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fS^!23’ structure ol OCtOO U5« NO 85-3298 V1986 C.1 NBS-PUB- -3298

The Basic Structure of the Fire

Protection Design Assessment

System

Harold E. Nelson

William D. Walton

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

February 1 986

-QC

100

.056

85-3298

1986

in part by the:

tales Air Force

Vir Force Base, Florida

NBSIR 85-3298

THE BASIC STRUCTURE OF THE FIRE

PROTECTION DESIGN ASSESSMENT

SYSTEM

KBS RESEA2CH unrOHMATION CENTES

1

-

Harold E. Nelson

William D. Walton

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

February 1986

Supported in part by the:

United States Air Force

Tyndall Air Force Base, Florida

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director
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TABLE OF CONTENTS

Page

LIST OF FIGURES iv

Abatract ........ 1

1. INTRODUCTION 2

2. FUNDAMENTAL ASSUMPTIONS 4

3. SYSTEM ORGANIZATION 5

3.1 Building Daba 7

3.1.1 Archibecbural ........ 7

3.1.2 Fuel Packages (Combustible Contents) ... 8

3.1.3 Structural Fire Resistance 9

3.1.4 Detection Equipment 9

3.1.5 Sprinklers 10

3.1.6 Smoke Control . 10

3.1.7 Occupants 11

3.2 Fire Safety Objectives 12

3.3 Computations 14

3.4 Results 15

3.5 Alternative Approaches 16

4. SYSTEM IMPLEMENTATION 16

iii
LIST OF FIGURES

Page

Figure 1. Fire Protection Design Assessment System - General Model Id

Figure 2. Building Data Element 19

Figure 3. Fire Safety Objectives Element 22

Figure 4. Results Element 24

iv
THE BASIC STRUCTURE OF THE FIRE PROTECTION

DESIGN ASSESSMENT SYSTEM

Harold E. Nelson

William D. Walton

ABSTRACT

The purpose of the Fire Protection Design Assessment System is

provide design engineers with a tool to improve their ability to

appraise the overall fire safety in a facility and evaluate the

impact of fire protection measures. The system is based on

deterministic fire prediction techniques and will be implemented

through an interactive computer program. This report describes

the components and basic structure of the system. The inputs to

the system include data on the building layout, combustible

contents, fire resistance, detectors, sprinklers, smoke control

system, occupants and the fire safety objectives. The outputs

include the predicted fire generated conditions within the

building as a function of time and an evaluation of the user

specified fire safety objectives.

Key Words: compartment fires; computer programs; fire growth;

hazard analysis; life safety; mathematical models; room fires;

smoke; toxicity.

1
1 INTRODUCTION

The design of fire safety for buildings has traditionally been

accomplished through the use of building and fire codes. While

this method of design has provided for an "adequate" level of

fire safety in most instances it has at least one ma^or

weakness. It does not permit the engineer to design the building

for a specified level of fire performance under a given set of

fire conditions. Building and fire codes assume that the fire

threat and the desired fire performance will be the same for all

buildings of a similar type and with similar contents and use.

The code approach does not, for example, take into consideration

factors such as the importance of the facility. Therefore, the

code approach may result in over design or under design,

depending on the circumstances. More importantly, the specific

level of fire safety is unknown.

The purpose of the Fire Protection Design Assessment System is to

provide design engineers with a tool to improve their ability to

appraise the overall fire safety in a building or special purpose

facility and evaluate the impact of special fire protection

measures

In structural design, the complete building is considered.

Design is based on code prescribed load values (gravity.

2
earthquake, wind) according to geographical location. In this

"deterministic" fire safety design system, the designer is being

given the opportunity to assume loads, i.e. combustible contents,

rate of burning, combustion products, etc., and to examine

localized fire effects.

The Fire Protection Design Assessment System provides a means to

evaluate scenarios involving different spaces and different

conditions in a given apace. It is based on the prescribed

release of energy and products of combustion and the resultant

flow of heat and mass according to established principles and

data from laboratory fire experiments. The system guides the

user through the process. The user must, however, designate the

room and item of origin and the physical situation he wishes to

analyze, (eg: A fire starting on the bed in a bedroom; comparing

the value of sprinklers, detectors, door closers, and wall fire

ratings .

)

The system consists of a modular computer program. The initial

version of the system limits user choices to a selection of the

fire scenario and the type of output desired. As the system

matures, it will allow the user to select alternate calculation

procedures to evaluate the fire phenomena. The choice will

depend on the computer resources available, the type of problem

to be analyzed and the output desired.

3
2. FUNDAMENTAL ASSUMPTIONS

The design assessment system is based primarily on physical and

chemical relationships governing the growth of fire and its

impact on the structure, contents and occupants • These

relationships have been drawn from the ongoing research at the

Center for Fire Research and other research and engineering

organizations in the U.S. and abroad. They represent the

state-of-the-art in fire prediction for engineering assessment.

In general, the available fire prediction techniques focus on

only one aspect of fire phenomena. This evaluation system blend

a number of these prediction techniques into a uniform and

consistent package. In a number of cases the results from one

prediction are used as input to another.

The main component of the system is a zone fire model. This

model predicts the fundamental properties of the fire generated

environment such as the temperature and location of the hot

gases. This model requires the solution of a set of simultaneous

differential equations. In addition to the base fire model, a number of supplemental calculations requiring the solution of

algebraic equations are performed. The calculations provide items

such as heat flux from the fire and the movement of people.

4
The system divides any story of a building into four segments.

These are:

1. The room of fire origin (actual or design assumed).

2. The entirety of the ad 3 acent room, rooms or spaces open

to the room of fire origin.

3. Rooms, spaces or floors separated from the either of the

two preceding segments by barriers that restrict the flow of

heat, smoke and hot gases.

4. The space outside the building.

The system assumes there are no large unprotected vertical

openings (eg: open stairs, atria, shafts) in the facility and

that leakage from the fire area or nearby smoke laden spaces is

through the spaces around closed doors or other small leakage

spaces. This assumption makes it possible to assess the pressure

required for smoke control.

3. SYSTEM ORGANIZATION

The design assessment system can be broken down into five major

elements. These elements are Building Data, Fire Safety

5
Objectives, Computations, Results and Alternative Approaches. A

schematic showing the organization of these elements is shown in

Figure 1.

The first two, the Building Data and Fire Safety Objectives

elements are the data input section of the system. The system is

designed to be interactive, that is the user will be prompted

with questions concerning the input. The next element.

Computations, is the computational heart of the method. This

consists of the assembled, coordinated set of models, formulas,

and data for making the design assessment. The fourth element.

Results, is the output section of the system. The user may

select from several different output formats depending on the

type of assessment desired. The last element. Alternative

Approaches, assists the user if he desires to appraise

alternative fire safety arrangements.

Although the system is interactive in nature, it has the

capability of generating and reading data files. The user may

select to save the system inputs which were entered interactively

in a computer file for use at a later time. Previously created

data files may be used intact or modified by the user.

A detailed discussion of each of the element is provided below.

6
3.1 Building Data

The Building Data element contains the description of the

facility and its occupancy. The user provides data on the layout

and construction of the facility and the fire protection

systems. The user may elect to evaluate the impact of changes in

arrangement^ materials, use, protection, or occupants.

A modular system for fire safety design or management is being

used. The modules are Architectural, Fuel Package, Structural

Capabilities, Detection Equipment, Sprinklers, Smoke Control, and

Occupants. A diagram of the organization of the Building Data

element is presented in Figure 2.

The contents of the Building Data modules are:

3.1.1 Architectural

This module contains the dimensions (height, length, width),

openings (windows, doors), and leaks (cracks around closed doors,

pokethroughs ) . It also contains the property data for the

building materials (ceiling, walls, floor) . Data on common

materials (concrete, gypsum board, wood, etc.) are Included in

the program and the user need only enter the generic name.

7
The Building Data element consist of separate entries for the

room of fire origin and those spaces open to that room. The

initial version of the system treats the adjacent spaces as a

single combined area.

3.1.2 Fuel Packages (Combustible Contents)

The system assumes that the fire exists only in the room of fire

origin. The system requires that the fuel packages be described

in terms of their rate of heat release. This heat release data

may be obtained from fire teat data or a fire description

formula. Some common fuel packages will be included in the

system and can be specified by name.

In addition to the rate of heat release the user may provide the

rate of production of other fire products such as smoke

particulate mass or CO. The concentration of these products in

the building spaces will be calculated during the fire.

As shown in figure 2 , the Building Data element can accommodate

descriptive information on the first ignited fuel package,

several exposed fuel packages, and the total fuel in the room of

fire origin. In addition to the heat release data, the height

above the floor of the top surface of the first fuel ignited

package is required. Where separate fuel packages are involved

the distances between the packages must be given.

a
3.1.3 Structural Fire Resistance

The Structural Fire Resistance module contains the data necessary

/ to compute the duration of the fire and the effective fire

resistance required of building assemblies to withstand a

complete burn-out of the fire room. The effective fire

resistance will be compared to the rated fire resistance of the

building assemblies. The data includes the combustible fuel load

in the room, the size of the room and openings to the room, and

the rated fire resistance of the building assemblies bounding the

room

3.1.4 Detection Equipment

The Detection Equipment module contains information on thermal

and/or smoke detectors located in the room of fire origin. The

system assumes that the detectors are at or near the ceiling

level. The required data are the lateral distance (actual or

maximum potential) from the fire to the detector and the

proximity of the detector to a wall. For heat actuated

detectors, the activation temperature and the response time index

(RTI) or other sensitivity data (such as the UL listed spacing)

is needed.

9
3.1.5 Sprinklers

The Sprinkler module treats sprinklers in the same manner as heat

actuated detectors. The data required are the location of each

sprinkler head with respect to the fire and the walla, the

activation temperature and RTI value.

3.1.6 Smoke Control

The system provides smoke control evaluations in the form of:

a. The rate and total amount of leakage of fire products

through small openings (eg: the cracks around closed doors,

small transfer grills, pipe chases, pokethrougha .

)

b. The rate of smoke removal and the impact of such on the

accumulation of smoke in the vented space.

c. Critical counter pressures needed to prevent smoke

passage through a crack.

Much of the data required is taken from the architectural

module. The user must identify the barrier(s) of concern in

terms of size and location of the leakage openings. For smoke

venting calculations the size of the vents (or capacity, if

powered), the means for initiating the opening of the vents (or

10
starting if powered) and the size (or capacity) of low level air

intakes are required. To determine if the building HVAC or smoke

control system will prevent smoke flow through cracks, the

pressure differential between compartments developed by the HVAC

or smoke control system must be given.

3.1.7 Occupants

The Occupants nodule assembles the data needed to estimate the

time required for egress. The system does not calculate the

start up tine between the moment of awareness (alarm or other

fire cue) and the instant the actual evacuation movement starts.

The system allows the user to make an estimate of this tine or

the system can compute the time available for start up

activities. The user enters the number of occupants in:

a. The room of fire origin.

b. Those spaces open to that room.

c. Other spaces using the same exit routes as persons in the

other two spaces.

The occupants are graded by overall capabilities (able or

handicapped) and condition (awake, asleep, etc.). The user must

enter the number of occupants involved, the maximum travel

11
distances, the extent of vertical (stair) travel and the number

and sizes of doors available for egress.

3.2 Fire Safety Objectives

The Fire Safety Objectives element allows the user to control the

manner and criteria of fire safety evaluation. This element

permits the user to examine selected conditions or events and/or

set specific levels of performance or design limits. A diagram

of the organization of the Fire Safety Objectives element is

presented in Figure 3.

The user may examine conditions or time to events from the

following list:

1. Upper (smoke) layer temperature

2. Depth of smoke layer

3. Smoke layer characteristics (eg: visibility, toxicity)

4. Thermal radiation from the fire

5. Time to flashover

6. Fire duration

7. Time to exceed fire resistance rating of a building

assembly

8. Detector activation

9. Sprinkler activation

12
10. Smoke leakage

11. Evacuation time required

The user may elect to set design limits in the following areas:

1 . Human tolerances

a . Heated gas temperature

b. Thermal radiation from heated gases and surfaces

c. Optical density of smoke

d. Toxic concentrations and dosages

2. Building assembly tolerances

a. Fire resistance

b. Smoke transmission

3. Contents tolerances

a. Exposure to heated gases

b. Thermal radiation from heated gases and surfaces

c. Chemical exposure

The user may select any or all of the above and may use the

suggested values or modify them to meet specific needs.

In addition the user may have the method measure the "Margin of

Safety" between the time require for egress and the onset of

conditions intolerable to humans.

13
3.3 Comput.at.iona

As previously mentioned, the main computational component of the

system is a zone fire model. ASET (Available Safe Egress Time) a

zone fire model written by L. Y. Cooper at the Center for Fire

Research has been selected as the base model. The design

assessment system utilizes the basic physics contained in the

ASET model and utilizes significant enhancements to meet the

ob 3 ecta of the system. Since the system is modular, the base

model can be changed as more sophisticated models and more

powerful computers become available.

The Fire Protection Design Assessment System addresses a number

of areas which are not addressed by the present zone fire

models. In order to accommodate these areas two approaches have

been taken. The first is the addition of computational routines

which will be called directly by the base model. The primary

output of the zone fire model is the depth and temperature of the

hot smoke layer. The depth and temperature as a function of time

are determined by solving the appropriate equations over a series

of small time intervals. In order to determine other parameters

as a function of time the equations must be solved over the same

series of time intervals. Examples of parameters which must be

solved as a function of time are smoke layer constituency, time

to flashover, detector and sprinkler activation, smoke leakage

and evacuation time.

14
A second method of adding areas not addressed by the baseline

zone fire model is the use of independent calculations. These

are calculations which are not explicitly a function of time,

however they may require as input the results of the time

dependent calculations. An example of an independent calculation

is effective fire resistance.

3.4 Results

The results provided by the system consist primarily of those

items selected in the Fire Safety Objectives element. If the

user has selected specific conditions to be examined they will be

presented in tabular form as a function of time. If the time to

events or design limits have been selected, the system will

report each of the events or limits and the time required to

reach it. A diagram of the organization of the Results element

is presented in Figure 4.

Provisions will be included for the graphical presentation of the

results. Since computer graphics are dependent on the computer

and its peripherals the exact form of the graphical output has

not been determined.

15
3.5 Alternative Approaches

The design assessment system la primarily a deterministic system

and la not intended to be an expert system. There are however

some simple rules which can be used to evaluate the results and

provide the user with a systematic means of evaluating

alternatives

If the predicted performance of the facility is deemed

unsatisfactory, the user may wish to examine alternative

approaches. Unsatisfactory performance may occur for example,

when the time required for egress is greater than the time for

the onset of hazardous conditions. Upon determining that the

performance is unsatisfactory the user may request a list of

potential alternative approaches. This list will correspond

closely to the building data modules in section 3.1. From this

list the user can select approaches which are potentially viable

for the facility being examined. The system will then apply some

simple rules to select the most promising approaches. Since the

models used to predict fire performance can not in general be

solved in reverse, the system will have to be rerun to examine

the effect of the alternative approaches.

16
4. SYSTEM IMPLEMENTATION

This paper has presented the capabilities and the basic structure

of the Fire Protection Design Assessment System. The primary

relationships describing the physical processes and algorithms

for their implementation have been developed. The development of

a computer program which implements the system in stages is

underway. At the end of each stage the program will be evaluated

for usability and the results will be compared with available

full scale fire test data. The completed program will undergo

field evaluation before final release and will include program

documentation as well as a user's guide.

17
FIRE PROTECTION DESIGN ASSESSMENT SYSTEM

Figura 1. Fira Protactlon Daaign Aaaaaamant Syatam

Ganeral Model

Id
Figure 2. Building Data Element

19
BUILDING DATA MODULES

ARCHITECTURAL DATA

ROOM OF ORIGIN

DIMENSIONS

MATERIALS

OPENINGS

LEAKS

ADJOINING SPACE(S)

DIMENSIONS

MATERIALS

OPENINGS

LEAKS

FUEL PACKAGE DATA

FIRST IGNITED

RATE OF:

ENERGY PRODUCTION

MATERIAL DESTRUCTION

PRODUCT <S) PRODUCTION

LOCATION

EXPOSED FUEL PACKAGES

BURNING RATES

IGNITION SUSCEPTIBILITY

LOCATION

TOTAL FUEL (ROOM OF ORIGIN)

MASS AVAILABLE

PYROLYSIS RATE

STRUCTURAL FIRE RESISTANCE

COMBUSTIBLE FUEL LOAD

RATED FIRE RESISTANCE OF BUILDING ASSEMBLIES

Figure 2. (continued) Building Det.a Element.
BUILDING DATA MODULES

DETECTION EQUIPMENT

ROOM OF ORIGIN

SMOKE

LOCATION

HEAT

POSITION

RESPONSE TIME

ACTIVATION TEMPERATURE

SPRINKLERS

ROOM OF ORIGIN

LOCATION

RESPONSE TIME INDEX

ACTIVATION TEMPERATURE

SMOKE CONTROL

VENTS

SIZE (CAPACITY)

LOCATION

INITIATION METHOD

HVAC OR SMOKE CONTROL SYSTEM

PRESSURE DIFFERENTIAL

INITIATION METHOD

OCCUPANTS

NUMBER OF OCCUPANTS

CAPABILITIES

CONDITION (AWAKE, ASLEEP, ETC.)

MAXIMUM TRAVEL DISTANCE

DOORS

STAIRS

Figure 2. (continued) Building Data Element

21
Figure 3. Fire Safety Objectivea Element

22
CONDITIONS OR EVENTS FOR EXAMINATION

SMOKE LAYER TEMPERATURE

SMOKE LAYER LOCATION

SMOKE CONSTITUENCY

OPTICAL DENSITY

TOXIC CONCENTRATION

TIME TO FLASHOVER

FIRE DURATION

FIRE RESISTANCE OF A BUILDING ASSEMBLY

DETECTOR ACTIVATION

SPRINKLER ACTIVATION

SMOKE LEAKAGE

EVACUATION TIME

i DESIGN LIMITS

HUMAN TOLERANCES

HEATED GAS TEMPERATURE

THERMAL RADIATION

SMOKE OPTICAL DENSITY

SMOKE TOXICITY

BUILDING ASSEMBLY TOLERANCES

FIRE RESISTANCE

SMOKE TRANSMISSION

CONTENTS TOLERANCES

HEATED GAS TEMPERATURE

THERMAL RADIATION

* CHEMICAL EXPOSURE

i SAFETY MARGIN

TIME AVAILABLE FOR EGRESS

i TIME TO UNTENABLE CONDITIONS/TIME REQUIRED FOR EGRESS

Figure 3. (continued) Fire Safety Objectives Element

23
Figure 4. Results Element

24
NBS-114A (REV. 2-80) U.S. OEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET fSee instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR-85/3298

2. Performing Organ. Report No 3. Publication Date February 1986

4, TITLE AND SUBTITLE

The Basic Structure of the Fire Protection Design Assessment System

5. AUTHOR(S)

Harold E. Nelson and William D. Walton

6. PERFORMING ORGANIZATION (if joint or other than NBS, see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

United States Air Force

Tyndall Air Force Base, Florida

10.

SUPPLEMENTARY NOTES

I I Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

The purpose of the Fire Protection Design Assessment System is to provide design

engineers with a tool to improve their ability to appraise the overall fire safety

in a facility and evaluate the impact of fire protection measures. The system is

based on deterministic fire prediction techniques and will be implemented through

an interactive computer program. This report describes the components and basic

structure of the system. The inputs to system include data on the building layout,

combustible contents, fire resistance, detectors, sprinklers, smoke control system,

occupants and the fire safety objectives. The outputs include the predicted

fire generated conditions within the building as a function of time and an evaluation

of the user specified fire safety objectives.

12.

KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key wcis by semicolons)

Compartment fires; computer programs; fire growth; hazard analysis; life safety;

mathematical models; room fires; smoke; toxicity

13. AVAILABILITY

{T~] Unlimited

I I For Official Distribution. Do Not Release to NTIS

I I Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

29

15. Price

$9.95

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