International Standards Organization,

Geneva.

 Janssens, M. L. (1991). Measuring Rate of Heat Release by

Oxygen Consumption., Fire Technology,Vol. 27, pp. 234-249.

 Jones, W. W. (2000). Forney, G. P.; Peacock, R. D.; Reneke, P. A.

Technical Reference for CFAST: An Engineering Tool for

Estimating Fire and Smoke Transport. National Institute of

Standards and Technology, Gaithersburg, MD. NIST TN 1431;

190 p. March 2000.

 Karter, M.J. Jr. (2008). U.S. Fire Loss for 2007. NFPA Journal,

September/October 2008.

 McGrattan, K. B. (2006). Fire Dynamics Simulator (Version

4): Technical Reference Guide. NIST Gaithersburg, MD. NIST

SP 1018; NIST Special Publication 1018; 109 p. March 2006.

 McManis Associates and John T. O’Hagan and Associates

(1984). “Dallas Fire Department Staffing Level Study,” June

1984; pp. I-2 & II-1 through II-7.

 Menker, W.K. (1994). Predicting Effectiveness of Manual

Suppression, MS Thesis, Worcester Polytechnic Institute.

 Metro Chiefs/International Association of Fire Chiefs (1992)

“Metro Fire Chiefs - Minimum Staffing Position,” May 1992.

 Mittleman MA, Maclure M, Tofler GH, Sherwood JB,

Goldberg RJ, Muller JE (1993). Triggering of acute myocardial

infarction by heavy physical exertion. N Engl J Med

329(23):1677–1683.

 Morrison, R. C. (1990). Manning Levels for Engine and

Ladder Companies in Small Fire Departments National Fire

Academy, Emmitsburg, MD.

 NFA (1981). Fire Engines are Becoming Expensive Taxi Cabs:

Inadequate Manning. National Fire Academy, United States

Fire Administration, Emmitsburg, MD.

 NFPA (2007). NFPA 1403: Standard on Live Fire Training

Evolutions. National Fire Protection Association, Quincy,

MA.

 NFPA (2004). NFPA 1710: Standard for the Organization and

Deployment of Fire Suppression Operations, Emergency

Medical Operations, and Special Operations to the Public by

Career Fire Departments. National Fire Protection

Association, Quincy, MA.

 NFPA (2008). Fire Protection Handbook, 20th Edition.

National Fire Protection Association, Quincy, MA.
57

 Office of the Fire Marshal of Ontario. (1993). Fire Ground

Staffing and Delivery Systems Within a Comprehensive Fire

Safety Effectiveness Model. Ministry of the Solicitor General,

Toronto, Ontario, Canada.

 Omega Engineering, Inc. (2004). The Temperature

Handbook. 5th Edition.

 Parker, W. J. (1984). Calculations of the Heat Release Rate by

Oxygen-Consumption for Various Applications., Journal of

Fire Sciences,Vol. 4, pp. 380-395.

 Phoenix, AZ Fire Department,” Fire Department Evaluation

System (FIREDAP),” December 1991; p. 1.

 Purser, D. (2002). “Toxicity Assessment of Combustion

Products.” In The SFPE Handbook of Fire Protection

Engineering, 3rd Edition. DiNenno (Editor). National Fire

Protection Association, Quincy, MA.

 Rand Institute. (1978). Fire Severity and Response Distance:

Initial Findings. Santa Monica, CA.Roberts, B.

 Romet TT, Frim J (1987). Physiological responses to

firefighting activities. Eur J Appl Physiol 56: 633-638.

 Sardqvist, S; Holmsted, G., Correlation Between Firefighting

Operation and Fire Area: Analysis of Statistics, Fire

Technology,Vol. 36, No. 2, Pg. 109, 2000

 Smith DL, Petruzzello SJ, Kramer JM, Warner SE, Bone BG,

Misner JE (1995). Selected physiological and psychobiological

responses of physical activity in different configurations of

firefighting gear. Ergonomics 38(10): 2065-2077

 Smith, D. Effect of Deployment of Resources on

Cardiovascular Strain of Firefighters.” DHS, 2009.

 Thornton, W. (1917). The Relation of Oxygen to the Heat of

Combustion of Organic Compounds., Philosophical

Magazine and J. of Science,Vol. 33.

 TriData Corporation. The Economic Consequences of

Firefighter Injuries and Their Prevention, Final Report.

National Institute of Standards and Technology, U.S.

Department of Commerce, Gaithersburg, MD. 2005.

 USFA (2002). Firefighter Fatality Retrospective Study. United

States Fire Administration

 USFA (2008). Fatal Fires,Vol. 5-Issue 1, March 2005. USFA,

Firefighter Fatalities in the United States in 2007. June 2008.

Prepared by C2 Technologies, Inc., for U.S. Fire

Administration, Contract Number EME-2003-CO-0282.

 USNRC (2007).Verification and Validation of Selected Fire

Models for Nuclear Power Plant Applications.Volume 2:

Experimental Uncertainty. Washington, DC : United States

Nuclear Regulatory Commission. 1824.
58
59

APPENDIX A: Laboratory Experiments

The fire suppression and

resource deployment

experiments consisted of

four distinct parts: laboratory

experiments, time-to-task

experiments, room and contents

experiments and fire modeling.

The purpose of the laboratory

experiments was to assure a fire

in the field experiments that

would consistently meet NFPA

1403 requirements for live fire

training exercises. The

laboratory experiments enabled

investigators to characterize the

burning behavior of the wood

pallets as a function of:

 number of pallets and the

subsequent peak heat release

rate

 compartment effects on burning of wood pallets

 effect of window ventilation on the fire

 effect on fire growth rate of the loading configuration of

excelsior (slender wood shavings typically used as packing

material)

Design and Construction

Figure A-1 shows the experimental configuration for the

compartment pallet burns. Two identically sized compartments

(3.66 m x 4.88 m x 2.44 m) were connected by a hallway (4 m x 1 m

x 2.4 m). At each end of the hallway, a single door connected the

hallway to each of the compartments. In the burn compartment, a

single window (3 m x 2 m) was covered with noncombustible

board that was opened for some experiments and closed for others.

At the end of test, it was opened to extinguish the remaining

burning material and to remove any debris prior to the next test. In

the second compartment, a single doorway connected the

compartment to the rest of the test laboratory. It was kept open

throughout the tests allowing the exhaust to flow into the main

collection hood for measurement of heat release rate.

The structure was constructed of two layer of gypsum wallboard

over steel studs. The floor of the structure was lined with two

layers of gypsum wallboard directly over the concrete floor of the

test facility. In the burn compartment, an additional lining of

cement board was placed over the gypsum walls and ceiling

surfaces near the fire source to minimize fire damage to the

structure after multiple fire experiments. A doorway 0.91 m wide

by 1.92 m tall connected the burn compartment to the hallway

and an opening 1 m by 2 m connected the hallway to the target

compartment. Ceiling height was 2.41 m throughout the

structure, except for the slight variation in the burn room.

Fuel Source

The fuel source for all of the tests was recycled hardwood pallets

constructed of several lengths of hardwood boards nominally 83

mm wide by 12.7 mm thick. Lengths of the individual boards

ranged from nominally 1 m to 1.3 m. The finished size of a single

pallet was approximately 1 m by 1.3 m by 0.11 m. Figure A-2

shows the fuel source for one of the tests including six stacked

pallets and excelsior ignition source. For an ignition source,

excelsior was placed within the pallets, with the amount and

location depending on the ignition scenario. Figure A-3 shows

the pallets prior to a slow and a fast ignition scenario fire. Table

A-1 details the total mass of pallets and excelsior for each of the

free burn and compartment tests.

Experimental Conditions

The experiments were conducted in two series. In the first

series, heat release measurements were made under free burn

conditions beneath a 6 m by 6 m hood used to collect combustion

gases and provide the heat release rate (HRR) measurement. A

second series of tests was conducted with the fire in a

compartmented structure to assess environmental conditions

within the structure during the fires and determine the effect of

the compartment enclosure on the fire growth. Table A-1 presents

a summary of the tests conducted.

Figure A-1. Compartment Configuration and Instrumentation for Pallet Tests

Figure A-2. Pallets and Excelsior Ignition Source

Used as a Fuel Source
60

Measurements Conducted

Heat release rate (HRR) was measured in all tests. HRR

measurements were conducted under the 3 m by 3 m calorimeter

at the NIST Large Fire Research Laboratory. The HRR

measurement was based on the oxygen consumption calorimetry

principle first proposed by Thornton (Thornton 1917) and

developed further by Huggett (Huggett 1980) and Parker (Parker

1984). This method assumes that a known amount of heat is

released for each gram of oxygen consumed by a fire. The

measurement of exhaust flow velocity and gas volume fractions

(O2, CO2 and CO) were used to determine the HRR based on the

formulation derived by Parker (Parker 1984) and Janssens

(Janssens 1981). The combined expanded relative uncertainty of

the HRR measurements was estimated at ± 14 %, based on a

propagation of uncertainty analysis (Bryant 2004).

For the compartment fire tests, gas temperature measurements

were made in the burn compartment and in the target

compartment connected by a hallway to the burn compartment

using 24 gauge bare-bead chromel-alumel (type K)

thermocouples positioned in vertical array. Thermocouples were

located at the center of each compartment at locations 0.03 m,

0.30 m, 0.61 m, 0.91 m, 1.22 m, 1.52 m, 1.83 m, and 2.13 m from

the ceiling. The expanded uncertainty associated with a type K

thermocouple is approximately ± 4.4oC. (Omega 2004)

Gas species were continuously monitored in the burn

compartment at a level 0.91 m from the ceiling at a location

centered on the side wall of the compartment, 0.91 m from the

wall. Oxygen was measured using paramagnetic analyzers.

Carbon monoxide and carbon dioxide were measured using

non-dispersive infrared (NDIR) analyzers. All analyzers were

calibrated with nitrogen and a known concentration of gas prior

to each test for a zero and span concentration calibration. The

expanded relative uncertainty of each of the span gas molar

fractions is estimated to be ± 1 %.

Total heat flux was measured on the side wall of the enclosure at

a location centered on the side wall, 0.61 m from the ceiling level.

The heat flux gauges were 6.4 mm diameter Schmidt-Boelter type,

water cooled gauges with embedded type-K thermocouples (see

Figure A-4). The manufacturer reports a ± 3 % expanded

uncertainty in the response calibration (the slope in kW/m2

/mV).

Calibrations at the NIST facility have varied within an additional

± 3 % of manufacturer’s calibration. For this study, an uncertainty

of ± 6 % is estimated.

Table A-1. Tests Conducted and Ambient Conditions

at Beginning of Each Test

Notes: PAL stands for “pallet” and CRA (“Community Risk

Assessment”) is the designator for the configuration of pallets

burned in the compartment. Efforts were made to use the same

amount of excelsior mass for CRA 2 (~0.8 kg), but the value was

not measured.

Figure A-3. Fuel and Excelsior Source for Slow (top)

and Fast (bottom) Ignition Scenarios Figure A-4: Heat Flux Gauge with Radiation Shielding
61

Results

Table A-2 shows the peak HRR and time to peak HRR for the

free burn tests and for the compartment tests. Figure A-5 includes

images from the free burn experiments near the time of peak

HRR for each of the experiments. Figure A-6 illustrates the

progression of the fire from the exit doorway looking down the

hallway to the burn compartment for one of the tests. Figure A-7

to Figure A-10 present graphs of the heat release rate for all of the

tests. Figure A-11 through Figure A-15 shows the gas temperature,

major gas species concentrations, and heat flux in the burn

compartment and target compartment in the five compartment

tests.

Table A-2. Peak Heat Release Rate During Several Pallet

Tests in Free-burn and in a Compartment

Figure A-5. Free-Burn Experiments Near Time of Peak Burning
62

Figure A-6. Example Fire Progression from Test CRA 1

Figure A-7. HRR, Slow Ignition, Free Burn Scenario

Figure A-8. HRR, Fast Igntion, Free Burn Scenario

Figure A-9. HRR, Slow Ignition, Compartment Test

Figure A-10. HRR, Fast Ignition, Compartment Test
63

Figure A-11. Temperature, Gas Concentration, and Heat Flux During Test CRA 1, 6 Pallets, Slow Ignition Scenario
64

Figure A-12. Temperature, Gas Concentration, and Heat Flux During Test CRA 2, 4 Pallets, Slow Ignition Scenario
65

Figure A-13. Temperature, Gas Concentration, and Heat Flux During Test CRA 3, 4 Pallets, Fast Ignition Scenario
66

Figure A-14. Temperature, Gas Concentration, and Heat Flux During Test CRA 4, 4 Pallets, Slow Ignition Scenario (Replicate)
6

7

FigureA-15.Temperature,GasConcentration,andHeatFluxDuringTestCRA5,4Pallets,SlowIgnitionScenario

(OpenWindowVenting)
68

Based upon the results of the laboratory experiments, the

project team determined that four pallets would provide

both a realistic fire scenario, as well as a repeatable and

well-characterized fuel source. Varying the placement and

quantity of excelsior provided significant variance in the rate of

fire growth. Prior to finalization of the fuel package and

construction specifications, modeling was used to ensure that the

combination of fuel and residential geometry would result in

untenable conditions throughout the structure without subjecting

the firefighters to unsafe testing conditions. Therefore, CFAST

(the consolidated fire and smoke transport model (Jones 2000))

and FDS (fire dynamics simulator model (McGrattan 2006)) were

used to predict the temperatures and toxic species within the

structure as a function of the experimentally determined heat

release rates. The results summarized below confirmed that the

building geometry and fuel package produced adequate variation

in tenability conditions in the residential structure and ensured

that the room of origin would not reach flashover conditions (a

key provision of NFPA 1403). Meeting these conditions provided

the foundation for experiments to meet the two primary objectives

of fire department response: preservation of life and property.

APPENDIX B: Designing Fuel Packages for Field Experiments

Figure B-1: Time-dependent temperature contours in field structure with fast growth fire

Figure B-2: Time-dependent smoke density contours in field structure with fast growth fire

Figure B-1 and B-2 show the thermal and smoke

conditions in the residential structure at different time

periods using the fast growth, four pallet fuel package.

The results of the fire modeling indicated development

of untenable conditions in the field experiments

between 5 and 15 minutes, depending upon several

factors: fire growth rate, ventilation conditions, the total

leakage of heat into the building and through leakage

paths, and firefighter intervention. This time frame

allowed for differentiation of the effectiveness of various

fire department deployment models.
69

Through the generosity of the Montgomery County (MD),

an open space was provided to construct a temporary burn

prop at the Montgomery County Fire and Rescue Training

Facility in Rockville, MD. The area had ready access to water and

electrical utilities. A licensed general contractor was retained,

including a structural engineer for the design of critical ceiling

members, and the burn prop was constructed over a several

month period in late 2008.

The burn prop consisted of two 2,000 ft.

2 (186 m2

) floors

totaling 4,000 ft.

2 (

372 m2). An exterior view of two sides of the

burn prop is shown in Figure C-1.

Additional partitions were installed by NIST staff to create a

floor plan representative of a two-story, 186 m2 (2,000 ft.

2

) single

family residence. Note that the structure does not have a

basement and includes no exposures. The overall dimensions are

consistent with the general specifications of a typical low hazard

residential structure that many fire departments respond to on a

regular basis, as described in NFPA 1710.

Further details about typical single family home designs are not

provided in the standard. Therefore, a floor plan representative of

a typical single family home was created by the project team.

Details and floor plan dimensions are shown in Figure C-2.

The black lines indicate load-bearing reinforced concrete walls

and red lines indicate the gypsum over steel stud partition walls.

The ceiling height, not shown in Figure C-2, is 94 in. (2.4 m)

throughout the entire structure except in the burn compartments,

where the ceiling height is 93 in. (2.4 m). The purpose of the

partition walls was to symmetrically divide the structure about

the short axis in order to allow one side of the test structure to

cool down and dry-out after a fire test with suppression while

conducting experiments on the other side.

The concrete walls original to the burn prop were 8 in. (204 mm

) thick steel reinforced poured

concrete and the floors on the first

level and second levels were 4 in.

(102 mm) thick poured concrete.

The support structure for the

second floor and the roof

consisted of corrugated metal pan

welded to open web steel joists.

The dimensions of the joists are

shown in Figure C-3. The ceiling

was constructed from 1⁄2 in. (13

mm) thick cement board fastened

to the bottom chord of the steel

joists. Partition walls were

constructed from 5/8 in. (17 mm)

thick gypsum panels attached to

20 gauge steel studs fastened to

steel track, spaced 16 in. (407

mm) on center.

Additional construction was

implemented in the burn

compartments to address thermal

loading and hose stream

impingement concerns. Spray-on

fireproofing was applied to the

steel joists prior to fastening the

ceiling, as shown in Figure C-4.

The ceilings were constructed

with three layers of 1⁄2 in. (13 mm)

cement board, as opposed to one

layer construction in the rest of

the building. Each layer was

fastened in a different direction so

that seams of adjacent layers ran

orthogonally. The difference in

ceiling heights previously

APPENDIX C: Temporary Burn Prop Construction and Instrumentation

Figure C-1: View of two sides of the burn prop

Figure C-2: Dimensions of the Burn Prop Floor Plan
70

mentioned is the result of the two additional sheets of cement

board. The burn compartment walls were constructed from a

single layer of 1⁄2 in. (13 mm) cement board over a single layer of

5/8 in. (16 mm) gypsum board, attached to 7/8 in. (22 mm) offset

metal furring strips. Particular care was taken so that all ceiling

and partition wall seams were filled with chemically-setting type

joint compound to prevent leakage into the interstitial space

between the ceiling and the floor above. After construction of the

ceiling was complete, a dry-standpipe deluge system was installed

with one head in each burn room to provide emergency

suppression. During an experiment, a 2.5 in. (104 mm) ball valve

fitting was attached and charged from a nearby hydrant. Figure

C-5 was taken during the process of replacing “worn out” ceiling

panels and shows the additional construction implemented in the

burn room as well as the deluge sprinkler head.

Windows and exterior doors were constructed to be

non-combustible. Windows were fabricated from 0.25 in. (10

mm) thick steel plate and the exterior doors were of prefabricated

hollow-core steel design. The windows on the first floor were 30

in. (0.76 m) width x 36 in. (0.91 m) height and 36 in. (0.91 m)

width x 40 in. (1.02 m) height on the second floor. Exterior doors

were 35.8 in. (0.88 m) width x 80.5 in. (2.03 m) height. There

were no doors attached to the doorways inside the structure.

Figure C-6 shows the construction of the burn prop windows as

well as the NFPA 1403-compliant latch mechanism. Figure C-7 is

a picture of the interior of the burn prop taken just outside the

burn compartment, showing the construction of the ceiling,

interior doorway construction, gypsum wing wall and the joint

compound used to seal seams in the ceiling and walls.

Instrumentation

After construction, the instrumentation to measure the

propagation of products of combustion was installed throughout

the burn prop. The instrumentation plan was designed to measure

gas temperature, gas concentrations, heat flux, visual obscuration,

video, and time during the experiments. The data were recorded at

intervals of 1 s on a computer based data acquisition system. A

schematic plan view of the instrumentation arrangement is shown

in Figure C-8.

Table C-1 gives the locations of all of the instruments.

Measurements taken prior to

the compartment fire

experiments were length, wood

moisture content, fuel mass

and weather conditions

(relative humidity,

temperature, wind speed and

direction). Gas temperatures

were measured with two

different constructs of type K

(Chromel-Alumel)

thermocouples. All

thermocouples outside the

burn compartments were

fabricated from 30 gauge

glass-wrapped thermocouple

wire.Vertical arrays of three

thermocouples were placed

near the front door on the

north side and south sides of

the stairwell on the first floor.

On the second floor, vertical

arrays of eight thermocouples

were placed near the center of

each target room. Inside the

burn compartments, seven 3.2

mm (0.125 in.) exposed

junction thermocouples and

0.76 m (30 in.) SUPER

OMEGACLAD XL® sheathed

thermocouple probes were

arranged in a floor-to-ceiling

array. Figure C-9 shows the

vertical array in the burn

Figure C-3: Structural Steel Dimensions

Figure C-4: Fireproofing added to structural steel Figure C-5: Additional construction of burn room

walls and ceiling and deluge sprinkler head.

Figure C-6: Window & Latch Construction Figure C-7: Interior View of Burn Prop
71

compartment. Type K

thermocouple probes were

chosen because of their ability to

withstand high temperature,

moisture and physical abuse

resulting from physical contact

with hose streams and

firefighters. To protect the

extension wire and connectors

from the effects of heat and

water, through-holes were drilled

in the burn compartment walls

and the sheaths were passed

through from the adjacent

compartment. To prevent leakage

through the holes, all void spaces

were tightly packed with mineral

wool. Inside the burn

compartment the end of each

probe was passed through an

angle iron stand, and fastened to

the floor and ceiling to provide

additional protection from

physical contact with firefighters

and to ensure that the

measurement location remained

fixed throughout the

experiments. In consideration of

the risk associated with heating

the open web steel joists,

additional thermocouples were

placed above each burn

compartment to monitor the

temperature of the interstitial

space.

Figure C-8: Instrumentation & Furniture Prop Layout
Gas concentrations were sampled at the same location in each

target room. Both gas probes were plumbed to the same analyzer

and isolated using a switch valve; gas was only sampled at one

location during any given test. The gas sampling points were

located in the center of the West wall (C Side) of both rooms, 1.5

m (5 ft.) above the floor. The sampling tubes were connected to a

diaphragm pump which pulled the gas samples through stainless

steel probes into a sample conditioning system designed to

eliminate moisture in the gas sample. The dry gas sample was

then piped to the gas analyzer setup. In all of the experiments,

oxygen was measured using a paramagnetic analyzer and carbon

monoxide and carbon dioxide were measured using a

non-dispersive infrared (NDIR) analyzer. One floor-to-ceiling

thermocouple array was also co-located with each sample port

inlet.

Schmidt-Boelter heat flux gauges were placed in the North burn

room. One gauge was located 1.0 m (3.3 ft.) above the floor and

was oriented towards the fire origin (waste basket). This heat flux

gauge was placed to characterize the radiative heat flux at the face

piece level that would be experienced by a firefighter inside the

room. A second flux gauge was placed on the floor in order to

characterize the radiative heat flux from the upper layer and to

make an estimate of how close the room was to flashing over with

respect to time from ignition (using the common criteria of

flashover occurring at ~20kW/m2 at the floor level). The heat flux

gauges were co-located with the thermocouple probe array.

All length measurements were made using a steel measuring

tape. Wood moisture content measurements were taken using a

non-insulated-pin type wood moisture meter. Fuel mass was

measured prior to each experiment using a platform-style heavy

duty industrial scale. Mass was not measured after each

experiment because of the absorption of fire suppression water.

Publicly accessible Davis Vantage Pro2 weather instrumentation

(available via http://www.wunderground.com) located

approximately two miles from the experimentation site was used

to collect weather data in five minute intervals for the each day

that the experiments were conducted. Figure C-10 is a

photograph of the West wall of the North target room, showing

the thermocouple array, the smoke obscuration meter, and a gas

sampling probe used during the phase two experiments. The

layout is identical to that in the South target room.

Non-combustible “prop” furniture was fabricated from angle

iron stock and gypsum wallboard. The purpose of the furniture

was twofold. The furniture was placed inside the burn prop to

simulate realistic obstacles which obscure the search paths and

hose stream advancement. The second use for the furniture was so

that measurement instrumentation could be strategically placed

within the frame of the furniture. This served to protect

instrumentation from physical damage as a result of contact with

firefighters and their tools. Figure C-11 shows an example of a

table placed outside the burn room.

All instruments were wired to a centralized data collection room,

shown in Figure C-12, which was attached as a separate space on

one side of the building. This ensured physical separation for the

data collection personnel from the effects of the fire, while

minimizing the wire and tube lengths to the data logging

equipment. Note that the roof of the instrument room was

designed to serve as an additional means of escape for personnel

from the second floor of the burn prop through a metal door. A

railing was installed in order to minimize the fall risk in the event

that the emergency exit was required.

Figure C-9: Burn Room Thermocouple Array Figure C-10: Target Room Instrument Cluster

Figure C-11: Non-combustible “Prop” Table

72
73

Figure C-12: Instrumentation Room Outside Inside
74

Time-to-Task Data Collection Chart

Date ______________Start Time __________ End Time (all task complete) __________

Timer Name ________________________________________________________________

APPENDIX D: Data Collection and Company Protocols for Time-to-Task Tests
75

Tasks/Company

Arrive on Scene

- Arrive/ stop at hydrant

- Position engine

______________

- Layout report

- On-scene report

- Conduct size-up – 360o

lap – incident action plan – offensive

– detail incident (situation report)

- Transmit size-up to responding units

- Transfer command to chief

Establish Supply line

- Hydrant-Drop line (wrap)

- Position engine

- Pump engaged

- 4” straight lay

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

- Supply attack engine

Position attack line

- Flake

- Charge

- Bleed

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

- Advance

Establish - 2 in – 2 out

(Initial RIT)

Establish RIT

(Dedicated)

Company Protocols: Crew Size of 2

(10 total personnel on scene)

PLUS 4 RIC – 1403 = total 14 needed

Engine 1/2

Driver

Officer

-

Driver/O

Driver/O

Driver/O

Officer – (Not

interior—just

front door)

Officer

Truck 1/2

-Arrive

- 360o lap

Position Truck

Officer

O/D

O/D (performs

all RIT duties)

Engine 2/2

-Dry Lay – 2nd

engine takes

hydrant

- Charged

hydrant

– Supply attack

engine

Driver

Battalion Chief/ Aide

- Arrives

- Assumes Command

- Evaluates Resources

- Establishes

Command post

- Evaluates exposure

problems

- Directs hose

positioning

- Coordinates Units

- Transmits

Progress reports

- Changes strategy

- Orders, records, and

transmits results of

primary and

secondary searches

- Declares fire under

control

Engine 3/2
76

Tasks/Company

Gain/ Force Entry

Advance Line

- scan search fire room

- suppression

Deploy Back-up Line and protect

stairwell

Complete Primary Search

(in combo with Fire Attack)

Search Fire Floor

Search other Floors

Ventilation

(vent for fire or vent for life)

- Horizontal

- Ventilation

Ground Laddering – 2nd story

windows, front and side, for

firefighter means of egress and for

vertical ventilation – 24’/28’ and

roof ladder in case of vertical vent.

Control Utilities

(Interior and exterior)

Conduct Secondary Search

- Search Fire Floors

- Search other Floors

Check for Fire Extension

Open ceiling walls near fire on fire

floor

Check floor above for fire

extension

- wall breech

- ceiling breech

Mechanical Ventilation

Engine 1/2

Officer

(if officer commits

then he must pass

command)

Officer

Officer

Truck 1/2

O/D

Driver/Officer

Driver /Officer

Driver/Officer

Engine 2/2

Officer

Officer

Officer

Battalion Chief/ Aide Engine 3/2

O/D

O/D

Driver/Officer

O/D
77

Tasks/Company

Arrive on Scene

- Arrive/ stop at hydrant

- Position engine

______________

- Layout report

- On-scene report

- Conduct size-up – 360o

lap – incident action plan – offensive

– detail incident (situation report)

- Transmit size-up to responding units

- Transfer command to chief

Establish Supply line

- Hydrant-Drop line (wrap)

- Position engine

- Pump engaged

- 4” straight lay

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

- Supply attack engine

Position attack line

- Flake

- Charge

- Bleed

- Advance

Establish - 2 in – 2 out

(Initial RIT)

Establish RIT

(Dedicated)

Company Protocols: Crew Size of 3

(14 total personnel on scene)

PLUS 4 RIC – 1403 = total 18 needed

Engine 1/3

Driver

Officer

-

Driver

Driver

Driver

D/RB

Truck 1/3

-Arrive

- 360 degree lap

Position Truck

O/RB

Engine 2/3

Dry Lay – 2nd

engine takes

hydrant

Charged

hydrant –

Supply attack

engine

Driver

O/RB— advance

by foot to get to

point of entry –

performs all RIT

duties

Battalion Chief/ Aide

- Arrives

- Assumes Command

- Evaluates Resources

- Establishes

Command post

- Evaluates exposure

problems

- Directs hose

positioning

- Coordinates Units

- Transmits

Progress reports

- Changes strategy

- Orders, records, and

transmits results of

primary and

secondary searches

- Declares fire under

control

Engine 3/2
78

Tasks/Company

Gain/ Force Entry

Advance Line

- scan search fire room

- suppression

Deploy Back-up Line and

protect stairwell

Complete Primary Search

(in combo with Fire Attack)

Search Fire Floor

Search other Floors

Ventilation

(vent for fire or vent for life)

- Horizontal

- Ventilation

Ground Laddering – 2nd story

windows, front and side, for

firefighter means of egress and for

vertical ventilation – 24’/28’ and

roof ladder in case of vertical vent.

Control Utilities

(Interior and exterior)

Conduct Secondary Search

- Search Fire Floors

- Search other Floors

Check for Fire Extension

Open ceiling walls near fire on fire

floor

Check floor above for fire

extension

- wall breech

- ceiling breech

Mechanical Ventilation

Engine 1/3

O/RB

(if officer commits

then he must pass

command)

O/RB

Truck 1/3

O/RB

O/ RB

-

Driver

Driver

Driver (exterior)

O/RB (Interior)

O/RB

Driver

Engine 2/3 Battalion Chief/ Aide Engine 3/3

O/RB

Driver

Driver

Driver

(exterior)

O/RB

Driver
79

Tasks/Company

Arrive on Scene

- Arrive/ stop at hydrant

- Position engine

______________

- Layout report

- On-scene report

- Conduct size-up – 360o

lap – incident action plan – offensive

– detail incident (situation report)

- Transmit size-up to responding units

- Transfer command to chief

Establish Supply line

- Hydrant-Drop line (wrap)

- Position engine

- Pump engaged

- 4” straight lay

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

- Supply attack engine (1 3/4”)

Position attack line

- Flake

- Charge

- Bleed

- Advance

Establish - 2 in – 2 out

(Initial RIT)

Establish RIT

(Dedicated)

Company Protocols: Crew Size of 4

Total on scene = 18

PLUS 4 RIC – 1403 = total 22 needed

Engine 1/4

Driver

Officer

-

Driver

Driver

Driver

RB/Nozzle

LB/Flake

Both advance line

for fire attack

Truck 1/4

-Arrive

- 360 degree lap

Position Truck

D/LB

Engine 2/4

-Dry Lay – 2nd

engine takes

hydrant

Charged

hydrant –

Supply attack

engine

Driver

O/LB/RB—

advance by foot

to get to point of

entry – performs

all RIT duties

Battalion Chief/ Aide

- Arrives

- Assumes Command

- Evaluates Resources

- Establishes

Command post

- Evaluates exposure

problems

- Directs hose

positioning

- Coordinates Units

- Transmits

Progress reports

- Changes strategy

- Orders, records, and

transmits results of

primary and

secondary searches

- Declares fire under

control

Engine 3/4
80

Tasks/Company

Gain/ Force Entry

Advance Line

- scan search fire room

- suppression

Deploy Back-up Line and

protect stairwell

Complete Primary Search

(in combo with Fire Attack)

Search Fire Floor

Search other Floors

Ventilation

- Horizontal

- Ventilation

Ground Laddering – 2nd story

windows, front and side, for

firefighter means of egress and for

vertical ventilation – 24’/28’ and

roof ladder in case of vertical vent.

Control Utilities

(Interior and exterior)

Conduct Secondary Search

- Search Fire Floors

- Search other Floors

Check for Fire Extension

Open ceiling walls near fire on fire

floor

Check floor above for fire

extension

- wall breech

- ceiling breech

Mechanical Ventilation

Engine 1/4

RB/LB

Officer – not on line

(if officer commits

then he must pass

command)

O/RB

Truck 1/4

O/RB

Officer and RB

-

Driver and LB

Driver /LB

Driver/LB

(control exterior)

O/RB

(control interior)

O/RB

D/LB

Battalion Chief/ Aide Engine 3/4

O/RB

D/LB
81

Tasks/Company

Arrive on Scene

- Arrive/ stop at hydrant

- Position engine

______________

- Layout report

- On-scene report

- Locate Fire

- Conduct size-up – 360o

lap – incident action plan – offensive

– detail incident (situation report)

- Transmit size-up to responding units

- Transfer command to chief

Establish Supply line

- Hydrant-Drop line (wrap)

- Position engine

- Pump engaged

- 4” straight lay

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

- Supply attack engine (1 3/4”)

Position attack line

- Flake

- Charge

- Bleed

- Advance

Establish - 2 in – 2 out

(Initial RIT)

Company Protocols: Crew Size of 5

D/O/LB/RB/CB Total on scene = 22

PLUS 4 RIC – 1403 = total 26 needed

Engine 1/5

Driver

Officer

-

Driver

Driver

Driver

RB/Nozzle

LB/Flake

CB/ Control

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

Advance line for

fire attack

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

The Officer

responsibility is

to supervise hose

stretch /monitor

safety and

continually survey

the scene

Truck 1/5

-Arrive

- 360 degree

Size up.

Position Truck

D/LB

Engine 2/5

-Dry Lay – 2nd

engine takes

hydrant

Charged

hydrant –

Supply attack

engine

Driver

Battalion Chief/ Aide

- Arrives

- Assumes Command

- Evaluates Resources

- Establishes

Command post

- Evaluates exposure

problems

- Directs hose

positioning

- Coordinates Units

- Transmits

Progress reports

- Changes strategy

- Orders, records, and

transmits results of

primary and

secondary searches

- Declares fire under

control

Engine 3/4
82

Tasks/Company

Establish RIT

(Dedicated)

Gain/ Force Entry

Advance Line

- scan search fire room

- suppression

Insures first line flowing water—

Deploy Back-up Line and protect

stairwell (1 3⁄4”)

Complete Primary Search

(in combo with Fire Attack)

Search Fire Floor –

Search other floorsVentilation (vent forfire or vent forlife)

- Horizontal

- Vertical

Ground Laddering – 2nd story

windows, front and side, for

firefighter means of egress and for

vertical ventilation – 24’/28’ and roof

ladder in case of vertical vent.

Control Utilities after search, force

entry, venting and fire extinguished

(Interior and exterior)

Conduct Secondary Search

-Fire Floor

-Primary and secondary search of

entire floor above

Check for Fire Extension

Open ceiling walls near fire on fire

floor

Check floor above for fire

extension

wall breech

ceiling breechMechanical Ventilation

Engine 1/5

RB/LB/CB

Officer – not on

line (if officer

commits then he

must pass

command)

O/RB

Truck 1/5

O/RB/CB

Officer and

RB/CB

Driver and LB

Driver /LB

Driver/LB

(control exterior)

O/RB/CB

(control interior)

D/LB

Engine 2/5

O/LB/RB—

advance by foot

to get to point

of entry –

performs all

RIT duties

Battalion Chief/ Aide Engine 3/5

O/RB/CB

D/LB

O/RB/CB

O/RB/CB
8

3

Appendix E: Statistical Analysis of Time to Task Test DataIdentifying Statistically Significant Differences in Crew Size and Stagger on a Number of Task Timings Using Regression Analyses of Times (Start, End and Duration) on Crew Size and Stagger
84

Appendix F: All Regression Coefficients

Regression Models of Time to Task (in Seconds) as a Function of Crew Size and Stagger

(Standard Errors are in Parentheses underneath coefficients)
85

All Regression Coefficients (CONTINUED)

Regression Models of Time to Task (in Seconds) as a Function of Crew Size and Stagger

(Standard Errors are in Parentheses underneath coefficients)
86

Regression Models of Time to Task (in Seconds) as a Function of Combined Crew Size and

Stagger (Standard Errors appear in Parentheses)
87

Regression Models of Time to Task (in Seconds) as a Function of Combined Crew Size and

Stagger (CONTINUED) (Standard Errors appear in Parentheses)
88

The measurements of length, temperature, mass, moisture

content, smoke obscuration, and time taken in these

experiments have unique components of uncertainty that

must be evaluated in order to determine the fidelity of the data.

These components of uncertainty can be grouped into two

categories: Type A and Type B. Type A uncertainties are those

evaluated by statistical methods, such as calculating the standard

deviation of the mean of a set of measurements. Type B

uncertainties are based on scientific judgment using all available

and relevant information. Using relevant information, the upper

and lower limits of the expected value are estimated so that the

probability that the measurement falls within these limits is

essentially 100 %.After all the component uncertainties of a

measurement have been identified and evaluated it is necessary to

use them to compute the combined standard uncertainty using the

law of propagation of uncertainty (the “root sum of squares”).

Although this expresses the uncertainty of a given measurement, it

is more useful in a fire model validation exercise to define an

interval for which the measurement will fall within a certain level of

statistical confidence. This is known as the expanded uncertainty.

The current international practice is to multiply the combined

standard uncertainty by a factor of two (k=2), giving a confidence

of 95 %.

Length measurements of room dimensions, openings and

instrument locations were taken using a steel measuring tape with a

resolution of 0.02 in (0.5 mm). However, measurement error due to

uneven and unlevel surfaces results in an estimated uncertainty of ±

0.5 % for length measurements taken on the scale of room

dimensions. The estimated total expanded uncertainty for length

measurements is ± 1.0 %.

The standard uncertainty of the thermocouple wire itself is 1.1°C

or 0.4 % of the measured value, whichever is greater (Omega 2004).

The estimated total expanded uncertainty associated with type K

thermocouples is approximately ± 15 %. Previous work done at

NIST has shown that the uncertainty of the environment

surrounding thermocouples in a full-scale fire experiment has a

significantly greater uncertainty (Blevins 1999) than the

uncertainty inherent with thermocouple design. Furthermore,

while a vertical thermocouple array gives a good approximation of

the temperature gradient with respect to height, temperatures

cannot be expected to be uniform across a plane at any height

because of the dynamic environment in a compartment fire.

Inaccuracies of thermocouple measurements in a fire environment

can be caused by:

 Radiative heating or cooling of the thermocouple bead

 Soot deposition on the thermocouple bead which change its

mass, emissivity, and thermal conductivity

 Heat conduction along thermocouple wires

 Flow velocity over the thermocouple bead

To reduce these effects, particularly radiative heating and cooling,

thermocouples with smaller diameter beads were chosen. This is

particularly important for thermocouples below the interface

because the radiative transfer between the surrounding room

surfaces will be significantly less uniform than if the thermocouple

were in the hot gas layer. It is suggested in [Pitts] that it may be

possible to correct for radiative transfer given enough sufficient

knowledge about thermocouple properties and the environment.

However, measurements of local velocity and the radiative

environment were not taken.Additionally, the probes were located

away from the burn compartment walls in order to avoid the effects

of walls and corners.

The gas measurement instruments and sampling system used in

this series of experiments have been demonstrated to have an

expanded (k = 2) relative uncertainty of ± 1 % when compared

with span gas volume fractions (Matheson). Given the limited set of

sampling points in these experiments, an estimated uncertainty of

± 10 % is being applied to the results.

The potential for soot deposition on the face of the water-cooled

total heat flux gauges contributes significant uncertainty to the heat

flux measurements. Calibration of heat flux gauges was completed

at lower fluxes and then extrapolated to higher values and this

resulted in a higher uncertainty in the flux measurement.

Combining all of component uncertainties for total heat flux

resulted in a total expanded uncertainty of -24 % to +13 % for the

flux measurements.

Prior to experimentation, ten of the wooden pallets used in the

fuel packages were randomly selected for measurement. Two

measurements were taken, moisture content and mass. Moisture

content was measured using a pin-type moisture meter with a

moisture measurement range of 6 % to 40% and an accuracy of

<0.5 % of the measured value between 6 % and 12 % moisture

content. Mass measurements were made with an industrial bench

scale having a range of 0kg to 100 kg, a resolution of 0.1 kg and an

uncertainty of ± 0.1 kg.

All timing staff were equipped with the same model of digital

stopwatch with a resolution of 0.01 seconds and an uncertainty of ±

3 seconds per 24 hours; the uncertainty of the timing mechanism in

the stopwatches is small enough over the duration of an experiment

that it can be neglected. There are three components of uncertainty

when using people to time fire fighting tasks. First, timers may have

a bias depending on whether they record the time in anticipation

of, or reaction to an event. A second component exists because

multiple timers were used to record all tasks. The third component

is the mode of the stimulus to which the staff is reacting: audible

(firefighters announcing task updates over the radio) or visual

(timing staff sees a task start or stop).

Milestone events in these experiments were recorded both audibly

and visually. A test series described in the NIST Recommended

Practice Guide for Stopwatch and Timer Calibrations found the

reaction times for the two modes of stimulus to be approximately

the same, so this component can be neglected. Because of the lack

of knowledge regarding the mean bias of the timers, a rectangular

distribution was assumed and the worst case reaction time bias of

120 ms was used, giving a standard deviation of 69 ms. The

standard deviation of the reaction time was assumed to be the

worst case of 230 ms. The estimated total expanded uncertainty of

task times measured in these experiments is 240 ms.

An additional component of uncertainty exists for the time

measurement of the application of water on the fire. In order to

measure this time, timing staff were required to listen for radio

confirmation that suppressing water had been applied by the

interior attack crew. This process required a member of the interior

crew to find and manipulate their microphone, wait for the radio to

access a repeater, and transmit the message. Because of the lack of

APPENDIX G: Measurement Uncertainty
89

knowledge about the distributions of time it takes for each part of

this process, all parts are lumped into a single estimate of

uncertainty and a rectangular distribution is assumed. This is most

reasonably estimated to be 2.5 seconds with a standard deviation of

±2.89 seconds and an expanded uncertainty of ± 5.78 seconds.

Weather measurement uncertainty was referenced to the

published user’s manual for the instrumentation used. The weather

instrumentation has calibration certificates that are traceable to

NIST standards. A summary of experimental measurement

uncertainty is given in Table G-1.

Table G-1: Summary of Measurement Uncertainty
90

APPENDIX H: Charts of Gas and Temperature Data

Examples of Gas and Temperature Data for Time-to-Task Tests

Burn Room Data
91

Target Room Data
92

Temperature Near Front Door (Couch )
93

Gas and Temperature Data for Room and Contents Tests

Examples of Gas Data in Target Room
94

Gas and Temperature Data for Room and Contents Tests

Examples of Gas Data in Target Room
95

Temperatures in Burn Room
96

Temperatures in Target Room
97

Temperatures Near Front Door (Couch)
98
99

NOTES:

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