1 

Evaluation of deep-seated crib block fire tests 

M.A. Trevits 

National Institute for Occupational Safety and Health, Pittsburgh, Pennsylvania, USA 

A.C. Smith 

National Institute for Occupational Safety and Health, Pittsburgh, Pennsylvania, USA 

J.E. Urosek & M.P. Valoski 

Mine Safety and Health Administration, Pittsburgh, Pennsylvania, USA 

ABSTRACT: The National Institute for Occupational Safety and Health (NIOSH), in partnership with the Mine 

Safety and Health Administration (MSHA), is conducting research to test, evaluate, improve or modify coal mine 

fire-fighting strategies and methodologies through large-scale tests. Since wood is the second most abundant fuel 

available during a coal mine fire, it was decided that series of large-scale wood crib fire tests were needed to 

measure the products of combustion and to observe the capability of commonly available direct application fire 

suppression equipment, namely, fire extinguishers, water and gas-enhanced foam. This paper discusses the wood 

crib fire tests, provides insight into the products of combustion and describes observations made during the 

application of the fire suppression agents. 

Introduction 

In 2001, NIOSH and MSHA initiated an informal research 

partnership to develop new insight into the characteristics 

of mine fires and the limitations and capabilities of remote 

mine fire suppression technologies. Since that time, it is 

believed that this partnership has served the mining 

industry well as NIOSH and MSHA have worked together 

in the field at actual mine fire sites and in the laboratory 

and each have gained new insights into the science of mine 

fires and fire control and suppression technology. 

In late 2006, NIOSH began a new research project 

called “Remote Methods for Addressing Coal Mine Fires”. 

The objective of this research project is to test, evaluate, 

improve or modify remote fire-fighting methodologies for 

coal mine fire control and suppression and to directly 

transfer these improvements and modifications to the coal 

mining industry. The research is focused on the completion 

of testing of remote mine seal technology (including the 

evaluation of rigid foam technology), and the evaluation of 

fire suppression technology. The work plan calls for largescale, controlled deep-seated (firmly established) coal fire 

tests to be conducted underground in the NIOSH Lake 

Lynn Experimental Mine. A series of large-scale, deepseated wood crib fire tests was added to the work plan 

because the use of wood is so prevalent in underground 

coal mines. It was thought that the wood crib fire tests 

would yield significant information about the combustion 

products of wood components that are typically consumed 

in a mine fire and could offer a platform for evaluating the 

capability of directly applied fire suppression technology. 

Previous research was conducted by the U.S. Bureau of 

Mines on wood crib fires in an intermediate-scale fire 

tunnel (Egan and Litton, 1986). The previous work 

involved various Douglas fir crib block configurations and 

generated critically important information on carbon 

monoxide (CO) and carbon dioxide (CO2) gas 

concentrations, smoke particle characteristics, and heat 

release rates. The present study serves to expand and 

supplement the previous work using large-scale mixed 

wood species crib block fire tests because this material is 

regularly used in underground coal mines. 

2 Objective and Approach 

The objective of this study was to conduct a series of largescale, deep-seated, wood crib fire tests to measure the 

various combustion products and to observe the capability 

of commonly available direct application fire suppression 

technology, namely, fire extinguishers and water and gasenhanced foam. 

3 Fire Suppression Facility 

The crib block fire tests were conducted at the Fire 

Suppression Facility (FSF) and MSHA provided 

supplemental gas monitoring equipment for the tests along 

with technical experts to operate the equipment. The FSF is 

part of the NIOSH Lake Lynn Laboratory (LLL) which is 

located approximately 97 km (60 mi) southeast of 

Pittsburgh, Pennsylvania. The LLL is a world-class, highly 

sophisticated surface and underground facility where largescale explosion trials and mine fire research is conducted 

(NIOSH, 1999). 

The FSF was configured to simulate a 45.7-m (150-ft) 

long mine entry. The interior height of the simulated mine 

is 2.2 m (7.2 ft) and the width is 5.5 m (18 ft). The roof of 
 

 

 

 

 

 

 

 

Figure 1. FSF typical set-up for a crib fire test. 

the simulated mine is made of corrugated steel bridge 

planks, the ribs are made of solid concrete blocks and the 

floor is made of reinforced concrete. The interior roof is 

covered with a layer of specialized fire resistant mixture of 

vermiculite and Portland cement and a 2.5-cm (1-in) thick 

layer of this material has been placed on the ribs. A 1.8-m 

(6-ft) diameter, variable speed, axivane fan (equipped with 

a pneumatic controller to adjust fan blade pitch) has been 

installed at one end of the simulated mine to provide 

ventilation for the facility (blowing sustained airflow up to 

about 350 m/min (1150 ft/min) over the cross-section of 

the entry). The FSF is equipped with an array of chromelalumel thermocouples (type-K) located at 3-m (10-ft) 

intervals starting about 3 m (10 ft) from the fan leading 

along the centerline to the end of the simulated entry. The 

thermocouples are connected via a wire network to a 

computer-based data acquisition system. During the crib 

fire tests, data was collected at 10-second intervals and 

radiation corrections were not made in the temperature 

data. Video images of the tests were recorded using a 

camera that was positioned on the one side of the mine 

entry about 6.4 m (21 ft) upwind from the crib block sets. 

The components of the fire gases were measured using 

three gas monitoring arrays. The first was a 9-point array 

located 6.5 m (21.2 ft) from the trailing edge of the crib 

block sets. The array consisted of an interconnected 

network of black iron pipe set across the width of the mine 

entry. A total of nine holes were drilled into vertical 

sections of the pipe to sample the fire gases. The holes in 

the pipe were spaced equally apart from the roof-to-floor 

and across the width of the entry. A thermocouple was also 

positioned at each gas sampling point to measure the 

temperature of the fire gases. The gases collected at each 

sample point were mixed together in a manifold that 

penetrated the FSF roof. The manifold was connected to a 

tubing line that led to a MSHA Gas Monitoring Truck. 

The second gas sampling array was configured in the same 

manner as the first and was located 29 m (95.5 ft) from the 

trailing edge of the crib block sets. The third gas sampling 

array was positioned near the second gas sampling array 

and consisted of 4 holes drilled into 2.5-cm (1-in) diameter 

black iron pipe (spaced equally from the roof-to-floor). 

The pipe was positioned vertically at the centerline of the 

entry and was connected to a line that led to a set of 

NIOSH infrared gas analyzers. The gas analyzers measured 

oxygen (O2), CO and CO2 gas concentrations and the 

resultant data was collected at 10-second intervals and 

recorded by a computer-based data acquisition system. 

In the MSHA Gas Monitoring Truck, the gas samples 

were analyzed using a combination of infrared and 

electrochemical gas analyzers (the gases analyzed included 

O2, CO, CO2 and methane (CH4)). Throughout each test, 

the data from the MSHA gas analyzers was collected at 2­

minute intervals and was recorded in a computer database. 

In addition, gas samples were collected periodically over 

3- to 4-minute intervals from the first gas sampling array 

and were analyzed using gas chromatography. The gases 

analyzed included hydrogen (H2), O2, CO, CO2, CH4, 

acetylene (C2H2), ethylene (C2H4), and ethane (C2H6). The 

gas chromatography data was verified by back-up gas bag 

samples that were periodically collected from the same 

sample point and analyzed using a different chromatograph 

at a MSHA laboratory. 

The layout of the FSF for the crib block tests is shown 

in figure 1. The crib blocks were located 15.8 m (52 ft) 

from the fan and 10.4 m (34 ft) from a simulated conveyor 

structure in the FSF. The crib block sets were placed 0.5 m 

(1.5 ft) apart and were positioned near the center of the 

entry. As mentioned previously, the crib block sets were 

constructed on solid concrete blocks and located in the 

middle of the blocks was an impinged natural gas burner. 

The burners were set on the floor with the jets positioned 

below first row of crib blocks. Natural gas was used 

instead of an accelerant (e.g. diesel fuel) to assist in 

starting the fires because it was more readily consumed by 

the fire and left no residue that could have altered the wood 

fire combustion products. A series of preliminary 

experiments showed that the natural gas burners would be 

needed for about 50 minutes to ensure that the crib fires 

would burn without the need to re-light the burners. Prior 

to igniting the fires, the ventilation flow rate was measured 

in front of the crib block sets, at the first gas sampling 

array and at the location of the second and third gas 

sampling array. The ventilation air flow rates were 

measured at nine points in the cross-sectional area of the 

mine entry and an average flow rate was determined. 

4 Crib Block Composition and Crib Set Geometry 

The crib blocks were comprised of a variety of mixed 

hardwood species including beech, cherry, maple, white 

and red oak and poplar. In order to insure that the crib 

block sets would burn evenly and produce a more intense 

fire, the crib block sets were composed of an even mix of 

older blocks (about 6 to 8 months old) that had been stored 

underground at the LLL and newer blocks that were 

delivered to the LLL about two months prior to the tests. 

All blocks were obtained from the same vendor and the 

wood was milled from two days to one month before 

shipment to the NIOSH. 
 

 

 

 

 

 

 

5 

Ten crib blocks (five newer and five older blocks) 

were randomly collected and samples of wood were sent to 

a testing laboratory for moisture, ultimate analysis and 

heating value determinations. Each crib block set was 

constructed on foundation consisting of 8 solid concrete 

blocks. A total of 34 crib blocks were stacked vertically to 

build each crib set (17 of the older blocks and 17 of the 

newer blocks). Each row of blocks was oriented 

perpendicular to the adjacent row. The bottom row 

contained four blocks (two newer blocks on the outside 

and two older blocks on the inside), the next row contained 

four blocks (two newer blocks on the inside and two older 

blocks on the outside). The next row contained three 

blocks (two older blocks on the outside and one newer 

block on the inside). The next row contained three blocks 

(two newer blocks on the outside and one older block on 

the inside). The remaining rows contained two blocks each 

alternating between the new and older blocks in a row. 

The blocks were secured to the roof with wedges as 

needed. In order to insure the maximum stability of each 

crib set, for the longest period of time, each crib set was 

wrapped with poultry fencing that was affixed to the wood 

with staples. 

Crib Block Fire Tests 

The crib fire tests were designed so that four sets of crib 

blocks would be burning simultaneously as the combustion 

products were measured. The estimated heat release rate of 

the fire or estimated energy output of the fire was 

calculated from the gas data and the intensity of the fire 

(and smoke rollback) was monitored remotely using the 

video camera. The estimated heat release rate was 

determined using the amount of CO and CO2 in the 

combustion product air stream and the rate of consumed 

oxygen. The methodology used for making the estimated 

heat release rate calculations is defined in detail in by 

Smith et al. (1995). The heat release rate estimations were 

made using the data collected by the MSHA infrared and 

electrochemical equipment at gas sample arrays 1 and 2 

(CO, CO2 and O2) and the NIOSH thermocouple data 

collected at the same locations. 

In this study, a total of five tests were conducted 

including two crib fire control tests. The first control test 

involved crib block sets that were stacked in a normal 

manner and the second control test involved crib block sets 

that were normally stacked and enclosed in a steel 

framework. The framework was designed to make the crib 

block sets stand upright for a maximum period of time. 

The control tests were designed to serve as the base case 

for the extinguishment tests and the fires were permitted to 

burn until the estimated heat release rate declined 

significantly. Three crib set fire tests with extinguishing 

agents (fire extinguishers, water and gas-enhanced foam) 

were also conducted. These fires were permitted to burn 

until they were emitting a stable and steady amount of heat 

(as determined by the heat release rate calculations), at a 

consistent level of intensity with minimal smoke rollback 

(as determined by the video camera) before the fire 

extinguishing agents were applied. If a crib block set fell 

prior to application of the fire suppression material, an 

interval of time was needed to allow the fire to stabilize 

before the fire suppression material was applied. In this 

manner, the effect of applying the extinguishing agents to 

the fire could be readily observed in the heat release rate 

data would not be perturbed by dramatic variations caused 

by changes in the geometry of the blocks or intensity of the 

fire. A brief summary of each test follows. 

5.1 Test Nos. 1 and 2 (Control Tests) 

During test No. 1, after the gas supply was turned off, it 

was observed that the back set of blocks were burning 

more intensely than the front set of blocks most likely 

because they were sheltered from the ventilation air flow 

by the front set of crib blocks. Although the fire grew 

vertically through each crib block set, the ventilation air 

currents caused the fire to burn more intensely towards the 

back side (downwind side) of each crib block set 

(figure 2). It was determined that this burning condition 

would most likely cause the crib sets to topple over rather 

than collapse vertically. The fire burned unremarkably 

until 94 minutes into the test when the rear left crib block 

set fell down. About 18 minutes later (112 minutes into the 

test) the rear right crib block set fell down. About 30 

minutes later (142 minutes into the test) the front left crib 

block set fell down into the debris of the left rear crib block 

set and about 20 minutes later (162 minutes into the test) 

the front right crib block set fell down into the debris of the 

rear right crib block set. Each time a crib block set fell, the 

intensity of the fire increased for a short period of time. 

Figure 2. Control test - Burning crib block sets 

As discussed earlier, test No. 2 was designed to serve 

as the alternate control base case for the tests and involved 

four crib block sets that were enclosed in a steel 

framework. A plot of the estimated heat release rate and 

the products of combustion for both control tests are shown 

in figure Nos. 3A-C. From the figures, it appears that test 

No. 1 emitted a larger amount of heat and produced a 
 

Figure 3A. Plot of estimated heat release rate and products 

of combustion for crib block tests Nos. 1 and 2. 

 

 

larger amount of CO2 and less CO suggesting more 

complete combustion of the crib blocks than in test No. 2. 

Also, the gas chromatograph data (figure 3C) shows that 

H2, C2H2, C2H4 and C2H6 gases was observed in the 

combustion product air stream during both tests and these 

gases are most likely the products of incomplete 

combustion and pyrolysis of the wood. During test No. 1, 

the concentration of hydrogen and the hydrocarbon gases 

appeared to follow the general trend of the CO gas 

concentration. This same relationship was observed in the 

H2, C2H2, C2H4 and C2H6 gas concentrations measured 

during test No. 2. 

Each time a crib block set fell, the geometry of the 

wood changed and the fire burned more intensely for a 

period of time. The change in the intensity of the fire is 

reflected as an increase in the estimated heat release rate 

immediately following one of these events along with the 

associated increase in the products of combustion. The 

increase in fire intensity is most likely due to the close 

Figure 3B. Gas chromatograph data for test No. 1. 

Figure 3C. Gas chromatograph data for test No. 2. 
 

 

 

 

 

 

 

 

 

Figure 4. Use of fire hose during crib block fire test No. 3. 

 

 

 

 

 

 

 

proximity of the fallen burning crib blocks and the 

associated heat build-up. As planned during test No. 2, the 

steel framework did indeed hold the crib sets upright 

longer than the unconfined crib block sets in test No. 1. It 

was decided that framework system, though useful for 

keeping the crib sets erect, did not substantially extend the 

life of the fire tests and represented a considerable 

deviation from typical crib block configuration used in a 

coal mine setting. The steel framework system was 

therefore not used in any of the subsequent extinguishment 

tests. 

5.2 Test No. 3 (water suppression agent) 

This test was designed to observe the effects of water 

application on a deep-seated crib set fire because water is 

the most commonly available fire suppression technology. 

Water is an effective suppression and extinguishing agent 

because it cools the wood surfaces and therefore reduces 

rate of pyrolysis. For this test, water was supplied from a 

fire truck to a fire hose that was equipped with an 

industrial plastic fog nozzle (the type that is typically 

available in a coal mine) that was adjusted to form stream 

flow. A total of 9,100 liters (2,400 gallons) of water was 

available from the truck for the test. Water was supplied 

through the fire hose to the nozzle at a rate of 284 l/min 

(75 gal/min) at 690 Kpascal (100 psi). The test was 

initiated in the same manner as the control tests. It was 

decided to apply the water extinguishing agent at about 

76 minutes into the test because the fire had reached a 

steady-state burning rate. 

The individuals selected to apply the water to the fire 

were NIOSH technicians who had previously served as 

coal miners and had training and experience in the use of a 

fire hose. The technicians were instructed to apply the 

water until they observed that the fire had been 

extinguished. For personal safety reasons, the technicians 

were also instructed not to progress past a line that had 

been drawn on the entry floor (perpendicular to the trend of 

the entry) about 18 in upwind from the leading edge of the 

crib block sets. This location was selected because it would 

keep the technicians out of the smoke and away from the 

heat of the fire. Water was applied to the fire for about 4 

minutes when the technicians decided the fire had been 

extinguished and a total of 300 gallons of water was used 

(figure 4). Observations of the wood showed that the 

horizontal surfaces appeared to be wet and water was 

observed to be actively dripping from the vertical surfaces. 

About 4 minutes after the water application was 

completed, hot spots (glowing embers) were observed in 

the rear left and rear right crib block sets. At about 52 

minutes after the water application was stopped, small 

flames were observed in the rear left crib block set. The 

embers and flames eventually self-extinguished and no 

other events were observed. 

5.3 Test No. 4 (gas-enhanced foam suppression agent ) 

This test was designed to observe the effects of a portable 

gas-enhanced foam fire suppression technology. 

Compressed air or nitrogen gas, when added to a mixture 

of foam concentrate and water, creates foam that can 

expand up to twenty times the original liquid volume. 

Foam addresses a fire condition through evaporation of 

contained water and through cooling by energy removal. 

The system used was a Sentinel 120RS unit supplied by 

USF Equipment and Services (a research partner in this 

test). The Sentinel 120RS is a self-contained fire fighting 

system that uses the patented Hellfighter® mixing chamber 

to create foam (USF, 2006). The system used was capable 

of producing 9,100 liters (2,400 gallons) of gas enhanced 

foam using a mixture of water, a small amount of Mine 

Fire Fighting Foam® (MFFF) concentrate and nitrogen 

gas. The system can discharge up to 1135 l/min 

(300 g/min) of gas-enhanced foam. Prior to the entry into 

the FSF, the NIOSH technicians were instructed on the 

proper use of the Sentinel unit and application of the foam 

product on the fire. As in the previous test, the technicians 

were instructed to apply the gas-enhanced foam until they 

observed that the fire had been extinguished. 

The test was initiated in the same manner as the 

previous tests. Gas-enhanced foam application began 

103 minutes into the test when the estimated heat release 

rate of the fire had generally stabilized (figure 5). About 

1 minute later, the right rear crib block set fell down. 

Foam application continued for about 8 minutes when the 

technicians decided that the fire had been extinguished. A 

total of 9,100 liters (2,400 gallons) of gas-enhanced foam 

(the entire capacity of the system) was used. At about 

40 minutes after the foam application had been completed, 

the foam had degraded to the point were it was no longer 

observed on the vertical surfaces and 120 minutes after the 

foam application was completed the foam was no longer 

observed on the horizontal surfaces (on the crib blocks or 

the simulated mine floor). From a fire perspective, at about 

63 minutes after the foam application was completed, a 

small flame was observed in the lower portion of the front 

right crib block set and this flame continued to burn until 

the completion of monitoring for this test. A close 

inspection of this crib block set area indicated that it was 

sheltered from foam application and the flame was most 

likely a result of a glowing ember. 
Figure 5. Use of gas-enhanced foam during crib block fire 

test No. 4. 

 

 

 

 

5.4 Test No. 5 (fire extinguisher agent) 

This test was designed to observe the effects of using fire 

extinguishers on a deep-seated crib block fire. Fire 

extinguishers are rated according to the extinguishing 

agent's effectiveness in controlling one or more classes of 

fire. An ABC-rated fire extinguisher is capable of 

addressing A, B and C class fires (combustible solid 

materials, flammable liquids, and energized electrical 

equipment) and is commonly found in underground coal 

mines. ABC-rated fire extinguishers contain 

monoammonium phosphate and/or ammonium sulphate 

powder that leaves a non-flammable layer of material 

(which melts at a low temperature) and blocks gas and heat 

transfer at the fuel surface. For this test, four, 13.6-kg (30­

lb) fire extinguishers were placed in the FSF upwind of the 

crib block sets. To ensure that the extinguishers were in 

proper working order, they were filled with ABC powder 

and were outfitted with new CO2 cartridges the day before 

the test. 

The fire test was initiated in the same manner as the 

previous tests. Use of the fire extinguishers on the fire 

began at 161 minutes into the test when the estimated heat 

release rate of the fire had generally stabilized (figure 6). 

The extinguishing work continued for about four minutes 

until the all of the available material was applied. A total of 

about 45.4 kg (100 lbs) of ABC powder was used on the 

fire. The powder was observed on the horizontal surface 

and some of the vertical surfaces. At about 15 minutes 

after the application of the extinguishing agent was 

completed, small flames were observed in the debris from 

the left rear crib set and glowing embers were observed in 

the lower area of the front left crib set. The flames and 

embers continued to burn until the end of the test. 

Figure 6. Use of fire extinguishers during crib block fire 

test No. 5. 

6 Discussion 

Wood cribs are used throughout underground coal mines as 

a secondary means of roof support. A mine fire can quickly 

propagate through the timbered passageways 

producing life-threatening hazards such as toxic fumes, 

smoke, and heat (Egan and Litton, 1986). During the crib 

fire tests, significant increases in heat output and CO2 

production were observed whenever a crib block set fell 

and the geometry of the burning wood pile changed or if an 

intense burning event occurred. CO gas production 

followed a gradual build-up in all of the tests and then 

declined as expected in the control tests as the fire reduced 

in size. In all of the tests, significant levels of H2 were 

detected and small concentrations of C2H2, C2H4 and C2H6 

gases were observed in the combustion product air stream 

and were most likely the product of incomplete combustion 

and pyrolysis of the wood. However, because of the variety 

of wood species used in these tests and the fact that the fire 

within each crib set was burning differently at the bottom 

of the set as compared to the top, it is impossible to 

determine exactly where the gases originated. As the crib 

block set fires evolved, the change in gas concentration of 

these gases appeared to follow the same general trend as 

either CO2, CO or both gases together. 

It was observed that the intensity of a crib block set fire 

could grow quickly creating localized intense burning 

event. During these events, there was a sudden 

uncontrolled intense burning of the crib block sets at the 

roof level, followed by fire growth towards the rib areas 

with intense smoke rollback. The intense burning events 

last for only a few minutes and the fire did not readily 

consume the crib blocks. This is most likely because the 

combustion products (due to incomplete combustion and 

pyrolysis of the wood material) migrated upward through 

the blocks and accumulated at the roof level (in the 

relatively calm air spaces) along with heat from the fire. 

The fire then grew quickly upwards through the crib block 

sets and consumed the combustion products near the mine 

roof. Once the combustion products were consumed, the 

intensity of the fire was reduced to about the same level 

observed before the event occurred. 

All of the fire extinguishing agents tested appeared to 

be capable of extinguishing a deep-seated crib block fire. 

Each extinguishing agent performed as expected when 
 

 

 

 

 

7 

applied to a burning surface. The fact that none of the fire 

extinguishing agents completely extinguished any of the 

fires is attributed to the crib block set geometry and the 

procedure used to fight the fires, rather than limitations of 

the fire extinguishing agents. The complicated geometry of 

the lower portion of the crib block sets was needed to 

create the fires; however, this geometry also created small 

inconspicuous open areas. These areas were difficult or 

impossible to access with fire suppression agents given the 

fact that the fires could only be fought from the front and 

to a limited degree from the sides of the crib block sets. 

Furthermore, the poultry fencing used to support the crib 

block sets also prevented the placement of the spray 

nozzles inside the crib block sets thus limiting the 

application of the extinguishing agents. 

When a crib block set fell, the geometry of the crib 

blocks became much more complicated and the NIOSH 

technicians could not directly access and separate the fallen 

crib blocks to apply the extinguishing agents. The need to 

separate the burning blocks is considered to be critically 

important to the process of completely extinguishing a crib 

block set fire. This also emphasizes the need to watch over 

an assumed extinguished crib block fire, as undetected and 

unseen hot spots could reignite the fire. 

Results and Conclusions 

In this study, a series of large-scale, deep-seated wood crib 

fire tests were conducted in partnership with MSHA at the 

NIOSH Fire Suppression Facility to measure the various 

combustion products and to observe the extinguishment 

capability of commonly available fire suppression 

equipment, including dry powder fire extinguishers, water 

and gas-enhanced foam. These tests are part of a largescale, deep-seated fire test program that is ongoing at the 

NIOSH Lake Lynn Laboratory. 

During the crib block set fire tests, combustion gas 

information was collected in an attempt to characterize the 

fires. In all of the tests, H2, C2H2, C2H4, and C2H6 were 

observed in various concentrations in addition to the gases 

that were expected (CO2 and CO) in the combustion gas air 

stream. The gases were most likely the product of 

incomplete combustion and pyrolysis of the wood. The 

presence of H2, C2H2, C2H4, and C2H6 in the crib block fire 

combustion product air stream could offer a viable 

explanation as to why these gases have also been detected 

at some of the mine fire sites. Analysis of gas samples 

collected during the planned deep-seated coal fire tests will 

undoubtedly provide additional insight. 

All of the extinguishing agents applied to the crib block 

fires (water, gas-enhanced foam and ABC powder) appear 

to be capable of extinguishing the fires if they are placed 

on all burning surfaces. During our tests, after the 

extinguishing agents were applied, the severity of the fire 

was significantly reduced to the point where safe 

evacuation from the fire area was possible and additional 

fire-fighting resources could have been accumulated and 

used to watch over the debris from the fire, separate the 

blocks and extinguish any and all remaining “hot spots”. 

Acknowledgements 

The authors would like to recognize Brian Blashich, 

Melanie Calhoun, Mark Schroeder, and Donald Sulkowski, 

MSHA, Alden Ozment, USF Equipment and Services, 

Richard A. Thomas, John Soles and Eric S. Weiss, NIOSH 

and the NIOSH staff at the LLL, for their professionalism, 

dedication, and assistance in the conduct of the field work 

needed to complete this study. We would also like to 

recognize Thomas A. Gray, GAI Consultants, Inc., Mark 

Schroeder, MSHA and Dr. Liming Yuan, NIOSH for their 

expertise in providing the technical review of this paper. 

Disclaimer: The findings and conclusions in this report 

are those of the authors and do not necessarily represent 

the views of the National Institute for Occupational Safety 

and Health. 

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