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Nelson, Harold E/A qualitative analysis QC100 .1156 NO.86-3502 1986 V19 C.1 NBS-P

J

A Qualitative Analysis of the

Inherent Fire Safety/Fire Risk in A

Coal Mine

Harold E. Nelson

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

December 1986

-QC - 100

. U56

86-3502

1986

c.2

sored in part by:

Department of Interior

;au of Mines

burgh, PA

MBS

RESEARCH

INFORMATION CENTER NBSIR 86-3502

Qi*(oo

A QUALITATIVE ANALYSIS OF THE

INHERENT FIRE SAFETY/FIRE RISK IN A

COAL MINE

Harold E. Nelson

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

December 1986

Sponsored in part by:

U.S. Department of Interior

Bureau of Mines

Pittsburgh, PA

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

TABLE OF CONTENTS

Page

CHAPTER 1 . GENERAL 1

CHAPTER 2. EVENT LOGIC TREE APPROACH 1

CHAPTER 3. GENERAL EVENT LOGIC TREE 4

1.0 Fire Safety Performance 5 2.1 Prevention of a Fire Initiation 5 3.1 Manage Fuel Ignitability 6

4.1 Control Fuel Availability 6 4.2 Control Fuel Susceptibility 6 3.2 Limit Igniters 7 12.1 Control Impact 7 13.1 Threat Control 8 14.1 Control Threat Produced by Fire Energy 8 15.1 Limit Inherent Potential 8 15.2 Control by Intervention 9 14.2 Control Mass Products Threat 9 14.3 Control Other Fire Induced Threats 9 23 .

1

Protect "Exposed" 10

24.1 Limit or Exclude "Exposed" 10

24.2 Safeguard "Exposed" from Given Threat 10

CHAPTER 4. CONTROL FUEL AVAILABILITY BRANCH 11

4.1 Control Fuel Availability 11

5.1 Control Entry 11

5 . 2 Remove 11

6.1 Exhaust 12

6 . 2 De-gas 12

6.3 Clean 12

6 . 4 Other 12

5.3 Control of Availability of Fuel Present 12

6.5 Limit Increases in Availability of the Fuel 13

6.6 Reduction of the Availability of a Fuel (i.e., Control

Fuel Exposure) 13

CHAPTER 5. CONTROL FUEL SUSCEPTIBILITY BRANCH

4.2 Control Fuel Susceptibility 14

5.4 Maintain Environment Outside Combustible Limits

of Fuel 14

6.7 Develop Fuel Rich Environment 15

6.8 Develop Fuel Lean Environment 15

5.5 Control Temperature Dependent Susceptibility 15

6.9 Manage Critical Temperature of Fuel 16

6.10 Maintain Surface Temperature Below Critical Level 16

7.1 Reduce Surface Temperature of Fuel Below Critical

Temperature 17

iii
7.2 Prevent Temperature Rise of Fuel 17

8.1 Interpose Energy Transfer Barrier Between Energy

Source and Fuel 17

8.2 Control Response to Incident Energy 18

9.1 Incident Energy 18

9.2 Resistance to Energy Impact 20

CHAPTER 6. LIMIT IGNITERS BRANCH 21

3.2 Limit Igniters 21

4.3 Control "Pilot" Ignition Potential 21

5.6 Prohibit, Limit, Exclude 21

5.7 Other Protection 22

4.4 Control Self (auto) Ignition Potential 22

5.8 Internally Induced Heating Control 23

5.9 Externally Induced Heating Control 23

CHAPTER 7. LIMIT INHERENT POTENTIAL BRANCH 23

15.1 Limit Inherent Potential 24

16.1 Control Extent of Burning Area 24

17.1 Control Surface Flame Spread 24

18.1 Control Material 25

19.1 Control Chemical Response 25

19.2 Control Temperature Rise of Unignited Portions of

Surface 25

20.1 Obstruct Energy Transfer to Surface 26

21.1 Energy Exposure 26

21.2 Effectiveness of Obstructions to Energy Exposure 26

20.2 Control Response to Incident Energy 27

21.3 Incident Energy 27

21.4 Resistance to Energy Impact 27

18.2 Control Level of Energy Exposure to Unignited

Portions of Surface 27

19.3 Control Exposure from Involved Portions 28

19.4 Control Expossure from General Environment 28

17.2 Control Other Means of Extension of Burning Area 28

18.3 Prevent Fire Induced Ignition of Other Fuels 29

18.4 Control Exposure from General Environment 29

16.2 Control Fire Intensity 29

16.3 Control Fire Severity 31

17.3 Control Fire Intensity 31

17.4 Limit Available Fuel Mass 31

CHAPTER 8. CONTROL BY INTERVENTION BRANCH 32

15.2 Control by Intervention 32

16.4 Control by Suppression of Burning 32

17.5 Control by Removal of Fuel Availability 32

17.7 Control by Cooling 33

17.6 Control by Oxygen Deprivation 34

18.5 Replace Oxygen with Inert Gas 35

18.6 Exclude Oxygen by Other Means 35

17.8 Control by Other Means 35

iv
16.5 Control by Confinement of Extent of Burning • 35

17.9 Perimeter Completeness 36

17.10 Provide Structural Endurance 36

18.7 Fire Severity 37

18.8 Structural Endurance Capability 37

17.11 Provide Thermal Endurance 37

18.9 Fire Severity 38

18.10 Thermal Endurance Capability 38

14.2 Control Mass Products Threats 38

15.3 Control Product Production 39

16.6 Fire Energy Threat 39

16.7 Products Produced 39

15.4 Manage Product Movement 40

16.8 Control Movement Energy 40

17.12 Control Fire Induced Energy (Buoyancy) 40

18.11 Control by Adding Cooling Agents 40

18.12 Control by Transfer to Other Masses 41

17 . 13 Control Other Gas Movement Forces 41

18.13 Control Mechanically Induced Forces 41

18.14 Control Barometric Induced Forces (Stack Effect) 42

18.15 Control Wind Induced and Other Forces 42

16.9 Control Movement 42

17.14 Obstruct Movement with Barriers 42

17.15 Manage Fluid Dynamics 43

18.16 Control by Dilution 43

18.17 Control by Exhaust or Venting 43

18.18 Control with Pressure Differential 44

CHAPTER 10. OTHER FIRE INDUCED THREATS BRANCH 44

14.3 Control Other Fire Induced Threats 44

15.5 Control Oxygen Depletion 44

15.6 Prevent Mine Collapse 45

CHAPTER 11. LIMIT OF EXCLUDE "EXPOSED" BRANCH 45

24.1 Limit or Exclude "Exposed" 45

25.1 Limit Access to the Mine 46

26.1 (Limit Access to Mine) at All Times 46

26.2 (Limit Access to Mine) at All Times of Specific

Conditions, Threats or Potentials 46

25.2 Limit Access or Concentration of "Exposed" in

Specific Areas of Mine 46

26.3 Limit Access or Concentration to Specific Areas

(at all times) 46

26.4 Limit Access or Concentration in Specific Areas at

Times of Specific Conditions, Threats, or Potentials 46

25.3 Evacuate in Case of Potential Threat 47

CHAPTER 12. SAFEGUARDING "EXPOSED" BRANCH 47

24.2 Safeguard "Exposed" from Given Threat 47

25.4 Provide Protection in Place 49

V
26.5 Provide Inherently Safeguarded Place 49

26.6 Threat Initiated Safeguard 49

25.5 Relocate "Exposed" to In-Mine Refuge Areas 50

25.6 Evacuate Mines 51

CHAPTER 13. STATES AND TRANSITIONS 51

Fire Behavior Sequence 53

a. State 0, Non-Burning 53

b. State 1, Development on First Ignited Fuel 55

c. State 2, Multi-Item, Fuel - Controlled Burning 56

d. State 3, Ventilation Controlled Burning 57

e. State 4, Multi - Spacial Involvement 58

f. State 5, Mine Fire 59

Human Behavior Sequenced 59

a. Episode A, No Action 60

b. Episode B, Investigate 60

c. Episode C, Attack 60

d. Episode D, Alarm 61

e. Episode E, Flee/Escape 61

f. Episode F, Rescue 61

General Mode 61

Vi
LIST OF FIGURE

Page

Figure 1. General (overview) Event Logic Tree 63

Figure 2. Control Fuel Availability Branch 64

Figure 3. Control Fuel Susceptibility Branch 65

Figure 4. Limit Igniters Branch 66

Figure 5. Limit Inherent Potential Branch 67

Figure 6. Control by Intervention Branch 68

Figure 7. Mass Product Threat Branch 69

Figure 8. Control Other Fire Threats Branch 70

Figure 9. Limit of Exclude "Exposed" Branch 71

Figure 10. Safeguard "Exposed" from Given Threat Branch 72

Figure 11. Functional Branches A and B 73

Figure 12. Functional Branch C 74

Figure 13. Functional Branches D, E, and F 75

Figure 14. Functional Branches G and H 76

Figure 15. General Model of Interrelationships Between States and

Episodes 77

vii

CHAPTER 1 - GENERAL

This is a report of Phase I of the NBS project, Systems Approach to Mine Fire

Safety, being conducted under sponsorship of the U.S. Bureau of Mines. The

purpose of Phase I was to develop a qualitative description of the inherent

fire safety/fire risk system in a coal mine. The approach consisted of the

development of an event logic tree to analyze forces and countermeasures

involved, and the development of a supporting state transition model to assist

in identifying the states of fire development and human response potentially

occurring in a mine fire.

An event logic tree and a state transition model have been developed. The

development is considered interim as it is expected that additional

information will cause improvements and changes during the subsequent phases

of the project.

The bulk of the report, Chapters 2 through 12, constructs an event logic tree

designed to divide the fire safety methodological factors that determine coal

mine fire safety into related constituent parts. Chapter 13 presents a state

transition model, designed to consider potential levels of fire development in

coal mines

.

CHAPTER 2 - EVENT LOGIC TREE APPROACH

The Event Logic Tree approach used in this study follows the general concepts

of a reliability tree or a reliability network applied in a qualitative form.

The general rules that would apply in a quantitative analysis have been

followed. However, the state-of-the-art of data and the potential of

acquiring new data is such that it is impractical to expect a truly

quantitative tree covering the full breadth undertaken in this exercise. In

each case, however, where quantitative data can be developed or used in part,

the tree is designed to accept it to whatever degree it may be applicable to an internal tree decision or calculation.

1
The tree itself is a diagrammatic means of showing the complete event logic

system that progressively subdivides the problem (analysis of the existent

fire safety/fire risk system in mines) into smaller and smaller elements to

the level at which a rational judgement can be made. The tree arrangement

assists in pointing out events that must occur simultaneously versus those

that can independently control the results. Thereby showing which elements can contribute most effectively to the success of the fire safety system. The

tree also inherently expresses choices or tradeoffs that can be involved in

this performance. The identification of events and the arrangement of gates

in the tree show conditionality and situations where events are mutually

exclusive. In designing the tree, the following general protocol was followed

1. All events were kept consistent in term. In this tree, all events are expressed in terms of success in achieving the fire safety performance

of the top event (Event 1.0, Fire Safety Performance).

2. The universe is maintained throughout the tree so that any lateral cut

through the tree will describe the identical universe to either the top

event or the entirety of the bottom events. This universe is the

universe of success (or contribution) to fire safety performance. In

addition, the universe of the top event is identical to the collection

of all bottom events.

3. At each step, a gate factors the universe of the event above the gate

into the events below the gate.

4. Conditionalities are determined and identified in the gates in the tree

and in the accompanying definitions.

5. The conditionalities are expressed in unit terms, i.e., if the unit

statement is used, a conditional event includes all of its

conditionalities such that it can mathematically function as an independent, collective entity.

2
6. This system is sufficiently dimensionally consistent so that the

dimensions feeding into a gate from sub-events are the same and

consistent with the event being fed.

7 . Each gate can be stated in a mathematical sentence covering all of the

involved events including conditionalities.

8. Each event added to the tree adds understanding and potential for the

intended use of the tree.

The tree progressively factors the initial or "top" event. In this tree, the

top event is entitled, Fire Safety Performance, and is the measured or demanded level of prevention or limitation of harm to persons, property or functional capability. At each step of the factoring, the events necessary to

achieve the higher event are deduced and analyzed to determine if success in

the higher event is dependent upon simultaneous success in all of the factored

events or, conversely, success in any single event. This query determines the

type of gate involved.

Traditionally, event logic trees use only two types of gates "AND" and "OR".

In this tree, however, the category of types of gates has been further

subdivided to show inherent differences "OR" gates. Special symbols have been

developed and used to separate the "OR" gates into three separate categories

as follows:

a. Mutually exclusive "OR" gates (either/or, but not both).

b. Not mutually exclusive "OR" gates (either/or, or both).

c. Multi-variant relationships (i.e., probability density function), where

one event is conditional on both the occurrence and magnitude of the

other event.

In addition, this tree includes an approach referred to as a Function Gate.

The function gate does not actually subdivide the event in probabilistic type

3
elements, but rather is used to lead to a special branch listing physical or behavioral elements that determine the level of performance of an event.

Function gates are always at the termination of a branch of the main tree.

Wherever possible, the branches relate fire phenomena or the response of

people and material to fire impositions to the events in the tree.

Chapters 3 through 12 , and Figures 1 through 14 lay out and analyze the Event

Logic Tree

.

In Chapters 3 through 12,, the tree is analyzed in terms of the definition of

events and the functioning of the gates. For each chapter there is a corresponding figure showing the portion of the tree being analyzed. In some chapters there are also corresponding figures showing functional branches

related to the chapters. In each case, the analysis is made by following the

tree from its top and at each gate moving to the left hand side of the gate.

When an end event is reached in this manner, the sequence proceeds to cover

all connected events, following the lines of connections, while moving from

the left hand side of the page to the right hand side.

CHAPTER 3 - GENERAL EVENT LOGIC TREE (Figure 1)

For ease of handling, the coal mine Event Logic Tree has been divided into a General Event Logic Tree and a series of branches. This chapter covers the

general tree. Each terminal event in the general tree is the top event of one of the separately reported branches.

Each event is identified by an arbitrary numbering system that matches the

numbering system in the Event Logic Tree, followed by the title of the event.

The title matches the wording in the tree. For each event, the principal

element is defined and the gate leading from that event to subsequent events

described

.

4
1.0 Fire Safety Performance

Fire safety performance is the measured or demanded level of prevention or limitation of selected form(s) of harm to persons, property, or functional

capability. The tree can handle all potential forms of harm (either singly or

as a synergistic collection) . The user of the tree or the authority

overseeing its application must, however, declare the specific types of harm

under consideration. The event logic tree is so designed that this event is

reached only if all routes to it are brought to a common measurement of degree

of success in avoidance of harm. In those instances where it is desired to use the tree at a lesser level of sophistication (e.g., probability of

avoidance of harm if fire occurs), some portions of the tree rather than its

total entity should be used.

Gate 1.0 - The degree of success in meeting fire safety performance objectives

is the sum of degree of success in preventing fire initiation plus the degree

of success in controlling the impact of those fires that are initiated. This

gate is a mutually exclusive "OR" gate. In any specific instant, success may

be achieved by preventing fire or controlling it, but not by both.

2.1 Prevention of a Fire Initiation

Fire initiation is the start of the destructive endangering process of

burning. The actual onset of fire initiation may be defined differently by

different users of the tree. It is considered legitimate to define fire

initiation by any of the critical events listed in Chapter 13 as a transition

from State 0 to another state. It is essential, however, that the user of the

tree declare his working definition of the onset of fire initiation and that

this definition be held constant throughout that use of the tree.

Gate 2.1 - The degree of success in prevention of fire initiation is the sum

of the degree to which all potential fuel is managed to keep it in an unignitable condition and the degree to which ignition sources are kept from

any fuel that is in an ignitable condition.

5
3.1

Manage Fuel Ignitabilitv

To be ignitable, a material must be combustible (i.e., a fuel) and be in a condition where the presence of ignition energy in contact with the fuel or volatilized effluent from the fuel bed will result in fire initiation.

Gate 3.1 - The degree of success in managing fuel ignitability is the sum of

the degree that fuel is made unavailable to potential ignition energy sources plus the degree to which that available is prevented from reaching a susceptible condition.

4.1 Control Fuel Availability

A material is considered an available fuel if it is combustible and its

location and character are such that it may exist in, or be brought to an ignitable condition by either normal or emergency environments.

Control fuel availability is the top event of a separate branch. This branch

is covered in Chapter 4.

4.2 Control Fuel Susceptibility

To be susceptible a fuel must be available. An available fuel is susceptible

to ignition if the inherent or situation induced conditions bring the fuel to

a state where the presence of an ignition source can cause the onset of fire.

Since ignition susceptibility applies only to those fuels that are available,

all considerations of degree of success in this event are conditional on the

degree of failure of Event 4.1, Control Fuel Availability.

Control fuel susceptibility is the top event in the branch of the tree covered

in Chapter 5.

6
3.2 Limit Igniters

An igniter is any energy source sufficient to raise the temperature of an ignitable fuel (see Event 3.1) to the transition from a non-burning state to

fire initiation (in accordance with the definition of fire initiation used in

the particular application of the tree)

.

Limit Igniters is a conditional event. Success in this event contributes to

the overall success of the tree only to the extent that such igniters relate

to fuels that are in an ignitable condition (i.e., degree of failure of Event

3.1, Manage Fuel Ignitability)

.

Limit Igniters is the top event of the branch of the tree covered in Chapter

6 .

12.1 Control Impact

Control impact is the top event in one of the two major subdivisions on the

tree. (Prevention of Fire Initiation is the other major subdivision.)

All aspects of the tree relating to any state of burning, except State 0, NonBurning (see Chapter 13), are covered under this event.

Impact is the extent and degree of harm that results if fire is initiated.

Harm is measured in the same terms as the harm element of Event 1.0, Fire

Safety Performance. Control impact is a conditional event dependent on the

failure of Event 2.1, Prevention of Fire Initiation.

Gate 12.1 - The degree of success in controlling the impact of any fire that occurs is the sum of the degree that the fire threat is controlled plus the

degree that the exposed (persons, property, or functional capability) are protected against the residual (uncontrolled amount of) threat.

7
13.1

Threat Control

Threat is the potentially harmful effects of fire as measured at any given

place or moment in the fire. Threat is the combined harmful potential of all

forms of change that are induced by fire, its effects, or the impact of fire

control measures. Included are the combustion zone itself, smoke and heated

or toxic gases, reduction in oxygen, structural collapses and extinguishment

byproducts

.

Gate 13.1 - The degree of success in threat control is the degree of

concurrent control of the threat produced by the fire energy, the threat

imposed by the mass products produced by the fire by itself or in combination

with extinguishing efforts, and the threat from other fire induced conditions

such as, oxygen depletion or roof collapse.

14.1 Control Threat Produced by Fire Energy

The fire energy threat is the fire (combustion reaction) itself and all forms

of threat produced by that combustion and fire caused responses to it.

The degree of success in controlling the threat produced by fire energy is the sum of the degree of success in limiting the inherent potentials (size and

level of energy) plus the degree of success of intervention efforts to stop or limit the development of that potential.

15.1 Limit Inherent Potential

The inherent potential of a fire is defined as the extent of spread of the

combustion process and the resultant energy release, given the lack of

successful intervention efforts to halt, limit, or terminate such potential.

Limit Inherent Potential is the top event of the branch covered in Chapter 7.

8
15.2

Control by Intervention

Intervention is the application of any fixed or "time-of-fire" feature or act

that causes a termination, slowing, or other reduction in the potential fire

energy threat. Intervention impacts on the outcome only to the degree that it

reduces a threat that is not limited or controlled by the Limit Inherent

Potential Branch.

Intervention is the top event in the branch of the tree covered in Chapter 8.

14.2 Control Mass Products Threat

Mass products are defined as the various chemical species and particulate

products generated by the combustion process or by efforts to extinguish or control that process. Mass products also include any air or other gases

entrained into the flow of fire generated products. Mass products include,

but are not limited to, those fire products usually referred to as smoke and

toxic gases

.

Control Mass Products Threat is the top event in the branch of the tree

covered in Chapter 9.

14.3 Control Other Fire Induced Threats

Other Fire Induced Threats is an open-ended term covering both the identified

and potential, yet unidentified threats not covered under the definitions of

Fire Energy or Mass Products. This includes but is not limited to the threats

resulting from fire induced depletion of oxygen, roof or structural collapse,

and pressure fronts produced by a fire induced explosion.

Control of Other Fire Induced Threats is the top event in the branch of the

tree covered in Chapter 10.

9
23.1

Protect "Exposed

Exposed is defined as the persons, property, or capabilities under

consideration. Any specific definition is appropriate but it must be

identical to that which is the objective of Event 1.0, Fire Safety

Performance

.

Gate 23.1 - The degree of success in protecting the "exposed" is the sum of

the degree of success in limiting the quantity of "exposed" plus the degree to

which the number of exposed persons or amount of property, or capacity present

is safeguarded from the degree of threat not controlled by the events covered

under Event 13.1, Threat Control.

24.1 Limit or Exclude "Exposed"

The definition of "Exposed" is as stated in Event 23.1, Protect "Exposed".

Limit or Exclude "Exposed" is the top event in the branch of the tree covered

in Chapter 11.

24.2 Safeguard "Exposed" from Given Threat

The definition of "Exposed" is as stated in Event 23.1, Protect "Exposed".

The degree of "exposed" consists of that which is not excluded or limited by

Event 24.1, Limit or Exclude "Exposed". The threat of concern is the residual

resulting from the degree of failure of Event 13.1, Threat Control.

Safeguard "Exposed" from Given Threat is the top event in the branch of the

tree covered in Chapter 12.

10
CHAPTER 4. - CONTROL FUEL AVAILABILITY BRANCH (Figure 2)

4.1 Control Fuel Availability

A material is an available fuel if it is combustible and its location and

character are such that it may exist in or be brought to an ignitable

condition by either normal or emergency environments.

Gate 4.1 - The degree of success in controlling fuel availability is the

degree to which fuels can be kept from the mine, plus the degree that fuel in

the mine is removed, or is kept in a state or condition that makes it more difficult for environmental conditions to bring it to an ignition susceptible

state

.

5 . 1 Control Entry

Entry of fuel applies to any combustible material brought into the mine for

construction, maintenance, comfort, production, or other reasons. The degree

of success is the degree that such fuel is limited either by prohibition or control of the combustibility of the materials actually used.

This is an End Event in the event logic tree as drawn. The user of the tree

may desire, at his own discretion, to extend this or any other End Event

further into its constituent element if his needs so dictate.

5 . 2 Remove

Removal of fuel covers any action that takes the fuel (gas, liquid, or solid)

from the mine.

Gate 5.2 - The degree of success of removal of fuel is the degree that fuel is

taken from the mine by any means that transports it out of the environment.

11
6.1

Exhaust

Removal of fuel by exhaust is the removal of gases or airborne fuels from the

excavate portions of the mine by exhaust fan or other pressure induced

differentials

.

6.2 De - gas

De-gasing is the removal of methane or other entrapped gases from the

indigenous unmined coal mass prior to mining or excavation operations.

6.3 Clean

Removal by cleaning is the transport of solid or liquid materials that are no longer performing operational or other functions out of the mine. This

includes both materials brought into the mines and the clean-up of any

spillage of product coal that occurs from the mine production, haulage or storage of coal.

6,4

Other

Other is recognition that there can be removal arrangements other than those

defined under Exhaust, De-gas, and Clean.

Events 6.1, 6.2, 6.3, and 6.4 are End Events in the Event Logic Tree as drawn.

5,3 Control of Availability of Fuel Present

The fuel present is all of that indigenous and non- indigenous fuel that is

present in the mine at any instance. It includes both the mined and unmined

coal; entrapped or liberated methane or other material; and all construction,

operational, or other fuels that have been brought into the mine.

Availability is the sum of the physical factors (e.g., particle size,

location, encasements) that determine the degree of exposure of the fuel to

the energy environment.

12
Gate 5.3 - The degree of success in Control of Availability of Fuel Present is

the sum of the degree of success in preventing or limiting increases in

factors that make fuel more available plus the degree to which fuels can be

made less available to influence by energy environments.

6.5 Limit Increases in Availability of the Fuel

Increases in availability are those actions or processes that cause a fuel to

become more available to. influence by energy environments. The energy

environments include all conditions (normal and abnormal) that bring radiated,

convected, or conducted energy to a fuel. The source of the energy may be

from any heat producing condition. Typical examples of design or controllable

activities that influence any increase in the level of availability include:

A. The rate and mode of production at the working face(s).

B. The type and rate of product haulage including haulage system design

elements that influence the amount of spillage or dust produced.

C. The condition of hydraulic systems in terms of the potential of spray or other release of combustible fluids from the contained system.

This is an End Event in the Event Logic Tree as drawn.

6.6 Reduction of the Availability of a Fuel (i.e.. Control Fuel Exposure)

The reduction of the availability of a fuel is any act or arrangement that causes that fuel to be less exposed to influence by those energy environments

that can result in ignition. Most typically this involves either the

containment or covering of a fuel to barricade it from the fire inducing

environmental conditions. Typical examples include:

A. Use of safety cans or other suitable containers for flammable liquids.

13
B. Sprayed concrete or other coating of the ribs or coal roof in portions

of a mine.

This is an End Event in the Event Logic Tree as drawn.

CHAPTER 5 - CONTROL FUEL SUSCEPTIBILITY BRANCH (Figure 3)

4,2 Control Fuel Susceptibility

To be susceptible a fuel must be available. An available fuel is susceptible

to ignition if the inherent or situation induced conditions cause a fuel to be

in a state where the presence or an ignition source can cause the onset of

fire. Since ignition susceptibility applies only to those fuels that are available, all considerations of degree of success in this event are conditional on the degree of failure of Event 4.1, Control Fuel Availability.

Gate 4.2 - The degree of success in controlling fuel susceptibility is the sum

of the degree of success in maintaining environmental conditions outside the

combustible limits of the fuel plus the degree of success in controlling the

response to incident energy of those fuels in environments potentially within

the combustible limits of the fuel involved.

5,4 Maintain Environment Outside Combustible Limits of Fuel

A fuel is outside of the combustion limits of that fuel if the ratio of fuel

to oxidizer (air or oxygen) is such that combustion will not take place. For

gases, aerosols, or dusts this applies to the mixture of any of these in the

air. To solid materials such as piles of coal or gob this applies to the

interface between the solid material and the surrounding environment.

Gate 5.4 - The degree of success in maintaining environments outside the

combustion limits of the fuel is the sum of degree of success in maintaining

environments that are fuel rich plus the degree of success in maintaining

environments that are fuel lean.

14
6 . 7 Develop Fuel Rich Environment

A fuel rich environment is one in which either the concentration of fuel or

the shortage of air or other oxidizers is such that combustion cannot take

place

.

Typical applications of this approach include:

A. The exclusion or removal of oxygen by the use of an inert gas or other

inert material (rock dust, etc.) to encase or surround a condition (such

as welding) where high temperatures and fuels might necessarily be in

intimate proximity to each other.

B. The reduction of oxygen through absorption into the environment as occurs when gob or other abandoned areas are sealed.

C. The prevention of the mechanical dispersion of a combustible material

from vibration and from high pressure (spray) leaks from hydraulic

systems and as the secondary result of a methane ignition.

This is an End Event in the Event Logic Tree as drawn.

6.8 Develop Fuel Lean Environment

A fuel lean environment is one in which the amount of fuel is insufficient to

undergo the combustion process. The typical example of a fuel lean

environment exists in the properly designed mine exhaust stream that maintains

methane below its explosive limits.

This is an End Event in the Event Logic Tree as drawn.

5.5 Control Temperature Dependent Susceptibility

Temperature dependent susceptibility factors are those that control the level

of temperature at which a fuel (not maintained outside of combustible limits

15
by Event 5.4) volatilizes sufficiently to produce a combustible mixture

susceptible to ignition.

Gate 5.5 - The degree of success in controlling the temperature dependent

factors is a multi-variant relationship between the level of control of the

critical volatilization temperature of the fuel and the degree of control of

the temperature rise in the fuel.

6.9 Manage Critical Temperature of Fuel

The critical temperature of a fuel is that surface temperature at which the

rate of volatilization of combustible matter is such that the entry of an ignition energy can initiate fire as defined in Event 2.1, Prevention of Fire

Initiation. This is normally accomplished by techniques such as:

A. Use of noncombustible material (infinitely high critical temperatures).

B. Selection of materials that inherently have higher critical

temperatures

.

C. Treatment of material to increase the critical temperature of a material

.

This is an End Event in the Event Logic Tree as drawn.

6.10 Maintain Surface Temperature Below Critical Level

Given the degree of control of critical temperature, the susceptibility of a fuel is determined by the degree to which such fuel can be maintained below

that critical temperature. For each fuel there is potentially a different

critical surface temperature. Some fuels have critical temperatures below

ambient temperatures. For flammable liquids the critical temperature is

traditionally described in terms of flash point.

16
Gate 6.10 - The degree of success in maintaining surface temperatures below

the critical level is the degree to which there is concurrent success in

cooling any materials that have critical temperatures at or below ambient

temperature to a level lower than their critical temperature, and the degree

of success in preventing critical temperature rises in those materials that

have critical temperatures higher than ambient temperature.

7.1 Reduce Surface Temperature of Fuel Below Critical Temperature

Reduction of surface temperature below the critical temperature includes any

action or arrangement that either reduces the surface temperature directly as by surface cooling or which reduces the overall ambient environment below that

which is critical (e.g., ventilation cooling of a space to prevent selfheating)

This is an End Event in the Event Logic Tree as drawn.

7.2 Prevent Temperature Rise of Fuel

For those fuels where the critical temperature is above ambient,

susceptibility to ignition can be controlled by preventing rise in the surface

temperature of such material.

Gate 7.2 - The degree of success in preventing the surface temperature rise is

the sum of degree of success in preventing the impact of incident energy upon

the fuel, plus the degree of control of response of that fuel to incident

energy

.

8,1 Interpose Energy Transfer Barrier Between Energy Source and Fuel

Barriers may be total or partially effective in preventing the transfer of

heat energy, depending on their position and energy response. Such barriers,

may be on the heat source, on the target, or at some intervening point

between

.

17
This is an End Event in the Event Logic Tree as drawn.

8.2 Control Response to Incident Energy

The characteristic response to incident energy can be controlled or predicted

in terms of the characteristics of the incident energy source and the

responding characteristics of the fuel.

Gate 8.2 - The degree of success in controlling the response to incident

energy is a multi-variant relationship between the incident energy and the

resistance to incident energy impact of the individual item.

9,1 Incident Energy

Incident energy is that energy which reaches the fuel surface from all energy

producing sources.

This is an End Event in the Event Logic Tree as drawn, however, Functional

Branch A outlines the basic physical elements that determine the level of

incident energy.

Functional Branch A - Incident Energy (Figure 11)

The incident energy impact on a target fuel is the sum of the energy radiated

to that target plus the energy conducted to that target plus the energy

convected to that target.

A-l Radiation - Radiation is the transfer of heat from one body to another

by means of wave motion through space. The amount of energy radiated at

the target is a function of the absolute temperature of the radiator (A4), the emissivity (i.e., radiant efficiency) (A- 5), and the

configuration or viewing factor relationship between the fire source and

the target (A-6)

.

The amount of radiation varies with the fourth power

of the absolute temperature and directly with emissivity and

configuration factor. The emissivity or radiation efficiency of many

18
solid materials varies with the temperature of that material.

Configuration factor is a spherical geometry relationship that depends

upon the size of the radiation source (length and width) , the distance

between the radiation source and the target, and the angle between the

face of the radiator and the line site to the target.

A- 2 Conducted Energy - Conduction is the transfer of heat from one part of a body to another part of the same body or from one body to another in

physical contact with it.

A. Conduction through a body (A- 7) is a function of the

temperature differential between the exposed and the

unexposed faces of the heat conducting body (A- 8) , the

thickness of the conducting body (A-9) , the thermal inertia

(KpC) of the conducting body (A- 10) and the thermal

conductivity (K) of the conducting body (A-ll)

.

B. Conduction between physically contacting bodies (A- 12)

is a function of the temperature differential between

the bodies (A-13) and the effective heat transfer

coefficient involved (A-14).

A- 3 Convected Energy - Convection is the transfer of heat from one point to

another within a fluid (gas or liquid) by movement of heated portions of

the fluid or by the mixing of one portion of the fluid with another.

The convected energy is a function of the temperature differential and mass of the heated portion of the fluid (A-15) , the relative position of

the source of the heated gas and the target (A- 16) , and the cooling of

the gases in transit (A-17) . The cooling of the gases in transit are in

turn a function of any energy lost from the gases through radiation

(A- 18) through conduction to other portions of the fluid mass through

dilution and mixing (A- 19) and the conduction of energy due to contact

between the fluid and any other body (surface) (A-20)

.

19
9.2 Resistance to Energy Impact

The resistance to energy impact is the characteristic response of a material

to the impact of incident energy on it. This response is in terms of the

speed at which surface conditions progress toward equilibrium with the

incident energy. The slower the surface temperature rise the more resistance

to energy impact.

This is an End Event in the Event Logic Tree, however, Functional Branch B

outlines the basic physical elements that control the response of a material

to incident energy.

Functional Branch B - Resistance to Energy Impact (Figure 11)

The resistance to energy impact is a combined function of the thickness of the

material (B-l), the reflectivity of its surface (B-2), and its thermal inertia

(B-3)

.

Thermal inertia is a measurement of the capability of the target

material to receive heat energy and absorb or distribute it within. Thermal

inertia is a function of the thermal conductivity (B-4)

,

the density (B-5),

and the specific heat (B-6) of the material. Some of these factors vary

through the course of exposure with temperature change. The target surfaces

of low thermal inertia materials quickly come to equilibrium with incident

energy (heat up quickly) . Conversely, the target surfaces of high thermal

inertia materials tend to resist coming to equilibrium by dissipating the

energy through the mass of the material. As materials become thicker,

relative importance of thickness decreases. For very thin materials (cloth,

thin plywood, coal dust, etc.) thickness is a critical element. For thicker

materials such as heavy timbers or the undisturbed coal mass, the thickness is

infinite as far as thermal energy transfer is concerned.

20
CHAPTER 6 - LIMIT IGNITERS BRANCH (Figure 4)

3.2 Limit Igniters

An igniter is any energy source sufficient to raise the temperature of an ignitable fuel (see Event 3.1) to the transition from a non-burning state to

fire initiation in accordance with the definition of fire initiation used in

the particular application of the tree.

Gate 3.2 - The degree of success in limiting igniters is the degree to which

there is concurrent control of both pilot ignition sources and self (auto)

ignition potentials. The contribution of the degree of success in limiting

igniter to the overall Event Logic Tree success is conditional on the degree

of failure of Event 3.1 (i.e., limiting the availability of ignition

susceptible fuels). By definition, the simultaneous failure of both Event 3.1

and 3.2 (i.e., the joining of a susceptible, ignitable fuel and an igniter) is

failure of Event 2.1, Prevention of Fire Initiation.

4.3 Control "Pilot" Ignition Potential

Ignition pilots are energy sources external to the potential fuel that can

start the combustion reaction necessary for fire initiation as specified by

Event 2.1, Prevention of Fire Initiation, when exposed to a fuel in an ignitable condition as defined by Event 3.1.

Gate 4.3 - The degree of success controlling pilot ignition potential is the sum of the degree to which pilot ignition sources are excluded from areas of

fuel ignitability plus the degree to which those sources that are not excluded

are otherwise controlled to prevent the imposition of ignition level energy on

the ignitable fuels.

5,6 Prohibit. Limit. Exclude

The objective of this event is to prevent the intersection of a pilot ignition

source with an ignitable fuel. The extensive degree of ignitable fuel and the

21
frequency and variety of pilot ignition sources inherent in coal mines tends

to limit the extent of success of this event. However, the degree that pilot

ignition sources such as open flames, arcing equipment, and hot bodies can be

kept out of the mine, add to the success of this event. Success is also

achieved in cases where the location of pilot ignition source, such as welding

equipment, is controlled to separate it from ignitable fuels.

This is an End Event in the Event Logic Tree as drawn.

5.7 Other Protection

Other protection includes any devices or arrangements that preclude a potential pilot ignition source from causing ignition including: reduction of

the level of energy of a device below that necessary to cause ignition of the

susceptible fuel; inherently safe electrical equipment; equipment so designed

that if a combustible mixture reaches the point where the energy level is

sufficient for ignition potential, propagation will take place (e.g.,

explosion proof equipment and the flame arrestors in methane detection lamps)

;

or other pilot igniter protection arrangements.

This is an End Event in the Event Logic Tree as drawn.

4,4 Control Self (auto) Ignition Potential

Auto ignition is defined as ignition that occurs in the absence of pilot

igniters. In this case ignition results from raising the temperature of the

fuel itself to the point where its own surface temperature exceeds the energy

level necessary to ignite it or the material volatilized from it.

Gate 4.4 - The degree of success in controlling auto ignition as a contribution to the overall degree of success in limiting igniters is that

degree to which auto ignition is prevented when there are no pilot igniters

(i.e., when Event 4.3 is also successful). Within this constraint, the degree

of success is the degree of success in concurrently preventing both internally

induced (self) heating and externally induced heating.

22
5.8 Internally Induced Heating Control

Internally induced heating is defined as that heating in which the temperature

of the heated material is higher than the surrounding ambient atmosphere.

Such heating is normally a function of the inherent self heating

characteristics of the material (e.g., coal and its entrained volatile

products); the total mass, the amount of radiant surface to dissipate heat (in

terms of a surface to mass ratio), the temperature of the mass, and the

temperature of the surrounding environment.

This is an End Event in the Event Logic Tree as drawn.

5,9 Externally Induced Heating Control

Externally induced heating is defined as heating of a mass from an external

environment or a heat source in the external environment at a higher

temperature than target fuel. The factors controlling this event are identical to those controlling the development of Event 5.5, except that the

critical temperature of concern is critical ignition temperature rather than

critical volatilization temperature.

This is an End Event in the Event Logic Tree as drawn.

CHAPTER 7 - LIMIT INHERENT POTENTIAL BRANCH (Figure 5)

This branch of the tree relates to the inherent or unencumbered energy

production potential of an ignited fuel. It does not treat those actions or arrangements such as suppression or confinement that can mitigate this

potential, nor does it treat the resulting threat that can occur from smoke

gases and other mass products produced, or separate threats such as oxygen

depletion or mine collapse. Each of these are covered in separate chapters.

23
15.1

Limit Inherent Potential

The inherent potential of a fire is defined as the extent of spread of the

combustion process and the resultant energy release if there are no successful

installed or emergency instituted devices or efforts to halt, limit, or terminate it.

Gate 15.1 - The degree of success in limiting the energy potential is the

degree of success in concurrent control of the extent of the burning area, the

energy characteristics of the burning area, and the duration of burning.

16 . 1 Control Extent of Burning Area

The extent of burning area is defined as the surface area of all materials

undergoing destructive oxidation at any time plus all portions of the flame

body that are undergoing energy generating combustion reactions.

Gate 16.1 - The degree of success in controlling the extent of the burning

area is the degree to which there is concurrent control of both the extent of

flame spread across combustible surfaces and the control of the involvement of

additional fuels through other means.

17.1 Control Surface Flame Spread

Surface flame spread is defined as the progressive involvement across the

surface of a continuous or nearly continuous combustible face from a fire source emitting from or in intimate contact with the surface.

Gate 17.1 - The degree of success in controlling the surface flame spread is

the Siam of the degree of success that the response of the materials involved can be controlled to obstruct or retard flame spread plus the degree to which

the external environmental factors can be controlled to prevent energy

reinforcement of flame spread.

24
18,1

Control Material

Control of a material relates to both the inherent flame spread

characteristics of the material and the response of that material to incident

energy from its own flame or from other sources.

Gate 18.1 - The degree of success in controlling surface flame spread through

control of materials is the sum of the degree that the chemical burning

characteristics of the material are controlled and the degree to which the

thermal response of a material is controlled.

19.1 Control Chemical Response

Chemical response is the subjectivity to pyrolysis of the constituent

molecules volatilized from the base material or reacted in place in the

material matrix. Methods of controlling this process include the use of

materials that are either non-combustible or inherently have low

combustibility (e.g., use of masonry block or transite material to construct

shop partitions or the clearing of the overhead to bare rock to eliminate the

combustibility of the ceiling) . Alternatively chemical control of the

response of an inherently combustible material can be enhanced by fire

retardant treatment (e.g., fire retardant treated wood or fire retardant

treated brattice)

.

This is an End Event in the Event Logic Tree as drawn.

19.2 Control Temperature Rise of Unignited Portions of Surface

The unignited portions of the surface must be raised to a temperature

sufficient to evolve an ignitable concentration of volatilized combustion

products from the uninvolved surface in front of the flame front. The energy

to do this may come from the advancing fire on the adjacent surfaces or from

any other source.

25
Gate 19.2 - The degree of success in controlling the temperature rise of

unignited portions of a surface is the sum of the degree of success in

interposing barriers to energy transfer between the energy source and the

unignited portion of the surface plus the degree of success in controlling the

response of the surface to the incident energy that strikes it.

20.1 Obstruct Energy Transfer to Surface

The energy transfer to the surface of a combustible material is limited to

that energy that actually reaches and is transferred to that material.

Gate 20.1 - The degree of success in obstructing energy transfer is a multivariant functional relationship between the energy exposure and the

effectiveness of the obstruction to the transfer of such exposure to the

unignited surfaces.

21.1 Energy Exposure

Energy exposure includes all forms of energy that are present in a form and

level that has a potential of impacting on a target material.

This is an End Event in the Event Logic Tree as drawn, however, Functional

Branch A, as described in Chapter 5, covers the factors that control the level

of energy exposure and the potential incident energy where no obstructions are present

.

21.2 Effectiveness of Obstructions to Energy Exposure

Obstructions to energy exposure include any type of barrier or energy

absorbing media between the energy producing source and the target surface;

insulation or barriers applied to the target; and cooling systems (e.g., water

sprays) that remove energy reaching the target before it can be transferred to

the target surface.

This is the End Event in the Event Logic Tree as drawn.

26
20.2

Control Response to Incident Energy

The response of the material to incident energy (relative to surface flame

spread) is the potential of the surface zone of that material to rise in

temperature given the degree of energy impact of the surface (i.e., degree of

failure of Event 20.1).

Gate 20.2 - The control of response to incident energy is a multi -linear

function of the relationship between the incident energy actually impacting on

the target surface and the resistance of that surface to such energy impact.

21.3 Incident Energy

The incident energy striking the surface zone is all of the energy not

obstructed in accordance with Gate 20.1.

This is an End Event in the Event Logic Tree as drawn.

21.4 Resistance to Energy Impact

The resistance to energy impact is the capability of the target surface to

receive incident energy and distribute it within or through the target

material in such a manner as to retard the tendency of that material to rise

in surface temperature towards equilibrium with the incident energy.

This is an End Event in the Event Logic Tree as drawn, however, the functional

elements controlling the resistance to energy impact are those described in

Functional Branch B previously discussed under Chapter 5.

18,2 Control Level of Energy Exposure to Unignited Portions of Surface

Event 18.1 governs the response of a surface to an exposing energy environment

relative to fire initiation. This event is designed to govern the response of

27
a surface to an exposing energy environment that occurs after fire initiation.

In all other aspects, the two events are identical.

Gate 18.2 - The degree of success in controlling the energy exposure is the

degree that there is concurrent control of the total energy developed by the

exposure produced by the involved portions of the surface along with control

of any other exposure produced from other aspects of the general environment.

19.3 Control Exposure from Involved Portions

The transfer of energy from the involved (burning) portions is primarily from

the flame and radiative in nature. In some cases, conductive energy may be a factor. This is most likely in the slow propagation characteristic of

smoldering fires.

This is an End Event in the Event Logic Tree as drawn.

19.4 Control Exposure from General Environment

In addition to the energy directly from the flame, the rate of propagation of

fire across a combustible surface is also strongly influenced by any

supportive incident radiation coming from any other source. This is important

when energy levels in the environment reach levels that impose incident energy

on portions of the surface at levels higher than the energy transfer from its own burning flame (Event 19 . 3 ). The factors controlling this event are the same as those involved in Event 16 . 2 , Control Fire Intensity.

This is an End Event in the Event Logic Tree as drawn.

17.2 Control Other Means of Extension of Burning Area

In addition to the degree of fire extension resulting from the degree of

failure to control surface flame spread, other forms of fire extension can occur involving materials that are either separated from the continuous

28
burning surface, or if part of such surface, are sufficiently removed from the

involved area that they are not part of the flame spread phenomena.

Gate 17.2 - The degree of success in preventing other means of extending the

burning area is the degree of success in concurrently preventing fire induced

ignition of other fuels along with controlling environment induced involvement

(flashover and other ventilation control conditions).

18.3 Prevent Fire Induced Ignition of Other Fuels

Fire induced ignition of materials is classified as successive ignitions

following the same functional controls as the prevention of fire initiation.

For this reason, the guidance in the tree refers the user to Event 2.1. The

conditions covered in 2.1 are then repeated at the higher level of energy in

the exposing fuel.

This is an End Event in the Event Logic Tree as drawn.

18.4 Control Exposure from General Environment

The energy exposure resulting from the increase in environmental energy

conditions can induce flashover or other means of propagation without the

direct transfer of energy from the flame or flame plumes of the burning

material. The factors controlling this event are the same as those involved

in Event 16.2, Control Fire Intensity.

This is an End Event in the Event Logic Tree as drawn.

16.2 Control Fire Intensity

The fire intensity is defined as the position and level of the fire induced

energy emitting bodies (solid, liquid, or gas) in the environment. Normally

this is defined in terms of temperature distribution and appropriate

efficiency factors such as emissivity, specific heat, or other factors

relative to heat transfer.

29
This is an End Event in the Event Logic Tree as drawn, however, Functional

Branch C outlines the elements that are the parametric variables controlling

the energy characteristics of a given environment.

Functional Branch C - Fire Intensity (Figure 12)

The overall energy characteristics of an environment are the combined function

of the rate of energy production, both at any instant, and the history of that

production through the course of the fire (C-l) ; the energy losses, both at

any instant, and the history of energy losses through the course of the fire

(C-2); and the physical arrangement of the environment (C-3).

The energy production rate is in turn a function of the incident energy (C-4)

,

the response of materials to incident energy ( C - 5

)

(as outlined in Functional

Branch B) , the volatilization rate of the materials as a function of the

surface temperature (C-6), and the energy produced per unit mass volatilized

(C-7).

The energy produced per unit mass volatilized is a function of the inherent

chemical makeup and properties of the materials involved (C-8), and the

availability of the air necessary for the combustion process (C-9).

The air for combustion is controlled by the mass available (a function of the

physical environment) (C-10), the entrainment of the air into the fire plume

(C-ll), and the oxygen content of the air (C-12).

Energy losses include those that are vented (i.e., convected from the fire

scene) (C-13), those that are radiated from the fire plume (C-14), and those

that are transferred to the environment by conduction (C-15).

The influencing physical arrangement of the environment includes all factors

of geometry such as height, volume, plan dimensions, and slope. In addition,

important environmental considerations relate to the ventilation means by

30
which the fire can obtain the necessary air, and any means available to vent

combustion products.

16.3 Control Fire Severity

Fire severity is defined as the total high temperature energy imposed by the

fire through its duration or up to point of interest. It is frequently

measured in terms of a cumulative time versus temperature curve or occasionally as rate of energy transfer versus time.

Gate 16.3 - The degree of success in controlling severity is the sum of the

degree of success in controlling fire intensity and the degree of success in

limiting the duration of such intensity through limitation of the total

available fuel mass for combustion.

17.3 Control Fire Intensity

Event 17.3 is identical to Event 16.2.

This is an End Event in the Event Logic Tree as drawn.

17.4 Limit Available Fuel Mass

The available fuel mass is defined as all materials that are both capable of

releasing energy under fire exposure and subjected to oxidation reaction,

given the degree of failure to control fire intensity. This is normally

measurement of the mass of such material.

This is an End Event in the Event Logic Tree as drawn.

31
CHAPTER 8 - CONTROL BY INTERVENTION BRANCH (Figure 6)

15.2 Control by Intervention

Intervention is the application of any fixed or time-of-fire feature or act

that causes a termination, slowing, or other reduction in the otherwise

potential fire energy threat. Intervention impacts on the outcome only to the

degree that it reduces a threat that is not limited or controlled by the

features under the Limit Inherent Potential Branch (Chapter 7).

Gate 15.2 - The degree of success of control by intervention is the sum of the

degree of success of control by suppression or other forms of termination plus

the degree of success of control by confinement.

16.4 Control by Suppression of Burning

Suppression is any action that stops or reduces the extent, intensity, or severity of fire below the inherent potential residual from the degree of

failure of Event 15.1.

Gate 16.4 - The degree of success in control by suppression is the sum of the

degrees of success of the collective impact of control by removal of fuel

availability, cooling or quenching, oxygen deprivation, or other means.

17.5 Control by Removal of Fuel Availability

The removal of fuel availability is any action that extracts fuel from any area where it can become involved as a result of the conditions outlined under

Event 15.1. Typical actions include the physical removal of an exposed fuel

from the threat of an advancing fire (removal of coal in a pile or bunker) or

the covering of a threatened fuel with a barrier to make it inaccessible.

This is an End Event in the Event Logic Tree as drawn.

32
17.7 Control by Cooling

Cooling is any action that removes heat from the fire bed or the produced hot

gases or heated surface. It also includes forms of cooling that increase the

difficulty of ignition of unignited materials (primarily by wetting) . For the

most part, the cooling media is water that may be manually or automatically

applied in a traditional form of water or as high expansion foam. A common

set of functional criteria apply to all such systems. These criteria are outlined in Functional Branch D.

This is an End Event in the Event Logic Tree as drawn, however, Functional

Branch D provides interrelationships of the parameters that control the degree

of success of a suppression system.

Functional Branch D - Suppression System (Figure 13)

The capability of a suppression system (manual or automatic) is a function of

its availability relative to the area of suppression needs (D-l), its ability

to recognize and respond to the need (D-2) , and its suppression capability

when applied (D-3).

Availability is defined as the proximity of the sensing and activation devices

to the fire of a fixed system and the proximity and availability of a safe access path for persons and equipment in cases of manually operated systems.

Response is a combined function of the sensitivity of the responding mechanism

(D-4) and its initiation reliability (D-13). Initiation reliability (D-13) in

the case of automatic equipment is reliability, in terms of sensing the fires

signature and of activating all elements necessary to deliver the suppression

agent

.

Sensitivity (D-4) is the response ability of the initiating device (or

persons) to the fire situation created by the level of fire characteristics

resulting from the degree of failure of Event 15.1.

33
Sensitivity is a multi-variant function of the signature production and

transmission (D-5) and the detector response to it (D-9) . In such case, the

signature production of interest is that to which the detector can respond.

Signature production and transmission (D-5) is in turn a function of the

actual energy signature production of the fire (D-6), the relative position ofthis production to the detector location and the level of energy in the

detectable signature media (D-7), and the space geometry involved (D-8)

.

Detector response (D-9) is a function of the resistance of the detector to

signature admission or accumulation in the actual detection zone (D-10), the

signature level required to activate the detector (D-ll), and any internal

system time constants or delays (D-12). In the case of fixed systems, these

internal time constraints are normally mechanical or electronic. In the case

of human detectors, they may be administrative.

Suppression (D-3) is the concurrent capability of the suppression system once

it has responded (D-14), and the trans-fire reliability in terms of the

ability of the system to stay in proper operating order under the ensuing fire

exposure for a sufficient period of time to fulfill its function (D-17).

Suppression capability is a mass density function relationship between the

extent of burning area and intensity of the fire (degree of failure of Event

16.1 and 16.2) (D-15) relative to the agent's capability as applied against

the given levels and extent of burning (D-16).

17.6 Control by Oxygen Deprivation

Oxygen deprivation is any activity which prevents oxygen from reaching the

fire

.

Gate 17.6 - The degree of success in control of fire through oxygen

deprivation is the sum of the degree of control obtained by replacing oxygen

with inert gas or by exclusion of oxygen by other means.

34
18,5 Replace Oxygen with Inert Gas

Inert gases include both inert gases especially designed or generated for the

purpose of fire control such as carbon dioxide or nitrogen and the inert

products of combustion produced by a fire itself.

This is an End Event in the Event Logic Tree as designed, however, the

parameters described in Functional Branch D also apply to inert gas systems.

18,6 Exclude Oxygen by Other Means

Other means include any non- gas approach. Such are likely to involve covering

the burning material with a solid material such as rock dust or blocking

oxygen entry by sealing or other means to prevent the fire from drawing fresh

air

.

This is an End Event in the Event Logic Tree, however, the performance of

systems for exclusion of oxygen are also subject to the parametric element

described in Functional Branch D.

17.8 Control by Other Means

All other means of suppressing fire are covered under this category. The

principal envisioned mechanisms are those approaches that interfere with the

chemical train of the combustion process such as fire extinguishment using

halogenated agents

.

This is an End Event in the Event Logic Tree, however, as with all other

suppression systems the functional parameters in Functional Branch D apply.

16.5 Control by Confinement of Extent of Burning

Confinement of the extent of burning is defined as the establishment of a barrier or other perimeter that prevents the advance of the combustion process

beyond some point.

35
Gate 16.5 - The degree of success of control by confinement is the degree of

the concurrent success in maintaining the completeness of the perimeter, its

structural endurance, and its thermal endurance.

17.9 Perimeter Completeness

Completeness is the degree to which the perimeter (normally defined by

stopping or another barrier) is sufficiently continuous to prevent the passage

of fire and flame or other hot gases sufficient to cause ignition on the

unexposed side of the barrier. The degree of success in completeness is a measurement of the degree of prevention of ignition passage rather than a measurement of degree of totality of the perimeter.

Perimeter completeness is an End Event in the Event Logic Tree as drawn,

however, Functional Branch E lays out the factors that determine the

probability of success in terms of completeness.

Functional Branch E - Barrier Completeness (Figure 13)

The functional factors that determine the probability that ignition will pass

through any openings in a barrier include the number, size and position of the

openings (E-l), the exposing energy level and position as developed from the

degree of failure in Events 16.1 and 16.2 (E-2), the location of the flame

relative to barrier openings and the amount of excess pyrolysate in the flame

body (E-3), and the relative position of external (exposed) fuel on the

unexposed side of the barrier vis a vis the barrier openings (E-4)

.

Failure

is considered to be the transfer of ignition to a fuel on the unexposed side

of the barrier.

17.10 Provide Structural Endurance

Structural endurance is the capability of a perimeter to hold its shape and

position during the exposure presented by the imposed fire conditions. Where

a barrier or other perimeter member depends upon other members (columns,

36
beams, etc.), the endurance of those members is an integral part of structural

endurance

.

Gate 17.10 - The degree of success in providing control through structural

endurance is a multi -variant relationship between the fire's severity (the

degree of failure of Event 16.3), and the structural endurance of the member.

18.7 Fire Severity

Fire severity is the degree of failure to control the severity as defined

under Event 16.3.

This is an End Event in the Event Logic Tree as drawn.

18.8 Structural Endurance Capability

Structural endurance is the capability of a perimeter element and its

supporting members as installed and protected at the time of fire to withstand

and hold their shape, form, and load when subjected to fire.

This is an End Event in the Event Logic Tree, however, Functional Branch F

points out the two essential considerations in functional parameters.

Functional Branch F - Endurance (Figure 13)

Endurance of a member exposed to fire is a combined function of the inherent

endurance of that member (F-l) plus any endurance enhancement applied at the

time of exposure (F-2) . Endurance enhancement is most likely in the form of

water spray or other means intended to reduce the impact of energy incident on

the member.

17,11 Provide Thermal Endurance

Thermal endurance is the capability of a perimeter element to resist the

conductive transfer of energy from the exposed to the unexposed side. The

37
measurement of the degree of success is the degree to which ignition through

energy transfer is avoided.

Gate 17.11 - The degree of success in providing control through thermal

endurance is a multi -variant relationship between fire severity and the

thermal endurance response of the element.

18.9 Fire Severity

Fire severity is identical to the fire severity described under Event 18.7.

This is an End Event in the Event Logic Tree as drawn.

18.10 Thermal Endurance Capability

Thermal endurance capability is the ability of the perimeter system as installed to prevent the transfer of energy from the exposed to the unexposed

side

.

This is an End Event in the Event Logic Tree as drawn, however, Functional

Branch F provides factors related to the development of endurance.

CHAPTER 9 - MASS PRODUCT THREAT BRANCH (Figure 7)

14,2 Control Mass Products Threat

Mass products are defined as the various chemical species and particulate

products generated by the combustion process or by efforts to extinguish or control that process. Mass products also include any air or other gases

entrained into the flow of fire generated products. Mass products include,

but are not limited to, all of those fire products usually referred to as smoke and toxic gas

.

38
Gate 14.2 - The degree of success in controlling mass product threat is the sum of the degree of success in controlling the production of such products

plus the degree that the movement of those products produced is managed.

15.3 Control Product Production

Product, as used herein, is the conglomerate airborne material produced as byproducts of fire, airborne elements of extinguishing agents, and any

products produced as a result of the application of such extinguishing agents

in the fire environment.

Gate 15.3 - The degree of success in controlling product production is a multi-variant relationship between the fire energy threat (i.e., lack of

control of such threat under Event 14.1) and the products produced given such

threat

.

16.6 Fire Energy Threat

Fire energy threat is the degree of failure of Event 14.1, that is, the extent

and magnitude of fire threat that will potentially be available. The

dimensions of measurement are in terms of rate of energy release with such

additional factors as are pertinent to production of product gases. These

factors include variables such as extent of flaming and sufficiency of oxygen.

This is an End Event in the Event Logic Tree as drawn.

16.7 Products Produced

The products defined by this event are those produced when the material is

exposed to the fire energy threat defined in 16.6, including the impact of any

intervention approach covered under Event 15.2.

This is an End Event in the Event Logic Tree as drawn.

39
15.4 Manage Product Movement

Product movement is the mass transfer of all or part of the products produced.

Gate 15.4 - The degree of success in managing product movement is the sum of

the degree of success in controlling the movement energy that provides the

dynamic head to the gas mass plus the degree to which this movement is

controlled given the dynamic head.

16.8 Control Movement Energy

Movement energy is the pressure differential above the normal for the area. This pressure differential is the measurement of the energy forces capable of

moving the gas body.

Gate 16.8 - The degree of success in controlling movement energy is the degree

to which there is concurrent control of the fire induced energy and energy

induced into the gas by other means.

17,12 Control Fire Induced Energy (Buoyancy')

Fire induced energy is that energy caused by the thermal expansion of the gas

body due to the fire induced energy which remains in the gas body.

Gate 17.12 - The degree of success in control of fire induced buoyancy is the sum of the degree of success in reducing the gas body temperature by adding a cooling means to the gas mass plus the degree of success in cooling the gas

body temperature by transfer of energy to other materials.

18.11 Control by Adding Cooling Agents

Cooling agents are any liquid or gas added to the gas mass that results in a lower temperature of the resulting mass. Most commonly this is either from

dilution with cooler air or from a water spray, automatically or manually

applied.

40
This is an End Event in the Event Logic Tree as drawn.

18.12 Control by Transfer to Other Masses

Heat transfer to other masses is defined as that heat conducted to masses such

as the roof faces and ribs of the mine as a result of the contact of the hot

gases with those bodies or similar transfer by radiation. Each of these

transfers is a function of the temperature differential between the gas body

and the energy receiving surface. In the case of radiant transfer, it is also

a function of the emissivity (energy transmission efficiency) of the gas.

This is an End Event in the Event Logic Tree as drawn.

17.13 Control Other Gas Movement Forces

Other energies include any mechanism other than the entrained heat that causes

a pressure differential resulting in gas movement. (Examples of sources of

such energy would include fans, barometric pressure differentials, and wind.)

Gate 17.13 - The degree of success in controlling other gas movement energy is

the degree of success in the concurrent control of each such potential energy.

18,13

Control Mechanically Induced Forces

Mechanically induced forces are those forces developed by a mechanical

arrangement designed to move air or provide gas pressure differentials capable

of moving the gas mass. Generally this is dominated by the mine ventilation

system but also includes any casually produced forces such as might be induced

by any piston action of a hoist or other mechanism.

This is an End Event in the Event Logic Tree as drawn.

41
18.14 Control Barometric Induced Forces (Stack Effect)

Barometrically induced forces or stack effect are those that result from the

pressure differential caused by the difference in barometric pressure between

two points in the mine system and is normally a function of the height of the

shaft and the total barometric pressure resting at the base of the shaft versus the total barometric pressure in some other connected part of the

system.

This is an End Event in the Event Logic Tree as drawn.

18,15 Control Wind Induced and Other Forces

Wind induced forces are those caused by natural winds that may either blow

into the mine or across the face of an opening. "Other forces" is a catch-all

statement to cover any other gas movement energy forces. No examples of such

other forces are included.

This is an End Event in the Event Logic Tree as drawn.

16,9 Control Movement

The movement of a gas body is the transfer of a mass from one location to

another. This event is conditional on the movement energy residual due to the

degree of failure involved in Event 16.8.

Gate 16.9 - The degree of success in control of movement is the sum of degree

of success in obstructing movement with barriers plus the sum of degree of success in managing the fluid dynamics of that not controlled by barriers.

17.14 Obstruct Movement with Barriers

Barriers include any obstacle to the flow of a gas body. In general, a barrier is not effective unless it encloses all or most of the potential gas

movement opening. Most barriers have some degree of potential gas leakage,

42
depending on the pressure differential between the clean and smoke laden side

of the barrier. The success of barriers is also dependent upon their success

as a confinement media as covered in Event 16.5.

This is an End Event in the Event Logic Tree as drawn.

17.15 Manage Fluid Dynamics

The fluid dynamics of concern are the flow, movement, and concentration of

species in the gas body. This is considered conditional on the degree of

failure to obstruct the movement with barriers.

Gate 17.15 - The degree of success in managing fluid dynamics is the sum of

the degree of success in controlling the gas mass concentration, by dilution;

controlling the gas mass flow by exhaust or venting; and control of gas

movement with pressure differentials.

18.16 Control by Dilution

Control of the gas mass by dilution consists of entering air into the gas mass

to reduce the density of harmful products. Dilution in this event is the same dilution as covered under Event 18.11, but the function is different and the

resulting degree of success for a unit mass of dilution will not be the same

in these two events.

This is an End Event in the Event Logic Tree as drawn.

18.17 Control by Exhaust or Venting

Exhausting or venting in this context is any mechanism that removes the

products from the mine using either the buoyant force of the hot gases itself

or a fan induced arrangement which draws the undesirable gases to the venting

fan

.

This is an End Event in the Event Logic Tree as drawn.

43
18.18 Control with Pressure Differential

Control by pressure differential covers any approach where a force is created

by fans or any other means that develop a head pressure on the clean area higher than the pressure imposed by the gas mass, thereby blocking its advance

or forcing its retreat. Frequently pressure differential approaches are used

in combination with barriers to control the degree of failure to obstruct gas

flow inherent in the barrier. In coal mines, it is also possible to create

pressure differentials in selected entry ways without special barriers at the

interface

.

This is an End Event in the Event Logic Tree as drawn.

CHAPTER 10 - OTHER FIRE INDUCED THREATS BRANCH (Figure 8)

14,3 Control Other Fire Induced Threats

"Other Fire Induced Threats" is an open ended definition covering both the

identified and potentially yet unidentified threats not covered under the

definition of fire energy threats or mass products threats. This includes,

but is not limited to, the threats resulting from fire induced depletion of

oxygen, roof or structural collapse, and shock waves as might be induced by a fire induced explosion.

Gate 14.3 - The degree of success in controlling other fire induced threats is

the degree of concurrent control of fire induced depletion of oxygen,

prevention of roof or structural collapse, control of shock waves, and control

of other threats.

15,5 Control Oxygen Depletion

Oxygen depletion is the lowering of the oxygen fraction in a portion of the

mine below that necessary for life support. Fires, fire induced conditions,

44
and efforts to attack fire may all result in depletion of the oxygen in the

environment. It may occur in the fire product gas stream or in other areas.

This is an End Event in the Event Logic Tree as drawn.

15.6 Prevent Mine Collapse

Mine collapse is defined as the failure of any part of the mine roof or of any

other element in a manner that poses a threat.

This is an End Event in the Event Logic Tree as drawn.

Prevent Hazardous Shock Waves or Other Threats

Ignition of combustible gases such as methane or carbon monoxide, or other

environmental situations, can initiate a shock wave or pressure surge through

the mine shaft posing threat to persons and property.

Other threats are expected to occur but have not been defined at this stage of

development of the Event Logic Tree. The inclusion of "Other" in this gate is

to maintain an open ended system permitting future analysis of any

unidentified threats.

This is an End Event in the Event Logic Tree as drawn.

CHAPTER 11 - LIMIT OF EXCLUDE "EXPOSED" BRANCH (Figure 9)

24,1 Limit or Exclude "Exposed"

The term "exposed" is defined as those persons, property, or operational

capability whose harm would be detrimental to the achievement of the fire

safety objectives stated in Event 1.0. Exclusion is defined as prohibiting

entry of the "exposed" into the mine. Limit is defined as allowing entry but

restricting the total amount, or concentration of importance with the mine.

45
Gate 24.1 - The degree of success in achieving protection of the "exposed" by

limiting or excluding the "exposed" is the degree that persons, property, or capability that might otherwise be in the mines and subject to harm are kept

out of it.

The prominent approaches are identified as individual events in the Event

Logic Tree. Each is mutually exclusive from the other.

25.1 Limit Access to the Mine

Limiting access to the mine can be by a prohibition on entry of persons,

property, or operations into the mine. It can include the relocation of an essential process outside the mine as a surface operation, etc.

26.1 (Limit Access to Mine) at All Times

26.2 (Limit Access to Mine) at All Times of Specific Conditions. Threats

or Potentials

Examples would include clearing of the mine upon the discovery of a hazardous

condition such as unacceptable methane concentration or the undertaking of some specifically dangerous operation such as under certain blasting

conditions

.

25.2 Limit Access or Concentration of "Exposed" in Specific Areas of Mine

The prime example is the prohibition of entering under unsupported roofs.

Other examples might include prohibition of or limitation of access to

abandoned areas, limitation of the number of persons in specific work teams,

etc

.

26.3 Limit Access or Concentration to Specific Areas (at all times)

26.4 Limit Access or Concentration in Specific Areas at Times of Specific

Conditions. Threats, or Potentials

46
25.3 Evacuate in Case of Potential Thre a

t

The removal or evacuation of persons at the time of threat such as discovery

of fire. It may consist of removal of all persons or removal of those persons

who are either specifically endangered or do not contribute to the control of

the threat.

CHAPTER 12 - SAFEGUARDING "EXPOSED" BRANCH (Figure 10)

24.2 Safeguard "Exposed" from Given Threat

"Exposed" is any person, property, or production capability whose harm will

reduce the degree of accomplishment of the objectives in Event 1.0. The

specific "Exposed" covered in this event represents all the potential

"exposed" that is not excluded or limited by Event 24.1. The threat is that

which is residual from the result of the degree of failure of Event 13.1,

Control Threat.

Each of the events in this branch are functionally dependent on all or the

applicable portion of Functional Branch G.

Gate 24.2 - The degree of success in safeguarding the "exposed" from a given

threat is the sum of the degree of success in protecting the "exposed" in

their work place plus the degree of success of relocating the "exposed" to inmine refuge areas plus the degree of success in evacuating the "exposed" from

the mine

.

Functional Branch G. Factors Controlling Protection of "Exposed" (Figure 14)

The functional factors related to protection of "exposed" involve a multivariant relationship between the total threat (described in terms of extent,

intensity, and severity resulting from the degree of success in 13.1 (G-l)),

and the avoidance of harm by the "exposed" given that threat (G-2).

47
The ability to avoid harm is in turn a multivariant function of the tolerance

of the "exposed" (in the case of humans, their ability to survive and/or

function, in the case of physical property the ability to withstand damage

under the given degree of exposure) (G-3) , and the positions of the "exposed"

relative to the position of the threat (G-10). The position of "exposed" in

turn is a function of his ability to move (G-4) and movement actions that use

that ability (G-ll).

The ability to move (G-4) is a function of the physical capability of the

"exposed" to move (or be moved if the "exposed" is inanimate) (G-5), and the

fire safety characteristics of the movement route (G-6). The fire safety

characteristics of the movement route (G-6) can be described as functions of

the safety of the access from the position of the "exposed" to the route

(G-7), the capacity or capability of the route to handle the "exposed" (G-8),

and the security of the route (or place of protection if such a place is

involved) against the intrusion of fire products (G-9).

The security of the route or place can be determined through events that are

the same as the events described in Gate 16.5, Control by Confinement if the

objective of that gate is revised from "Extent of Burning" to "Extent of

Intolerable Conditions".

The movement actions (G-ll) using the ability to move is a combined function

of the cue generation (initiation of information that a threat is presente.g., alarm, smoke, word of mouth, etc.) (G - 12 )

;

the cue reception (the

transmission of the signal into understood and knowledgeable information to

the responding person or device) ( C - 1 3 )

;

the manner in which the person or responding equipment receives and analyzes that information and makes a safeguarding decision from it (the decision of concern is the safeguarding

action decision resulting in the degree of physical movement and the route of

such movement) (G-14); and finally, the actual physical act of movement (G15). The series of functional factors G-12 through G-15 are sequential in

occurrence

.

48
25

.4

Provide Protection in Place

Protection in place is defined as the provision of protection in the normal

work place or other location of the "exposed" without the necessity of

relocation to a specific area. Protection in place can include that type of

protection which is conditional on the location and degree of the threat

(i.e., a place may be appropriately protected when the threatening fire is

remote and/or barricaded but be unsatisfactory as a place of refuge with a different location or degree of fire exposure). For example, barricaded fires

in gob areas may leave the entire rest of the mine adequately protected in

place

.

The degree of success in providing protection in place is the sum of the

degree of success provided by safeguards that provide their protection

inherently without any special kind of fire action plus the degree of success achieved from safeguards initiated at time of fire.

26.5 Provide Inherently Safeguarded Place

Inherently safeguarded places are those that provide their protection without

the need for any adjustments at the time of fire. A prime example of this is a fixed fire resistive barrier. The degree of safeguarding of the place must

be sufficient to prevent harm, but the safeguarding may be either of a temporary nature whereby the place may have to be evacuated at some level of

threat or, the place may be designed to be tolerable for the duration of the

maximum possible threat. The degree of success is a function of this quality

and the level of threat.

This is an End Event in the Event Logic Tree as drawn.

26.6 Threat Initiated Safeguard

To the degree that safeguards are not inherent, they may be of a type that is

initiated at the time of fire. Prime examples would include automatic closing

barriers or the erection of temporary stops or barriers by miners. As with

49
the inherent safeguard, they may provide temporary or limited security or may

be designed to provide tolerability for the duration of the potential fire.

This is an End Event in the Event Logic Tree as drawn; however, in addition to

Functional Branch G (which applies to all of the events in this branch)

,

Functional Branch H outlines factors controlling the success of threat

initiated safeguards.

Functional Branch H. Threat Initiated Safeguards (Figure 14)

Active systems are fire safety systems that perform their function by

responding and performing in a different mode at time of fire than in their

normal non- fire condition. The functional requirements for such systems are that they must respond when called upon (H-l), and upon response must perform

their essential function (H-2). The functional control of response

capabilities are identical to those in the sub-branch, Response, of Functional

Branch D.

The performance requirements vary according to the type of performance

necessary but relate in each case to functional entities covered under threat

control such as Functional Branch F, where a barrier is expected to exclude

fire products; Event 15.4, covering the management of product movement; Event

15.5, covering control of oxygen depletion, etc.

25,5 Relocate "Exposed" to In-Mine Refuge Areas

Relocation to in-mine refuge areas involves emergency movement of the

"exposed" from their normal place in the mine to some safeguarded place. The

safeguard may provide temporary or duration of fire tolerability. The

functional requirements of both Functional Branches G and H apply.

This is an End Event in the Event Logic Tree.

50
25.6 Evacuate Mines

Evacuation is the removal of the "exposed" through a safe area external to the

mine. In terms of life safety, it is the primary means of protection of the

exposed. Functional Branch G applies in this case.

This is an End Event in the Event Logic Tree.

CHAPTER 13 - STATES AND TRANSITIONS

In recent years a combined concept of the interrelationship of people, the

environment, and fire has emerged. This concept was introduced by Nelson, in

terms of the fire environment in 1972 [1] and expanded by him to include the

interrelationships of fire and people in 1977 [2]. Elements of the approach

are fundamental to the Building Fire Model developed under the auspices of the

National Fire Protection Association [3]. The state - transition concept is

felt to allow better focus on the worth and impact of prevention, control, or protection strategies.

This concept is based on the premise that:

1. Within any given environment (mine, building, or other location), fire

behavior and the behavior of persons involved can be expressed as a series of describable behavior patterns connected together to form

sequences

.

2. The fire behavior and people behavior sequences are separate but can be

(and often are) inter- reacting with each other.

3. The separate behavior patterns that make up the sequence consist of

individual periods during which there is a consistency of the form of

fire growth and/or inter-play between fire and its environment, or of

the response of individuals or groups of individuals to the resulting

threat. These periods of consistent behavior are referred to as states.

In some texts, the terms "realms" or "regimes of burning" are also used

51
in reference to states of fire. In human behavior research, the term

"episode" is more commonly used than states to describe periods of human

behavior. The term episode is used for that purpose.

4. Each state (or episode) starts and ends with a change in response to the

environment of sufficient magnitude to cause a change in the patterns of

behavior. In the fire behavior sequence, these are referred to as critical events. In the human behavior sequence, they are referred to as decisions or decision points.

5. Many of the states of fire behavior are not static but vary with time in

the state. In such situations, the degree of threat or harm can vary

according to the period of time within the state. The rate of

variation, however, will differ from state to state. The fire behavior

sequence, as outlined herein, is such that generally an increase to a higher numbered state constitutes an increase in both the level of

threat and the rate of increase of threat for a period of time in that

state

.

6. At any instant in the combined fire behavior/human behavior sequence

there is a single overall level of fire safety performance (or

conversely fire risk or harm) . This level is represented by the top

event (Event 1.0, Fire Safety Performance) in the Event Logic Tree.

7. The fire safety performance is enhanced by the degree to which the fire

safety systems and efforts to maintain the fire in a lower order state

succeed, and the degree to which the period of advance into any more destructive or threatening state is limited. Similarly, those

objectives related to the well-being of persons are enhanced by the

degree to which the human behavior episodes or activities avoid the

simultaneous occupancy of a space by intolerable fire threats and

humans

.

8. The events in the Event Logic Tree govern the states that a fire is in,

the transitions between states, the advance within a state, and the

52
human behavioral sequence. In general only a portion of the events are operative in any state or involved in any transition. Those factors

that control the situation at any moment are referred to as dominant

factors for that state or transition. In general, the entry of a new dominant factor results in a state change.

Fire Behavior Sequence

The choice of states depends on the level of detail desired in examining the

fire condition. For the purposes of this study, six major states of fire have

been selected and have been sub-divided into their most important sub-states.

The six basic states are:

State 0, Non-burning

State 1, Development on First Ignited Fuel

State 2, Multi-item, Fuel-controlled Burning

State 3, Ventilation Controlled Burning

State 4, Multi- spacial Involvement

State 5, Mine Fire

a . State 0. Non-burning

This state covers all conditions when fire does not exist. The substates cover the range of conditions from the normal or static situation

where no fire threat exists through the varying levels of precursor

situations in which the potential of fire initiation increases through

heating or chemical reactions of potential fuel. The critical events or transitions from the non-burning state include the various types of fire

initiation that may occur. The actual transition from non-burning to a burning state may be defined differently under different circumstances.

Most of these circumstances are listed in the critical events for

transition from the state. It is considered legitimate to define fire

initiation by any of these critical events according to the needs of the user of the concepts. It is essential, however, that once such a

53
decision has been made that this working definition be maintained or that any variation be clearly identified.

The sub- states of State 0, Non-burning, identified for the purposes of

this paper are:

0.0 Static

0.1 Preheat/self heating

0.2 Vaporization (of hydrocarbons)

0.2.1 Lean

0.2.2 In explosive/flammable range

0.2.3 Rich

0.3 Pyrolysis (without combustion)

The critical events governing transition from State 0 include:

A.l Supported smoldering

A. 1.1 To State 1

A. 1.2 To State 2

A. 2 Self - sustained smoldering

A. 2.1 To State 1

A. 2.

2

To State 2

A. 3 Supported flaming

A. 3.1 To State 1

A. 3.2 To State 2

A. 4 Self-sustained flaming

A. 4.1 To State 1

A. 4.

2

To State 2

54
To State 0

A. 5 Explosion

A. 5.1 Non-disrupting

A. 5.

2

Non- disrupting

or 3

No subsequent ignitions - Subsequent ignitions to States 1, 2

A. 5.

3

Physically disrupting of spacial barrier - No

subsequent ignitions - To State 0

A. 5.

4

Physically disrupting of spacial barrier - Subsequent

ignitions, to States 1, 2, 3, 4 or 5

b . State 1. Development on First Ignited Fuel

This state covers the development of fire from the initiation of burning

to the point where the fire either terminates or extends to one or more additional items (or involves the entire mine or section of the mine in

a ventilation controlled fire). By definition, this state is relegated

to fuel controlled burning with little or no influence on the burning

item as a result of energy feedback from the overall surrounding

environment. In this state, not only the basic physical properties of

the material, but its shape and form and its proximity to other

ignitable material play important parts.

The sub -states of State 1, Development on First Ignited Fuel include:

1.1 Single surface spread

1.1.1 Single-dimensional

1.1.2 Two - dimens ional

1.1.3 Three - dimens ional

1.2 Multi- surface spread

1.2.1 Single-dimensional

1.2.2 Two - dimensional

1.2.3 Three-dimensional

1.3 Gas phase propagation

1.4 Steady state

55
1.5 Decay

The critical events involving transition from State 1 to an additional

state include:

B.l Ignition of additional item - fuel controlled burnings

B.1.1 Individual item(s) (separate fuel package(s)) - to

State 2 B.l.

2

Combustible surface(s) - to State 2 B.l.

3

Combustible gas /vapor/dust mass

B.l. 3.1 Non-disrupting - to State 3 B.l. 3.

2

Physically disrupting of spacial barriers - to State 4

B.2 Transfer to ventilation controlled burning - to State 3 B.3 Extend to multi -compartment burning - to State 4

B.4 Decay to State 0

c . State 2. Multi-item. Fuel-controlled Burning

This state is an extension of State 1 in which the critical event

involved has resulted in the spread of fire between items, increasing

the basic fuel bed in both quantity of fuel and extent, but has not

involved a change from fuel controlled burning or reached an intensity

that produces a significant energy feedback from the surrounding

environment

.

The sub -state of State 2 include:

2.1 Individual burning (repeat State 1 for item(s) 1 to N)

2.2 Coalesced burning (repeat State 1 for coalesced fuel package)

The critical events governing the transitions from State 2 to another

state include:

56
C.l Transfer to ventilation controlled burning to State 3 C.2 Decay to State 1 C.3 Extend to multi -compartment burning - to State 4

C. 4 Decay to State 0

d . State 3. Ventilation Controlled Burning

Ventilation controlled burning is that state of fire where the burning

rate is controlled by the rate at which the necessary oxygen for

combustion can be obtained an entrained in the effluent products

liberated by the feedback energy from flame, hot gases, or heated

surfaces to exposed fuel. The transition from fuel controlled burning

to ventilation controlled burning would normally be expected to force

evacuation of all or part of the mine and likely involve the coal seam.

The sub- states within State 3, Ventilation Controlled Burning include:

3.1 Steady pyrolysis rate

3.2 Decreasing pyrolysis rate

3.2.1 Constant extent of burning area

3.2.2 Decreasing extent of burning area

3.3 Increasing pyrolysis rate

3.3.1 Constant extent of burning area

3.3.2 Increasing extent of burning area

The critical events governing the transition from State 3 to another

state include:

D. l Inter-spacial ignitions - Extend to State 4

D.1.1 Unsupported discrete ignition(s) (apply State 1 or 2 in new spaces)

D.l.

2

Energy supported discrete ignition(s) (apply States 1 or 2 in new space(s))

D.l.

3

Massive energy supported general ignition (apply

State 3 to new space(s))

57
D.1.4 Structural failure (extend space to Include newly

included area(s))

D.2 Recede to fuel controlled burning of 1 to N items - to

State 2 D.3 Recede to fuel controlled burning of item - to State 1

D. 4 To State 0

e . State 4. Multi-snacial Involvement

Multi- special involvement covers the spread of fire from space to space

through unprotected openings or through failure of the fire stopping

capabilities of physical barriers. It is expected that advance of fire

into State 4 will usually involve ventilation controlled burning in the

exposing space. Sub- state 4.1 covers the situation of advance of only

ignition sources without transfer of the full energy or joining of the

newly involved spaces into a single coalesced fire. In such cases, fire

in the additional spaces develops relatively independently of the

initial fire. Sub- state 4.2 covers the situation of advance of a full

flame front where the additional spaces join the initial fire in one single ventilation controlled incident.

The individual sub-states of the State 4, Multi-spacial Involvement,

include

4.1 Separate burning (independent repetitions of states

1 through 3)

4.2 Coalesced burning (joining of burning spaces into single

coalesced fire)

The critical events marking transition to other states include:

E. l Transfer to mine fire - Extend to State 5

58
To State 3 To State 2

E.2 Decay

E.2.1

E.2.

2

E . 2 .

3

To State 1 E.2.

4

To State 0

f . State 5, Mine Fire

This state is defined as a fire which so involves the mine as to have

reached a steady state of burning and essentially driven all occupants

to the surface where the mine cannot be re-entered until the fire decays

in some manner to a lower level state.

Human Behavior Sequenced

The sequences of states or episodes of human behavior do not necessarily

follows progressively increasing levels of safety or potential of harm.

Rather they consist of actions chosen by those involved (as a result of

experience, training, or ad hoc judgement) that they believe best for their

needs or objectives at the specific time of decision. The basic objective in

protection of humans is always the avoidance of occupancy of the same space at

the same time by people and by conditions intolerable to people. In fire

situations, the fire effect may be moving or may be concentrated in a limited

area. The humans involved may or may not be mobile according to the

conditions they face and their safety may or may not be dependent upon their

actions. In some cases, they may be able to undertake actions to directly

mitigate the threat. In other cases, they may only be able to undertake

actions to escape or avoid the threat. The number and type of actions

undertaken by people in fire situations are manifold. The following general

classifications, however, are proposed as the episodes which can be used to

classify the physical acts under Functional Element C-15 of the Event Logic

Tree. For the purposes of this paper, these episodes are:

Episode A, No Action

Episode B, Investigate

59
Episode C, Attack

Episode D, Alarm

Episode E, Flee/Escape

Episode F, Rescue

a . Episode A. No Action

No action is used to define any situation where persons do not undertake

any activity relevant to protection of themselves or others or to

control of fire. Such actions may include continuing to mine or haul

coal, attending to other business, or undertaking some more pressing

need (e.g., maintaining life support ventilation to portions of the mine

unrelated to the fire)

.

b

.

Episode B. Investigate

Investigation includes all of those actions where a person receiving a cue seeks to remove ambiguities or to gain advice or instruction before

taking further action. Fire experience indicates that humans tend to assume that risk indicators are indicative of their lower, rather than

their higher potential. Often, they seek to remove ambiguities from

indistinct or confusing cues or signals, and tend to seek reinforcement

before taking unusual actions, even those potentially for their own or their fellow workers well being or for protection of the facility.

c . Episode C, Attack

This episode covers any activities aimed directly at terminating the

fire or controlling or mitigating its impact on either people or property. Specific actions would include activities such as,

application of extinguishment, closing of barriers to control smoke, or removal of fuel from a fire source.

60
d. Episode D. Alarm

This episode includes all of those activities in which the existence or the state of a threat is communicated by direct human contact, voice or symbolic alarms, or other means. The alarm may be given to warn of

danger, initiate self protection measures, summon emergency assistance,

or other purposes.

e . Episode E. Flee/Escape

This episode includes all activities directed at escaping the threat of

fire. It includes leaving the mine or taking refuge within the mine.

f . Episode F. Rescue

This episode includes all activities involved in assisting others. It

includes those in which a miner assists another in escaping or taking

refuge as well as the more formal rescue teams that may enter a mine

after the fire has developed to a more advanced fire state.

General Mode

Figure 15 outlines a general model of the interrelationships between the fire

behavior sequence and the human behavior sequence. As indicated by this

model, fire behavior is looked upon as a series of independent states

connected by critical events. Human behavior is a similar series of

independent episodes connected by decisions. The two sequences influence each

other with stimuli (cues) that flow from the fire behavior to the human

behavior sequence causing action or impacting on the well being of humans.

The flow of stimuli is caused by the fire behavior sequence and is

proportional to it but entirely separate in its functional aspects. Flow from

the human behavior sequence to the fire sequence is however, in the form of

impacting actions. The type of impacting action can be any of the behavioral

episodes that cause a change in the fire or the ensuing fire threat.

Impacting actions can be to the benefit of the overall fire safety performance

61
where they involve or result in intervention in the fire development.

Conversely, they can be detrimental to the objective where the actions result

in increasing the threat. Typical of such detrimental action might be the

opening of a door in or the breaking through stopping in a manner that either

diverts the air supply or allows smoke propagation to areas that would not

otherwise have been affected.

62
Figure 1 . General (overview) Event Logic Tree

- OR - Mutually exclusive (either or, but

not both|

- OR - Not mutually exclusive (either or, or both)

- OR - Multi variant relationship (i.e., probability density function) Conditional event is dependent on

both occurrence and magnitude ot conditioning event.

- AND Never mutually exclusive, success always dependent on all involved

events. Individual events may or may not be conditional on other events

• Function The performance of the above event is a function ot tbe subsequent elements. In this gate

the elements are parametric variables.

• Events proposed for future development

- Given ( 5.3) reads "given 5.3”

- Not | 5.3 reads “given not 5.3”

63
Figure 2. Control Fuel Availability Branch

64
Figure 3. Control Fuel Susceptibility Branch

65
Figure 4. Limit Igniters Branch

66
Figure 5. Limit Inherent Potential Branch

67
Figure 6. Control by Intervention Branch

68
Figure 7. Mass Product Threat Branch

69
Figure 8. Control Other Fire Threats Branch

70
25.1 LIMIT TO MlhLCCESS

E s

262

26 1 AT TIMES OF

AT ALL SPECIFIC CONDITIONS. TIMES THREATS. OR

POTENTIALS

24 1 LIMIT OR

EXCLUDE EXPOSED"

252 1LIMIT ACCESS OR 25 3 CONCENTRATION OF EVACUATE IN EXPOSED" IN CASE OF

SPECIFIC AREA POTENTIAL THREAT

OF MINE |251

5

263 264

AT TIMES OF

AT ALL SPECIFIC CONDITIONS. TIMES THREATS. OR

POTENTIALS

Figure 9. Limit of Exclude "Exposed" Branch

71
Figure 10. Safeguard "Exposed" from Given

Threat Branch

72
Figure 11. Functional Branches A and B

73
Figure 12. Functional Branch C

74
Figure 13 Functional Branches D E and F
Figure 14. Functional Branches G and H

76
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NBS-U4A (REV. 2 -80 ) U.S. DEPT. OF COMM.

4.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO. NBSIR-86/3502

2. Performing Organ. Report No.| 3. Publication Date December 1986

TITLE AND SUBTITLE

A Qualitative Analysis of the Inherent Fire Safety/Fire Risk in a Coal Mine

5. AUTHOR(S)

Harold E. Nelson

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

Gaithersburg, MD 20899

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

U.S. Department of Interior

Bureau of Mines

Pittsburgh, PA

10.

SUPPLEMENTARY NOTES

UU Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11.

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

bi bl iography or literature survey, mention it here) A quantitative description of a fire safety analysis sytem for a coal mine. An

event-logic tree and a state transition model are presented. This report is also

presented as Appendix D of NBSIR 86-3425, The Development of a Fire Evaluation System

for Underground Coal Mines.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Coal mines; event logic tree; fire hazard! fire risk; fire safety; state transition.

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

HU Unlimited

HU For Official Distribution. Do Not Release to NTIS

| Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 85

15. Price 20402. HU Order From National Technical Information Service (NTIS), Springfield, VA. 22161 $11.95