Ranking factors impacting 

survival during coal mine fires 

F.N. Kissell, RJ.Timko and Litton 

Abstract ___ This study ranks thefactors impacting 

a coal has been established that 

time delaysis the in saving 

Consequently.every event is in terms of 

its and the effectiveness of any action taken to 

is measured in of the time it 

By actions to time saved. these 

found that a comhination of actions was This 

combination was: 

installing lifelines. 

leakage and 

the

Changing leakage alone was much 

as was altering the CO monoxide), sensor alarm 

These results confirm an study on escape 

minefires. The study had shown that, with the 

exceptionof delays, changeshave minimal impact. 

Significant in fatalities only take place with 

changes. 

Introduction 

analysis is the important notion that timely action is the essential 

element to saving lives during a mine fire. This notion is 

supported in a recent fault-treeanalysisconductedby 

and Kissell (1 who found that reducing time delays during 

a mine fire was by far the most important factor in saving lives. 

Using this approach, the effectiveness of any action taken to 

improve survival is measured in terms of the time it saves. 

Objective 

is timefactors 

for fire conditions in underground US coal and if possible, 

determine where gains in survival are most achievable. 

Modification of equation 

US coal mines always have multiple entries. Thus miners 

will generally have the opportunity to escape through an entry 

adjacent to the one on fire rather than the onecontaining the fire. 

The important survival factors are how much air leaks from the 

fire entry and how long it takes the firetogrow to a sizesuch that 

the concentration of leakage smokeand fumesmakes the escape 

entry’ unusable. To indicate that it is the escape entry concentration that is being used, will replace 

Also, when the fire takes place at a location the 

working face, it is very probablethat workers must move toward 

may involve instrument performance, decision-makingunder uncertainconditionsandknowledgeof safety procedures. To reduce 

the hazard fires,thiseventchain must be asa systemof 

related events. By relatingtheseeventsmathematically,the

necessary for system optimization can be calculated. 

Roberts (1987)has devised a simple, yet very effective,way 

to relate the various events taking place during a mine fire. He 

viewed the system as resulting from a competition between the 

creation and circulation of toxic fumes and the withdrawal of 

workers. This competition is represented symbolically by: 

I = + - + + 

where: 

I = a survival index (rnin) for a specified fire situation and a 

specified miner. 

= time for a fire to grow in size to a toxic 

concentration of fumes in the ventilation. 

time (min) for fumes from the to circulate in the 

ventilation to the point of escapefrom the contaminated airway. 

= time (rnin) for fire detection. 

= time interval (rnin) between fire detection and the 

beginning of worker withdrawal. 

= time (min) for a worker to travel from his original 

location to a point of escape from the contaminatedairway. 

= 

Increasingly positive values of I represent safer conditions. 

The essence of the Roberts’ approach is that every event is 

measured in terms of the time it takes. Implicit in this simple 

and aroundthe fire to reach fresh air. Sincethis involves passing 

close by the fire, then =0. With these changes,the modified 

equation is: 

I = - + 

This study’s approach will to evaluate the time saved by 

various actions taken to improve survival during fires. A 

comparison of these times should then show the relative effectiveness of the various alternatives. 

Estimating contaminant levels 

Foran estimationof contaminantlevels,it isassumedthata 

by the US Bureau of Mines during testing 

(Litton, and 1991). Figure shows growthof 

a fast-growingbelt fire during these Thechange in 

~~~ 

I This term “escape entry” is chosen since the exit route may or be 

the officially designatedescapeway.

In this test, 320 (705 of coal were ignited by electrical strip heaters. 

The burning coal then SBR The 

air velocity during the test was 1.25 (250 

F.N. Kissell, R.J. Timko and C.D. Litton are research supervisor, 

physicalscientist and supervisoryphysicalscientist, respectively,with 

the US Bureau of Mines, Pittsburgh,PA. 
-

I 

E 

0 

-

0 20 

Time from start of flame,min. 

Fig. 1 -Downstream carbon monoxide and smoke density levels 

during the growth of a typical SBR test fire. 

optical density is also shown since the visibility loss due to smoke 

impactsthe ability toescape. Kissell and (1992)have shown 

that seriousvisibility impairmentcantake place longbefore

concentration the toxic level. 

Escape through the adjacent entry 

The data shown in Fig. only apply to the entry on fire. The 

contaminantconcentrationin the adjacentescapeentry dependson 

the sizeof the and theamount of leakage. For instance,if is 

the the airway to the escapeentry,and is 

the original amount of airflowing in theescape entry, then: 

= 

where and are the contaminant concentrations in the 

escapeentry and the fire airway, respectively. Using this simple 

dilution equation for a given leakage,a determinationis sought 

regarding what concentrationsof smoke and CO in the leakage 

from the fire airway will produce unacceptable conditionsin the 

escape entry. Unacceptable conditions represent the point 

beyond which escape is unlikely. 

For example,suppose =9.4 cfm). For CO, 

irritationfrom SBR was 

found (Kissell and 1992)when themeasured was only 

ppm. Thusthis CO was selectedasrepresenting 

in is4.7 

cfm), then theleakage ratio + =0.333. 

Using thesevaluesin in thefireairwayis From 

' The total leakage is that through many stoppings, not through a single

stopping. Thekey assumption in this analysis is that air leaksfrom the entry on fire to the escape entry. This type of leakage generally occurs and Derick, 1989). Kissell 1991) have investigated the impact

of checking off the intake escapeway to raise its air pressure during an evacuation. 

140 

I 20 

100 

80 

60 

- 40 

20 

--- CO criterion 

smoke visiblllty 

available 

from change in leokaqe 

1 -

--- CO criterion 

smoke visiblllty 

I I I I I I I 

I 2 3 4 5 20 

8 

E 

Leakage, 

L I I 1 1 1 1 1 1 

.94 2.4 4.7 9.4 

Leakage, 

I I I l l t i I 

'33 0.5 

Fig. 2 to reach unacceptable conditions in the escapeway vs 

leakage. Each represents a different criterion. 

Fig. this CO is reached in 34 min. 

Different leakage values may be selected. Also, this simple 

dilution appliesto the smoke concentrationexpressed in optical 

density units. In the escape entry, unacceptable visibility is 

reachedatanopticaldensityof0.2 and Newman, 

to3.7-m Ifaleakage 

of 0.94 cfm) is selected, then = 0.091,and the optical density in the fire airway (and leakage air) 

is Figure 1 shows that an optical density of is 

reached in 28 min. 

By repeating this calculationscan be made forthe 

time it takes to contaminatethe escapeentry at differentleakage 

levels and for several different contamination criteria (Fig. 2). 

For example, with a ( leakage + = an escapeentry visibility of 3.7 m (12 ft) is reached 

in 19min, a CO concentrationof ppm is reached in 34 

and a COconcentrationof 1500 is reached in 92 min. Each 

of these contamination criteria represents obstacles to a safe 

withdrawal. The strategy is to deal with the most restrictive 

obstacle (the smoke) first. 

Fire safety alternativesfor increasing 

The alternatives for increasing include: 

reducing air leakage, 

Measuring sensory irritation in the equivalenr is 

not entirely satisfactory. Hopefully, future research will establish better 

ways to measure sensory irritation and toestablish appropriate more objectively. ' 1500 is the critical CO level (Tewarson and Newman, 198 Kissell 

and Litton, 1992).

Lifelines are ropes installed in intake and/or return escapeways to guide

miners through dense smoke. 
I I I I 

KEY I 

CO... 

(visibility 

I 20 - ... 

smoke criterion 

FG ...... Fire of 

Firs 

80 

- 56 available 

leakage and 

60 

E 

40 

20 

9 minutes available 

I I 

I 5 6 78910 20 

Leakage, 

I I 

.94 2.4 4.7 9.4 

Leakage, 

I I I I I 

.33 0.5 

growth to 

Fig. 3 - of fire growth added to Fig. time to reach 

unacceptable conditions in the escapeway vs. leakage. 

providing lifelines6 and 

reducing the fire growth rate. 

Figure 2 is useful for showing how much time these save. 

Reducing leakage 

As (3)indicates, the contaminantconcentration depends 

on the leakageamount. The objectiveis then to relate a leakage 

change to an amount of time saved. To do this, an escape 

criterion must be selected. For instance, since the lack of 

visibility is the most restrictive obstacle and most mines do not 

have lifelinesthat permit travel through dense smoke,the 3.7-m 

isemployedasthepointbeyondwhich 

escape is unlikely. With leakage into 

the escapeentry, 3.7-m 2-ft) visibility arrives in rnin (Fig. 2). At 

leakage, the equivalent time is 28 Thus under this set of 

conditions, the 80%decrease in leakage has saved only 9 min. 

Providing 

for travel through smoke when the visibilitydropsbelow 3.7 m (I 2 

ft). When the3.7-m 

can bedropped. Then the next most be used, 

thesensory Likebefore, 

at a leakage of 4.7 cfm), 3.7-m visibility is 

reached in rnin. At thesame leakage rate, however, thesensory 

initation limit of ppm CO is reached in 34 min. Thus, lifelines 

have saved an extra 15min. 

Figure 2 also shows the 60 rnin saved by the combinationof 

lifelines and a self-contained (SCSR) device. 

But since much of this time extends into the range of severely 

restricted visibilities and severe sensory irritation, factors like 

panic and confusion (Jin, 198 could impede escape7. 

rare 

Reducingthe fire growth rate also savestime. Lower growth 

rates may be achievedby reducing the flammabilityof materials 

used in mines and by removing loose coal that collects on the 

mine Inthebelt fire tests used tocollect the Fig. I data, 320 

wereplaceddirectly underthebelt. This 

coal was then ignited by electrical stripheaters (Litton,

and 1991). 

A 320-kg (705-lb)pile of loose coal under the belt could be 

a “worst case” test. Thus, it is important to assess the impact of 

lower fire-growth rates that might result when less loose coal is 

present. This would indicate the importance of removing loose 

coal accumulationsfrom fire sources. 

The lower fire-growth rates were set at 50% and 25% of that 

shown in Fig. I. It is assumed that the entire curve shifts 

downward by the same In Fig. for example, the 

CO concentration at rnin is 860 So at 50%and 25% 

growth rates, the COconcentrationsat rninwould be 430 and 

2 ppm, respectively. 

In the same manner, the optical density curve shifts downward for every time value, and Fig. 3 shows how much time is 

saved by these revised growth rates. In every instance, the 

criterion curve is shifted upward; a slower-growingfire means 

that it will take longer to reach either the 3.7-m (12-ft)visibility 

limit or the ppm limit. Using the 3.7-m visibility 

criterion as the most restrictive obstacle and assuming a 

leakage,only 9 rnin are saved by reducing 

the fire growth rate to 25% of that shown in Fig. 

Analysis of 

Without lifelines, the 3.7-m visibility criterion must be 

used asthe point beyond which escapeisunlikely. An examination 

of Figs. 2and3showsthat when this isused, 

the fur:safety alternatives save little time. Forexample, 

leakage 4.7 to cfm) 

saves only min (Fig. the fixed at 4.7 

reducing thefire growth rateto 25% of that shown in 

Fig. also savesonly 9 min (Fig. 3). 

The problem is that with any leakage into the escape entry, 

smoke contaminationoccurs so early that none of the obvious 

alternatives by themselves saves much time. Although using 

lifelines alone will save about min (Fig. this, by itself, is 

not much. However, by using lifelines, the 3.7-m (12-ft) 

visibility obstaclecan be bypassed and the less restrictive 

ppm CO criterion can be applied. With this new criterion, 

reducing the leakage or fire growth rate has more impact. 

Furthermore, with lifelines, the SCSR device can be used. 

Note, also, that a combination of the alternatives has a 

synergisticeffect in that the impact on time saved is 

’ Note that even at ppm the smoke isalready thick enough to prevent

the miner from seeing ground. Also, other limitations may arise, like 

the improper donning of the SCSR. This may include either failing to 

isolate the lungs (Kovac. and Bmich, or goggles

improperly and ’ 

Belt fires, as well as other mine fires, go through different stages that 

involve burningdifferent Action taken will 

involve some materials more than others and thus affect the 

rate curve unevenly. For example. at 25%of the fire growth rate, the time 

thebelt 

be less. 
---- 

tive rather than additive. Figure 3 shows that 56 min are saved 

from lifelines in combination with 50%of the leakage and 25% 

of the fire growth rates. While the sum of these individual 

changes is only 28 min, the synergistic effect produces a total 

time saved that is double the sum of the parts. Similar results 

were obtained in anearlierfault-tree study conducted by Goodman 

and (1989). This earlier study found that with the 

exceptionof delays, single-factorchanges had minimal impact. 

Significant reductions in fire fatalitiesonly with 

tiple-factor changes. 

Fire safety for decreasing 

Decreases in (the fire detection time) will result in an 

improved survival index. For conveyor belt entries, estimated 

detection times may be obtained from a recent study conducted 

by Litton, Lazzara and Perzak (1991). They continuously 

measured fireproductsin the airasa pile of coal under a belt first 

smoldered. broke into flame and then set the belt afire. The 

purpose was to establish appropriateCO, sensor alarm thresholds, given factors such as detector spacing,entry size, airflow 

and detection time. They assumed that the alarm is initiated by 

COfromthe coal fire that precedesthe belt ignition. The 

relevant equations (Litton, Lazzara and Perzak, 1991)are: 

where: 

= time required for the sensor alarm threshold 

CO, to be reached at the fire, 

CO, = sensor alarm threshold (ppm). 

V, = air velocity 

B, =entry area = a production constant relating the 

amount of CO produced to the air velocity, and 

a,, relatingthefiregrowth 

flaming coal fires to air velocity. 

where: 

= total time for fire detection (min), taking into 

account the transport time from the fire location to the sensor 

and the sensor response time; 

I, = sensor spacing and 

= sensor response time, assumed to be min. 

The in the transport term results from an assumption that 

the average fire is halfway between the sensors. 

Sensor- setting 

Assume that = 10 (I 08 = 0.5 (100 

and I, = 305 m ft). From Litton, Lazzara and 

Perzak B = 4.5 and a,, = 2.1. These authors also 

selected a flaming-coal-firedetection time of = 14.25 

For this detection time, the recommended sensor alarm 

threshold, from the above equations is 15.4 

The question is, how much time would be saved by a lower 

sensor setting of 10 ppm? Using CO, = 10ppm in the above 

equations, = 1.4 min, a savings of about 3 min. 

Recommended value of 

from RI 9380 

T i i 1 1 1 i i T 

2 4 6 8 16 

Sensor alarm threshold Fpm 

Fig. 4 -Time saved or lost by changing the CO, sensor alarm 

threshold. 

Figure4 gives the time savedand lost by loweringand raising 

the CO sensor settings. These data are provided for three 

different air velocities: 0.5 2.0 

and4.0 (800 The impactof sensorsetting 

changes is slightly greater at higher air velocities. 

Note inFig.4 

a 6.4-min time loss. Similarly, the 2.0 curve does not 

extend beyond a 2-min time loss. These limits on the time lost 

occur because the belt catches fire after the recommended 

alarm threshold is reached. When the belt catches fire, the fire 

growth rate is much greater. Thus within the next minute, 

enough CO is produced to alarm any sensor set at or below 15 

For example, suppose the air velocity is 4.0 (800 

From Litton, Lazzara and Perzak (1991, Fig. (the 

average time between coal ignition and SBR belt ignition)is 18 

min. An additional minute is added to the belt ignition time to 

achieve a burning rate sufficient to alarm any CO sensor. Also, 

another 0.64 rnin is required for the time, and min is 

necessary for the sensor to respond, as indicated by the above 

equation. Thetotal isthus20.64min. Comparingthisvalue with 

the 14.25 rnin necessary for the sensor alarm threshold to be 

reached, it is obvious that the high CO levels from the burning 

belt reach the sensor only 6.4 rnin after it alarms from the coal 

fire. Then, if the sensor alarm threshold is raised above the 

recommended 4 ppm, the time lost will not exceed 6.4min. At 

2.0 a similar approach gives a maximum 

time of 2 min. 

Sensor- spacing 

The time lost or gained from sensor spacing changes is 

(5). For 

example, if V, =0.5 and the sensorspacing 

1, is 610 m ft). then = 10.2 If 1, is 

reduced to 305 m ft), then theequivalent time is 5. I min, 

for a time saved of 5.1 At higher velocities,the time saved 

‘I The value was selected by Litton, Lazzaraand because 

theirtestingshowed theaverage timebetween flaming 

coal ignition. Whetherthe 14.25-min detectiontime isappropriate

is disputable. However, even if a different time is selected, it will not 

change the conclusionsregarding the impact of sensor setting changes. 
Table 1 -Time saved or lost by different detectors during an 

underground belt-fire test (Dobroskiand Conti, 1991).The 

ppm CO detector provides a baseline,and the air velocity was 

0.633 (127

Alarm Time saved (min) Time lost (min) 

Smoke sensor 3.7 - Fiber optic 3.5 - 5 3.5 - CO, 2.0 - CO, 15ppm - - Thermocouple 10 ft fire with: 

C rise - C rise - 5. 7 

9.8 

by a closer sensor spacing is much less. 

Substitution of CO detectorsfor heat sensors 

The average alarm time for point-type heat sensors in USBM 

testing and 1991) is minutes for an 

air velocity of 0.5 (100 and an entry area of 7.53 

(81.1 For a more realistic entry area of 10

the alarm time is 22 min. Since the detection time for the 

recommended CO sensor settingswas 14.25 min, it follows that 

substitutingCO detectors saves about 8 At 2.0 

substituting CO detectors saves about 16 min. And at 

4.0 (800 it saves about 30 minutesi0. 

Multiple detector test 

Dobroski and Conti (1991) have measured the response 

times of several different detectortypes during an underground 

belt-fire test. The air velocity during their test was 0.633 

27 Using the CO detector as a baseline, the 

times or saved by the other detectors are shown in Table 1. 

These values areconsistent with this analysis. That is, at the fire 

growth rate given by Fig. 1, sensor settings have little impact 

when compared to the alternatives. 

Fire growth rate and sensor settings 

In section that examined alternativesfor increasing it 

was found thatalowerfire-growthratecouldenhancethe impact 

of the otherfactors. As aresultof thissynergism,the total impact 

of multiple changes could be greater than the sum of the parts. 

In this regard, it is useful to look at the impact changing sensor 

settings has with the lower fire-growth rates more typical of an 

average belt fire. 

in rates. 

For example, if the firegrowthrate is 25% of that shown in 

then isalso25% of that shown. Also,for agiven valueof CO,, 

the change in is also four times In Fig. when 

was 0.5 reducing the sensor setting CO, 

15.3to ppm saved3 rate is to 25% 

of that shown in Fig. =0.525 instead of 2.1 thetime saved 

is 

Fires in entries 

It is difficult to quantify the fire detection in entries 

where no fire detection system is used. In such areas,reliance 

is instead placed on the observations of those working underground. Given no clear way model this, only assume 

that the time required afiredependsonthevelocitywith 

which the smoke and fumes spread through the mine. For 

example, if the smoke and fumes must travel 1525 m ft) 

for the to be detected, at an air velocity of 0.5 

are required. With a air 

velocity,however,only 10 are required. The 50-min value 

is considerable when contrasted to those times associated with 

the other factors. 

Analysis for 

Fires in belt entries 

The impact of sensor settings was small when the airflow in 

the belt entry was low. But when the airflow was high, sensor 

settingsbecameslightly more important. Also, at moderate and 

high airflows,the substitutionof COsensorsfor point-type heat 

detectors can save a considerable amount of time. The impact 

of CO sensor spacing, however, is only significantat very low 

air velocities, as one might expect. Like before, the fire growth 

rate is important, and the sensor setting becomes more criticalas 

the fire growth rate diminishes. 

Fire in other entries 

It is difficult to make generalizationsregarding areas where 

fire detection systems are unavailable. Onecan say, however, 

that unattended equipment located outby is more hazardous 

when the air velocity is low. 

Fire safety alternativesfor decreasing 

is the time interval between fire detection and the beginning of worker withdrawal. Timely notification procedures for 

those underground must begin immediatelywhen fireis discovered. The review of published coal-mine-fire reports revealed 

that the two fire-related disasters of the past 20 years 

claimed 36lives. In both accidents,personnel on the surfaceand 

outby the fire had knowledge of the fire but delayed the 

withdrawal order. 

Survey 

Assigning a numerical value to is because of the 

variability in how and when withdrawal orders are given. An 

informal survey was conducted in which safety personnel from 

10 mining companies were asked to describe the 

making process that typicallyoccurswhen smoke isdiscovered. 

Theonly provision was that they assumeasmoke located 

outby the working face in an intake entry where miners would 

not normally be working. 

Most of the mines surveyed have CO detectors in the belt 

enmes. Somesystemsaremorecomplex and include dual-level 

CO alarms. For additional protection, some mines also locate 

detectors in intake and return entries. 

The survey responses varied from immediate withdrawal to 

a process where an initial warning is followedby an exploration 

to determine the exact location before a withdrawal order is 

issued. The person conducting the exploration evaluates the 

situation and determines whether withdrawal is necessary. 

'" the fire grows more slowly than that shown in Fig. the relative ranking

of some alternatives can shift. data show how lower fire-growth rates can increase the by changes in 

and (personalcommunication) have conducted studies on lowergrowth rate in which the time saved by substituting 

for conventional heat sensors was min. 
--- 

--- 

Although this places the responsibilityon someone more likely 

to have firsthand information, it may cost time. 

In mines having dual-stage alarms, a first-stage alert typically prompts the dispatcher or a section supervisor to send 

someoneto investigatethe cause. When the second-stage alarm 

sounds,the withdrawal to a point outby is begun. Inother mines, 

the withdrawal order is given as soon aselevated CO is discovered at two detectors in the same aircourse or if CO values 

remain elevated during consecutive samples. Most of the 

officials surveyed had fire-fightingexperienceor are currently 

mining in conditions prone to spontaneous heating. 

Everyone emphasized the importance of rapidly notifying 

those underground during a fire-related emergency. The problem some have with issuing immediate withdrawal orders is that 

once miners leave the working section, the ability to gain 

additional fireisoften lost. Moreover, 

the possibility of fighting the fire and preventing its spread is 

lost. 

In most of the surveyed mines, the requirement for supervisory approval to start a withdrawal has been dropped. Withdrawal orders are most often given by someone located on the 

surface, usually a dispatcher or a warehouseman. 

Comnzunications 

Roberts' equation implicitly assumes that communications 

are always maintained during the early stages of a fire, when 

withdrawal orders are likely to be given. If the fire destroys the 

telephone system, however, the time lost can overwhelm the 

other factors. It is thus useful to examine the location of phone 

wires near outby fire sources and ensure they are maintained at 

a considerable distance from these sources. 

Fire safety alternatives for decreasing 

is the travel time to reach a safe location outby a fire. 

Following a withdrawal order, some miners automatically head 

for the primary escapeway. They believe that because this 

escapeway is isolated, it will remain free of fire 

However, recent research and 1992)has shown 

that if leakage occurs,even very low levels can reduce visibilities and make travel difficult. 

Rail vehicles 

location depends on the type of 

employed. isusually 

anotherentry,isolatedfrom thehack. Theprimary escapeway isan 

Minerscan

path to walk the until outby the

A timesaving escapemethod involves riding a vehicle outby 

as long as the visibility is adequate. One possible visibility 

minimum would be the ability to see in the crosscuts. 

When the visibility becomes marginal,miners can abandon the 

vehicle,proceed to anotherairway andcontinue the withdrawal. 

Other criteria could be equally valid. 

Rubber-tired vehicles 

When the mine uses rubber-tired vehicles, the intake 

escapewaycan be the sameentryasthe vehicle travelway. Thus, 

withdrawalby vehicle is more likely in mines using rubber-tired 

transportation since miners will already be located in the intake 

escapeway. When visibility restrictions occur in this entry, 

withdrawal can become more difficult. Herethe onlyalternative 

outby fire,m 

300 2100 

2 3 4 5 6 7 9 

Distance until outby fire, 

Fig. 5 -Time saved or lost by riding vs. walking in various entry

heights. 

is to abandon the vehicle, enter another airway and begin 

walking outby. 

Studies have been performed on walking speeds in various 

entry 1986). These (24 

in entries less than0.76 m (30 in) high toabout I 

(300 in entries with heights greater than 1.8 m (72 in). 

The time saved by riding vs. walking,asseen in Fig. 5, depends 

heightoftheseambeingmined. 

mph) vehicle speed is used, and no visibility resmction is 

assumed for either walking or riding. 

Ranking of fire safety alternatives 

For fires with a growth rate similar to Fig. 1 an overall 

ranking of alternatives for all of the T factors is as follows: 

More than 30 min saved 

0 Installing lifelinespermits one to bypass the 3.7-m 

visibility criterion and allows SCSRuse. Thus up to 

are saved, subject to limitations(for example, if 

the SCSRis notdonned properly or duetodense 

smoke). 

In those instances with considerablesynergism, the application of multiple alternatives can yield savings. 

The example given used lifelines, in with a 75% 

decrease in the rateanda in leakage, 

to yield 56 saved. 

Riding vs. in entries 1.2-m (48-in.)high. 

I0 - 30 saved 

lifelines. 

Shortening the withdrawal decision chain. 

Ridinga vehicleinsteadof walkingin over 

in.) high. 0 CO forconventionalheat sensorsat all 

except low-air-velocitybelt areas. 

than min saved 

0 Ventilation changes. Even large ventilation changes had 

a surprisingly low impact. for this was that for the 

examplegiven,the visibility 
in a very short time (only min). Changes in this baseline, 

even if large on a percentage basis, do not yield much in the 

way of absolute time. 

in firegrowth rate. By itself, a 75% decrease in fire 

growthsavedonly low9 However,combined 

withotherfactors, Also, itwasshown 

that lower fire-growth rates will magnify the impact of reducing

theSensor settings. 

0 Adjustment of CO sensors.

Conclusions 

This study indicates that significant improvements in mine fire 

survival can be gained by a few relatively simple measures. In 

priority order, theseare: 

* Install lifelines. 

a major impedimentto safe withdrawal. Without lifelines,there 

are not many ways to gain improvements. 

Checkthatphone 

Pay very carefulattention to theremoval of loose coalat belt 

drives and points. Suchactioncan lowerthe growth 

rate, which has many synergisticbenefits. 

At all belt areas, thosewith low CO 

sensorsinstead of thermaldetectors. 

Shorten the decision Decisions must be based on informationcollectedwithin a shorttime 

0 minerstowithdraw thesection with avehicleas

as thevisibility is adequate. 0 Minimize leakageair whenever practical. Note that a deliberate attempt leakagego in a specificdirection involves 

some assumptions as to where thefirewill be. 

Be aware that an outby fire source not protected by an 

alarm system is more hazardous if in an airway 

with a low air velocity. 

Note that these conclusions basedsolely on theconsidemtion 

of time gained or lost. Other that might modify these 

priorities, such as instrumentation reliability, were not considered. 

In this study, it was assumed that thefire takes place in abeltentry, 

primarily becausethedata on fire growthand products 

were readily available. Nevertheless, these feel that the 

conclusions are generally applicable to any outby fire that grows 

quickly.

belllines.' 6th Mining and 

Pittsburgh. PA, June Hunter 13 

G.V.R., and F.N.. 

coal mine lire?.," SME. CO, Vd. 

T.. Studies in smoke fires.' Fire and 

Vd. 

and C.D.. smoke coal mine 

No. 1. 

F.N.. and R.J., intake 

to reduce smoke," US Mine 

June SME, 

J.G., C., and M.J., a mine

wearing a USBM 

C.D.. C.P..and F.J., 1991. conveyor entries: 

Mine and Congress, -. Chamber Mines 

Johannesburg. 13

J.L.. "Mine Mine Health and Academy, 

A., and J.S., 1981, the hazards 

with timber sets mines,' in and Nonmetal Mine Fire 

USBM 

fire in an underground mine," ' 4th US Mine . 

co. 48-56.