The Status of Mine Fire Research in the United States 

M. A. Trevits, L. Yuan, A. C Smith, E. D. Thimons, G. V. Goodman 

National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, 

Pittsburgh, PA 

ABSTRACT: During the time period from 1990-2007, 1601 reportable fires occurred in the U.S. 

mining industry (an average of 89 fires per year). The leading causes of U.S. mine fires were flame 

cutting and welding operations, frictional heating and ignitions, electrical shorts, mobile equipment malfunctions, and spontaneous combustion. The fact that mine fires continue to occur with an 

alarming regularity reinforces the importance of recognizing and eliminating the potential hazards 

and the overall need for improved fire control and suppression technology to ensure the best possible 

outcome during a mine fire. The National Institute for Occupational Safety and Health (NIOSH) is 

conducting an evolving comprehensive program of research that is addressing mine fire prevention, 

detection, management and suppression. This paper presents a summary of recent research accomplishments and provides an overview of the next phase of the NIOSH mine fire research program. 

1. INTRODUCTION 

The U.S. mining sector employs approximately 331,000 people and has one of the highest fatality 

rates of any U.S. industry. Fatalities, injuries, and disasters, although less frequent than in the past, 

continue to occur with alarming regularity (NRC, 2007). From 1990-2007, 1601 reportable fires (an 

average of 89 fires per year) occurred in the U.S. mining industry (figure 1). The leading causes of 

U.S. mine fires include flame cutting and welding operations, frictional heating and ignitions, electrical shorts, mobile equipment malfunctions, and spontaneous combustion (NIOSH, 2008a). 

The overarching goal of the NIOSH fire research program is to reduce the risk of mine fires 

through the development of new or improved strategies and technologies for mine fire prevention, 

detection, control and suppression. To accomplish this goal, NIOSH is conducting research aimed at 

ensuring that fire-safe materials are used, that combustibles are properly handled and stored, that mechanical and electrical equipment is properly used and maintained, and that personnel are adequately 

trained and educated in fire safety practices. NIOSH research is developing rapid and reliable fire 

sensing systems, guidelines for selecting and using these systems, investigating the principles of fire 

dynamics and the interaction of gaseous or chemical agents with an expanding flame. In addition, 

research is addressing the role that ventilation plays in fire control and extinguishment, and how different fire and smoke mechanisms can impact these interrelationships (NIOSH, 2008b). 
Figure 1. Reported fires for the U.S. mining industry from 1990 to 2007 (DeRosa, 2008). 

2. NIOSH MINE FIRE RESEARCH 

Current NIOSH research is focused on understanding and controlling spontaneous combustion, 

the causes of flame cutting and welding fires and injuries, the effects of ventilation on conveyor belt 

fire suppression systems and remote methods for addressing coal mine fires. The goal of this work is 

to reduce the number of fires and to improve mine fire control and suppression technology to ensure 

the best possible outcome during a mine fire. A report on the status of each program area follows. 

Spontaneous Combustion – Spontaneous combustion continues to be a hazard for U.S. underground coal mines, particularly in western U.S. where the coal is generally of lower rank. For the 

period 1990 – 2006, more than 20 underground spontaneous combustion fires occurred. Spontaneous combustion occurs when the heat that is produced by the low temperature reaction of coal with 

atmospheric oxygen is not adequately dissipated through conduction and/or convection, resulting in 

a net temperature increase in the coal mass. Coal oxidation is an irreversible exothermic reaction and 

its reaction rate increases with temperature. The increase in temperature leads to higher oxidation 

rate. If not averted with an appropriate action, this process results in the thermal runaway and a fire 

ensues. The spontaneous heating of coal often occurs in a gob area and may not be easily detected. 

The risk of an explosion ignited by a spontaneous combustion fire is also present in those mines with 

appreciable levels of accumulated methane gas. In fact, three of the mine fires mentioned above also 

resulted in subsequent methane gas explosions. The incidence of such fires and the associated explosion hazard is expected to increase with the projected increased mining of lower rank coals, deeper 

mines with more methane gas, and the growth in the size of longwall panels. 

A computer model has been developed from existing computational fluid dynamic (commonly 

called “CFD”) codes to describe the ventilation pathways through the immediate gob. Simulations 
have been conducted for a variety of bleederless and bleeder ventilation scenarios to evaluate the 

effect of methane emission rate and ventilation on self-heating in longwall gob areas. This work can 

be used to assist in the design of ventilation systems where spontaneous combustion risk is high. 

Flame Cutting and Welding – To determine the causes of the fires and injuries caused by flame 

cutting or welding operations, accident investigation reports were scrutinized, workers were interviewed, and flame cutting and welding operations at several underground coal mines were observed. 

The data from these investigations was analyzed to determine the root cause of flame cutting and 

welding fires in the coal mining sector. Promising direct interventions to prevent the root causes of 

flame cutting and welding fires were identified and evaluated in field tests at operating underground 

coal mines. Existing training methods and procedures were examined and improvements to these 

methods and procedures were developed and tested in the field. A safety awareness training toolbox, 

“Tame the Flame,” is planned for release in the near future. 

Conveyor Belt Fire Suppression – NIOSH, in partnership with the Mine Safety and Health Administration (MSHA), initiated a test program to determine the effectiveness of fire suppression systems on conveyor belt fires in entries with high-velocity air flow (figure 2). Full-scale experiments 

evaluated the effectiveness of dry powder chemical suppression systems, water sprinkler systems, 

and water deluge systems in conveyor belt entries at air velocities of 0, 2.5 and 7.1 m/sec (0, 500, 

and 1400 ft/min). The data from this work will be used to develop guidelines for the installation and 

use of fire suppression systems in ventilated belt entries. In late 2007, the scope of this research was 

modified to include the recommendations made by the Technical Study Panel on the utilization of 

belt air and the composition and fire retardant properties of belt materials in underground coal mining (Mutmansky, 2007). 

Figure 2. Conveyor belt fire suppression system set-up at the NIOSH Fire Suppression Facility 

(Rowland, 2008). 
In a related study, conveyor belt, typical of the type used in metal/nonmetal mines, where no 

mandatory fire resistance standards apply, were evaluated for their fire resistance. The results clearly 

showed the hazards of using non-approved conveyor belting and demonstrated that the use of approved conveyor belting can significantly reduce potential fire hazards. 

Remote Methods for Addressing Coal Mine Fires – The ability to remotely address coal 

mine fires can reduce worker exposure to hazardous situations. The objective of this work is to evaluate, improve or modify remote fire-fighting technologies, including remotely installed mine seals 

(ventilation barriers), and fire control and suppression technology. This research effort is being conducted with active industry participation and with the input from MSHA technical specialists serving 

as research partners. Full-scale remote mine seal installation experiments have been conducted to 

evaluate cement-based and rigid-foam based materials at the NIOSH Lake Lynn Experimental Mine 

(LLEM). The LLEM (located approximately 97 km (60 mi) southeast of Pittsburgh, Pennsylvania) 

is a world-class, highly sophisticated underground facility where large-scale explosion trials and 

mine fire research is conducted. This work has resulted in new understandings of the limitations of 

the technology and development of novel downhole tools to facilitate accurate placement of mine 

seal materials. Preliminary research on nitrogen gas-enhanced foam (foam resulting from commingling of nitrogen gas, water and a specialized foam concentrate) shows that foam can be stable in the 

mine opening and can accumulate and flow through mine workings (figure 3). 

Figure 3. Compressed air gas-enhanced foam accumulating behind and moving through crib block sets at the 

LLEM. 

3 FURTURE NIOSH MINE FIRE RESEARCH 

Planned work under the NIOSH mine fire research program will continue the spontaneous combustion modeling effort. The work will focus on western U.S. coal mines by simulating longwall 

gob areas and collaborating with western U.S. coal mine operators to collect spontaneous combustion data to calibrate the CFD model. CFD modeling will also be used to investigate nitrogen gas 

injection strategies to prevent the spontaneous heating in coal mines using bleederless ventilation 

systems and to suppress the spontaneous heating in coal mines using bleeder ventilation systems. It 

is hoped that this work will result in improved understanding of the conditions that lead to heating 
events and should also result in new ventilation practices and technologies to reduce the risk and 

number of fires. 

The conveyor belt fire suppression program will focus on the reduction of the hazards of underground coal mine fires, particularly in conveyor belt entries, by applying recent technological advances in the areas of fire-resistant and fireproof belt materials, belt fire suppression systems, atmospheric monitoring systems, and computer codes for predicting and assessing in real-time the impact 

of fire on the mine ventilation system. In addition, the work will include an overall evaluation of the 

flammability of conveyor belts, modeling of conveyor belts fires, modeling of contaminant spread, 

fire risk assessment, and training and maintenance. It is expected that the research output from this 

work will substantially reduce the number of fires and injuries/fatalities due to conveyor belt fires 

and will significantly improve the level of fire safety in mines. 

Remote mine fire suppression research will continue and will involve the testing of injected inert 

gas and gas-enhanced foam to extinguish large-scale, deep-seated coal and coal-wood crib fires. 

During each fire, fire gases, and heat build-up and release will be continuously monitored as each 

suppression technology is applied to determine fire suppression mechanics and if technology modifications are needed. Included in the work plan is a test of jet engine exhaust technology for mine 

fire suppression. A controlled, large-scale, deep-seated coal fire will be built underground and a jet 

engine will be coupled to the LLEM mine ventilation system via the fan shaft or a drift opening so 

that the jet engine exhaust gases pass over the fire. The complete suite of jet engine exhaust gases 

will be monitored along with fire heat build-up and release. In addition, heat build-up and moisture 

loss will be monitored in the rock mass (or via instrumented samples placed near the jet engine exhaust) to determine the effects of heat on mine void and rock mass degradation. Finally, inflatable 

temporary ventilation control devices will be evaluated through deployment, multi-day inflation and 

air leakage tests at the LLEM to define the capability and limitations of these devices in a simulated 

coal mine setting (figure 4). It is thought that these devices could be used by the U.S. coal mining 

industry to temporarily close an underground mine area in response to a fire or spontaneous combustion heating event and to temporarily redirect mine ventilation during longwall equipment moves or 

during stopping construction. 

Figure 4. Testing of an inflatable temporary ventilation control device. 
4. SUMMARY 

Mine fires represent one of the greatest threats to those working in the underground mine environment. NIOSH mine fire research is addressing a wide spectrum of problem areas facing the U.S. 

mining industry. The intent of the research is to provide the mine operator and miners with an understanding of the conditions that could lead to a fire, the capability to detect unusual heating or fire 

conditions, and the technology to suppress and extinguish a fire to ensure the best outcome possible. 

Research papers that discuss much of the work presented in this article are available through the 

NIOSH mining website. A discussion and description of the NIOSH Mining Research Program and 

copies of all NIOSH published mining research work can be obtained by browsing to http://www. 

cdc.gov/niosh/mining. 

REFERENCES 

[1] DeRosa, M. I., 2008, Industrial Hygienist, Pittsburgh Research Laboratory, NIOSH, Personal Communication, March 22. 

[2] Mutmansky, J. M., Brune, J. F., Calizaya, F., Mucho, T.P., Tien, J.C., Weeks, J.L., 2007, Final Report of 

the Technical Study Panel on the Utilization of Belt Air and the Composition and Fire Retardant Properties of Belt Materials in Underground Coal Mining, NIOSH, 132 p. 

[3] National Institute for Occupational Safety and Health, 2008a. NIOSH Mining Webpage, <http://www.cdc. 

gov/niosh/mining/topics/topicpage19.htm>, April 8. 

[4] National Institute for Occupational Safety and Health, 2008b. NIOSH Mining Webpage, 

<http://www.cdc.gov/niosh/mining/aboutus/programarea13.htm>, July 5.
 

[5] National Research Council and Institute of Medicine (NRC). 2007. Mining Safety and Health Research 

at NIOSH. Committee to Review the NIOSH Mining Safety and Health Research Program. Rpt. No. 2, 

Reviews of Research Programs of the National Institute for Occupational Safety and Health. Washington, 

D.C.: The National Academies Press, 290 p. 

[6] Rowland, J. H., 2008, Research Physicist, Pittsburgh Research Laboratory, NIOSH, Personal Communication, April 22.