Reducing the fire and explosion 

hazards of flame-cutting and welding in 

underground coal mines
�

W. D. MONAGHAN 

W. D. Monaghan, member SME, is general engineer with the 

National Institute for Occupational Safety and Health, Pittsburgh, 

PA 

Abstract 

 One of the major ignition sources of fires and explosions in underground U.S. coal mines is flame cutting and welding. 

On May 20, 2006, a flame-cutting operation at the Darby Mine No. 1 led to an explosion that resulted in five fatalities. On 

Jan. 22, 2003, another explosion caused by flame cutting at the McElroy Mine resulted in three fatalities and three serious injuries. On June 22, 1999, a flame-cutting and welding operation at the Loveridge Mine caused a fire that required 

sealing the mine for an extended period. On March 19, 1992, an explosion initiated by welding at the Blacksville No. 1 

Mine resulted in four fatalities. These examples of mine incidents demonstrate the need to conduct research to develop 

best practices for safely conducting flame cutting and welding in underground coal mines. 

 The National Institute for Occupational Safety and Health (NIOSH) conducted a study on fires and explosions in 

underground U.S. coal mines that were caused by flame-cutting and welding operations to determine the root causes of 

these types of incidents. The methodology included interviewing mining personnel who perform flame-cutting or welding 

operations in underground U.S. coal mines and visiting mines to observe these operations. In addition, MSHA reports of 

investigations and accidents statistics were analyzed. The findings were used to identify and compare differences between 

flame-cutting and welding practices and techniques in small and large mines, eastern and western mines, low-seam and 

high-seam mines, room-and-pillar and longwall mines, and between experienced miners and new miners. As a result of 

this study, best practices were developed to reduce the number of fires and explosions caused by flame cutting and welding. This paper provides a summary of this research. 

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. 

Introduction 

Flame-cutting and welding activities 

in underground U.S. coal mines continue to be a major originator of fires and 

explosions. Seventeen reported fires 

or explosions in underground U.S. coal 

mines for the period 1990 - 1999 were 

initiated by flame-cutting and welding 

activities (DeRosa, 2004). In addition, from 2000 - 2007 six underground 

fires or explosions were reported that were attributed to 

flame-cutting and welding operations and caused injuries 

or fatalities (DeRosa, 2008). These fires occurred when 

hot sparks or hot molten metal came in contact with combustible materials, such as coal, oil, grease, clothing, rags, 

paper and aerosol cans. These explosions occurred when 

hot sparks or hot molten metal came in contact with flammable gases. The source of fuel for the majority of these 

incidents was methane gas. The Mine Safety and Health 

Administration’s policy in 30 CFR §75.1106 states that 

methane tests must be done continuously in all locations 

where methane is likely to exist (MSHA, 2007). 

In order to reduce the fire and explosion hazards 

caused by flame-cutting and welding operations in underground coal mines, a study to better understand the 

root causes of incidents and recommended best practices was completed by the National Institute for Occupational Safety and Health. The 

information from this study is presented here in the following format. 

In the first section of this paper, case 

histories are presented of major fires 

and explosions in underground U.S. 

coal mines that were caused by flamecutting or welding operations. The 

second section of the paper identifies 

and discusses the root causes of fire 

or explosions associated with flame cutting or welding 

operations. Results of flame-cutting experiments performed at NIOSH’s Lake Lynn Laboratory are presented 

in the third section of this paper. The paper concludes 

with recommended best practices and the conclusions of 

this research. 

Darby Mine explosion 

On May 20, 2006, an explosion occurred in a sealed 

section of the Darby Mine No. 1 in Kentucky, resulting in 

fatal injuries to five miners and injuries to one miner. A 

methane explosion occurred behind a block seal. MSHA 

determined that the explosion was caused by sparks that 

were generated by flame-cutting of a metal roof strap that 

passed above the seal (MSHA, 2006). Figure 1 shows the 

type of metal roof strap that was being flame-cut by an 

oxygen and acetylene torch at the time of the explosion. 
FIGURE 1 

Metal roof strap. 

Figure 2 shows the actual debris from a stopping, which 

was destroyed by the explosion.

FIGURE 2 

Debris from a stopping near the explosion in Darby 

Mine No. 1 (MSHA, 2006). 

MSHA further determined that the incident occurred because the operator 

did not observe basic mine safety practices and critical 

safety standards were violated. Mine management failed 

to ensure that proper seal construction procedures were 

utilized in building seals, that safe work procedures were 

used while employees attempted to make corrections 

to an improperly constructed seal and that miners were 

adequately trained (MSHA, 2006). 

McElroy Mine explosion 

On Jan. 22, 2003, an explosion occurred inside an airshaft under construction for the McElroy Mine in West 

Virginia. Six miners were inside the shaft at the time of 

the explosion. The explosion fatally injured three miners 

and seriously injured three others. The miners were attempting to remove corrugated galvanized steel sheeting 

that blocked access to the unventilated water ring being 

constructed. Figure 3 shows the corrugated, galvanized 

steel sheeting after the explosion had occurred. 

FIGURE 3 

Corrugated, galvanized steel sheeting after the 

explosion in McElroy Mine (MSHA 2003). 

After 

obtaining a reading of 0.2% methane on a handheld detector, the foreman directed the mechanic to cut the panning with an oxygen and acetylene torch. The mechanic 

ignited the torch and started to flame cut the panning. An 

explosion occurred when the torch cutting process ignited an explosive methane-air mixture contained inside the 

water ring. MSHA determined that the incident occurred 

because the examination for methane was not adequate. 

An adequate examination would have required testing 

for methane in all areas that could have been affected by 

the use of the cutting torch (MSHA, 2003). 

Loveridge Mine fire 

On June 22, 1999, a mine fire was discovered in an 

approach to a worked-out area in a former belt conveyor entry in the Loveridge Mine in West Virginia. While 

checking the work site where a flame-cutting operation 

was completed at 2:00 p.m. on June 21, 1999, a foreman 

discovered the fire at approximately 12:50 a.m. on June 

22, 1999. He observed an orange glow near a permanent stopping inby the location where the cutting operation had been performed. An attempt was made by 

mine personnel to extinguish the fire; however, the fire 

was so intense the mine was evacuated and sealed the 

next day. Four days after the mine was sealed, an explosion occurred that caused major damage to ventilation 

structures and mining equipment. Recovery of the mine 

started in July 2000, and required approximately one year 

to complete. 

MSHA’s investigation concluded that heated metal 

from the flame-cutting operation was the ignition source. 

Flame-cutting had been completed approximately 11 

hours prior to the discovery of the fire. A heated metal spark from the cutting operation passed through an 

opening in the adjacent stopping, and coal and other 

combustible material within the worked-out area were 

most likely ignited. The root cause of this fire was that 
a diligent search for fire in all potentially affected areas 

was not made during and after the cutting operations 

(MSHA, 1999). 

Blacksville No. 1 Mine explosion 

On March 13, 1992, a cap was placed on a production shaft at the Blacksville No. 1 Mine in West Virginia, 

reducing the amount of intake air entering the shaft. On 

March 17, 1992, actions taken during installation of the 

casing caused further reductions in the amount of air 

entering the shaft. As a result from this reduced ventilation, methane within the explosive range (5%-15%) 

accumulated under the cap. On March 19, 1999, welding 

activities caused a methane explosion resulting in four 

fatalities and three injuries. MSHA’s investigation determined that methane was ignited directly beneath the cap 

by sparks or an electric arc produced by the arc-welding 

operation that was in progress on top of the production 

shaft cap. The root cause of the fire was inadequate examination for methane (MSHA, 1992). 

Root causes of flame-cutting and welding fires and explosions 

To reduce or prevent fires and explosions from occurring, one must understand the nature of their initiation 

and identify the root causes. In this study, the root causes 

of mine fires and explosions caused by flame-cutting and 

welding operations in underground U.S. coal mines were 

identified. MSHA Reports of Investigations (2006; 2003; 

1999; 1992), MSHA Mine Accident Injury-Illness Reports and the MSHA Mining Industry Accident, Injuries 

Employment, Production Data Base (2008) from 1995 

to 2007 were reviewed and analyzed. Ten working coal 

mines were visited to observe flame-cutting and welding 

operations, and interviews were conducted with approximately 100 mine workers who were involved in welding 

tasks. In addition, flame-cutting experiments were conducted at NIOSH’s Lake Lynn Laboratory. The following root causes of fires or explosions from flame-cutting 

and welding operations in underground U.S. coal mines 

were identified: 

1.	� Inadequate or improper methane examination 

and testing (30 CFR §75.1106). 

2.	� Lack of a diligent search for fire during and after 

flame cutting or welding (30 CFR §75.1106). 

3.	� Inadequate inspection of tools and equipment 

prior to cutting or welding (30 CFR §75.1106-5). 

4.	� Improper procedures in preparing surfaces for 

cutting and welding, including degreasing and 

general cleaning (30 CFR §75.1106-4). 

5.	� Inadequate ventilation of the work site (30 CFR 

§75 100). 

6.	� Inadequate training of persons conducting the 

cutting and welding (30 CFR §75.1106-4). 

Flame-cutting experiments 

In order to gain a better understanding of the temperature histories of hot sparks, hot metal strips and hot 

molten metal, three sets of experiments were performed 

at NIOSH’s Lake Lynn Laboratory. In each of these 

experiments the following parameters were utilized. An 

oxygen and acetylene torch was used to flame-cut a metal 

roof strap. An infrared (IR) camera with the appropriate 

instrumentation was used to obtain temperature histories 

of hot sparks and hot metal strips. In addition, a 6.35-

mm (0.25-in.) thick metal strap, which was thicker than 

a metal roof strap, was flame-cut. The cuttings and hot 

molten metal from the cut dropped into a pan filled with 

float coal dust and grease to observe the effects of the hot 

molten metal on the float coal dust and grease. Float coal 

dust is defined as dust that passes a 75-μm (200-mesh) 

sieve. Float coal dust is easily transported by the mine 

ventilation system, can form an explosible coal cloud, and 

buildup on the floors, walls and roof. 

FIGURE 4 

Setup of block and metal roof strap experiment. 

FIGURE 5 

Close-up of the two channels on the metal roof strap. 

Temperature histories of the hot sparks 

experiment 

To conduct the experiment, a mine seal block was 

placed on top of the metal roof strap and the IR camera was positioned on the opposite side of the mine seal 

block where flame-cutting was performed. Figure 4 
shows this experimental setup. The metal roof strap was 

cut from underneath and hot particles traveled through 

the two channels located on the metal roof strap. Figure 

5 shows a close-up of the two channels. Figure 6 shows 

the IR image of several hot sparks and Table 1 lists temperatures of some of the hot sparks identified in Fig. 6. 

Table 1 

Temperatures of hot particles. 

Hot particle Temperature of hot 

identification particle, °C/°F 

1 747/ 1,377 

2 742/ 1,368 

3 760/ 1,400 

4 500/ 932 

5 762/ 1,404 

6 587/ 1,089 

FIGURE 6 

IR image of several hot particles. 

These experimental results showed that flame cutting can 

produce hot sparks with temperatures much greater than 

593° C (1,099° F), the minimum temperature required to 

ignite a methane-air mixture. It should be noted that the 

minimum temperature required to ignite a coal dust layer 

of less than 74 μm (-200 mesh) is 160° C (320° F) (Kuchta, 

1985). Table 2 lists ignition temperatures of eight different coal layer samples. 

Table 2 

Ignition temperature of coal layers (Kuchta, 1985). 

Coal Identification Ignition, °C/°F 

Lignite, California 200/ 392
�

Lignite, North Dakota 180/ 356
�

Bituminous, Fox Hill, CO 180/ 356
�

Bituminous, No. 7 Illinois 160/ 320
�

Bituminous, Whitesburg, KY 190/ 374
�

Bituminous, Bruceton, PA 170/ 338
�

Bituminous, Pocahontas No. 3, 220/ 428
�

West Virginia
�

Bituminous, Laramie No. 3, 180/ 356
�

Wyoming
�

Hot metal strip experiment 

In this experiment, metal strips ranging from 1.27 to 

3.75 cm (0.5 to 1.5 in.) were flame-cut from the metal 

roof strap shown in Fig. 7. 

FIGURE 7 

Metal roof strap prior to flame cutting individual strips. 

The temperature histories 

of the hot metal strips were obtained by recording the 

temperature every 250 milliseconds using the IR camera. 

Figure 8 shows an example of the temperature histories 

of a 1.27-cm (0.5-in.) and a 3.75-cm (1.5-in.) metal strip 

following the cut. 

FIGURE 8 

Temperature histories of two hot metal strips following 

cutting. 

The 3.75-cm (1.5-in.) strip’s temperature remained above 593o C (1,099° F) for 19 seconds, 

and the 1.27-cm (0.5-in.) strip’s temperature remained 
about 593o C (1,099° F) for 10.5 seconds.The results from 

this experiment showed that these hot metal strips were 

capable of igniting a methane-air mixture. 

Hot molten metal experiment 

In this experiment, the effect of hot molten metal on 

float coal dust and grease was observed. Flame-cutting 

was performed approximately 1 m (3.3 ft) above the float 

coal dust and grease. The hot molten metal was allowed 

to fall directly on the float coal dust and grease.The temperatures of the metal, float coal dust and grease were 

recorded using the IR camera, shown in Fig. 9. 

FIGURE 9 

Setup for hot molten metal experiment. 

The hot 

molten metal immediately ignited the grease. After several minutes, flames from the grease appeared to have 

self-extinguished. However, hot spots in the float coal 

dust were observed with a temperature range between 

93-145o C (199-293° F). 

These hot spots were not visible with the human eye 

and were only identified by using the IR camera. The IR 

camera was used to monitor the hot spots for approximately two hours. After two hours, a small fan was placed 

near these hot spots and air at a velocity of 2.03 m/s (6.66 

ft/s) was passed over the hot spots. This air velocity was 

chosen since the air velocity in the belt entry must be at 

least 0.51 m/s (1.67 ft/s) and must not exceed 4.57 m/s 

(15 ft/s) when used to ventilate a working section (CFR). 

This ventilation caused the temperature of the hot spots 

to increase, resulting in re-ignition of the float coal dust 

and grease. The results from this experiment showed that 

hot spots can remain for several hours when not properly 

extinguished and can reignite if sufficient ventilation is 

provided (Hoffman, 1991). 

Best practices to reduce fire and explosion

hazards of flame-cutting/welding 

The Code of Federal Regulations, 30 CFR §75.1106 

requires the following: “All welding, cutting or soldering 

with arc or flame in all underground areas of a coal mine 

shall, whenever practicable, be conducted in fireproof 

enclosures.Welding, cutting or soldering with arc or flame 

in other then a fireproof enclosure shall be done under 

the supervision of a qualified person who shall make a 

diligent search for fire during and after such operations 

and shall, immediately before and during such operations, 

continuously test for methane with means approved by 

the secretary for detecting methane. Welding, cutting or 

soldering shall not be conducted in air that contains 1.0 

volume per centum or more of methane.” Rock dust (109 

kg (240 lbs) minimum) or suitable fire extinguisher shall 

be immediately available during such welding, cutting or 

soldering, (30 CFR §75.1100-2(a)). 

In addition to the CFR requirements, the following 

best practices are provided to reduce the fire and explosion hazards of flame-cutting and welding operations in 

underground coal mines. These best practices are based 

on the root cause analysis of fires and explosions caused 

by flame-cutting and welding operations in underground 

U.S. coal mines, observation of flame-cutting at operating coal mines, interviews with mine workers and flamecutting experiments at NIOSH’s Lake Lynn Laboratory 

and the MSHA report titled “Safety practices for welding 

and cutting operations” (Hoffman, 1981). 

•	� Persons (mine workers and contractors) who are 

required to conduct methane examination during flame-cutting and welding operation should 

have training semi-annually. This training should 

include checks to ensure the methane detector 

device is properly calibrated by inspecting the 

date on calibration sticker and the proper use of 

methane monitors, with and without probes. 

•	� Check for methane thoroughly and continuously 

during the flame-cutting and welding operations, 

and use a methane probe for hard to reach areas. 

Methane gas is colorless, odorless, tasteless, nontoxic, highly flammable and is lighter than air, so 

it can accumulate in areas such as roof cavities, 

get trapped underneath pan lines and other mining equipment. Ventilation should be adequate 

to provide dilution of any harmful gases or toxic 

vapors that may accumulate. 

•	� Persons (mine workers and contractors) whose 

duties include flame-cutting and welding operations should have training semi-annually on the 

Code of Federal Regulations and State Regulations that apply to flame-cutting and welding. 

•	� Use cold-cutting alternatives versus an oxygen 

and acetylene torch for cutting metals, when 

available. Several mines that were visited are 

using hydraulic cutters and punches. However, 

nonflame alternatives have limited application 

and cannot totally replace the use of flame cutting 

in underground coal mines. 

•	� Have a helper observe the flame cutting and 

welding operations. This helper can continuously 

check for methane, immediately extinguish a fire 

and go for additional help if needed. 

•	� Perform an equipment safety inspection prior to 

starting a flame-cutting and welding operation. 

When using an oxygen and acetylene torch: 

1.	� Blow out the cylinder valves before attaching 

regulators. 

2.	� Keep all grease (fingers, gloves) away from oxygen connections. 

3.	� Never force connections. 

4.	� Use the properly sized, clean cutting tips for the 
operation. 

5.	 Check connections for leaks. 

6.	 Replace damaged hoses. 

7.	 Open cylinder valves slowly. 

8.	 Do not use acetylene at pressures higher than 9 

psi. 		

9.	 Never lay acetylene bottles flat. 		They must remain vertical. 		

10. Ensure that flashback arrestors are installed. 

11. Purge the oxygen and acetylene lines before 

lighting the torch. 

12. When lighting the torch,point away from persons 

and combustibles. 

13. Light the acetylene before opening the oxygen 

valve and do not re-light the torch on hot metal 

with the oxygen turned on. 

•	 Have a fire hose hooked up and charged at the 

cutting/welding site.Thoroughly water down the 

surrounding area where all hot sparks and hot 

molten metal can reach prior to a flame-cutting 

and welding operation.		Thisis one of the simplest 

and cheapest interventions to help reduce the 

risk of fire. 		After the flame-cutting and welding 

operation is completed, water down the area 

again. 

•	 Wipe down equipment contaminated with coal 

dust, oil, grease or other combustibles prior to 

flame-cutting and welding operations. 

•	 Apply rock dust to all adjacent areas prior to the 

flame-cutting and welding operation after the 

area has been watered down. 	 	Apply the rock 

dust liberally to cover the entire area where hot 

sparks or hot molten metal may be projected. 

Maintain an adequate supply of rock dust on 

hand to smother any fires that may flame up 

during the operation. 

•	 Maintain accurate records of the flame-cutting 

and welding operations, including the following 

information: 

1.	 Section and exact location(s) where the flamecutting and welding operation was performed. 

2.	 Item or items that were flame cut or welded. 

3.	 The names of mine personnel that performed the 

flame-cutting and welding operation. 

4.	 Time the flame-cutting and welding operation 

started. 

5.	 Time the flame-cutting and welding operation 

was completed. 

6.	 Special precautions should be taken to prevent 

fire or explosion and special instructions should 

be left for the oncoming shift personnel to monitor the site for hot spots. 

•	 Use a thermal imaging camera to check for hot 

spots afterthe flame-cutting or welding activity is 

completed.The approximate cost for an IR camera that could be used for this application ranges 

from $5,000 - $8,000. 		As mentioned earlier, hot 

spots can remain undetected by the human eye 

and are only visible by an IR camera. 

•	 Have the oncoming shift section foreman or a 

competent person inspect the area where flamecutting and welding operations were performed 

and record that the site was re-inspected. 

•	 Discuss flame cutting and welding operations at 

weekly safety meetings. 	 	Discuss any concerns 

related to this type of operation. 

Conclusions

NIOSH conducted a research study on fires and explosions in underground U.S. coal mines caused by flamecutting and welding operations. 		In this study,root causes 

of these types of fires were identified, flame-cutting and 

welding operations were observed and interviews were 

conducted with over 100 underground coal mine personnel whose duties included flame-cutting and welding operations. 		In addition, flame-cutting experiments 

were conducted at NIOSH’s Lake Lynn Laboratory. 		As 

a result of this study, recommended best practices are 

provided for reducing fires and explosions from flamecutting and welding. 

References

CFR, Code of Federal Regulations,Washington, DC: U.S. Government 

Printing Office, Office of the Federal Register. 

DeRosa, M., 2004, “Analysis of mine fires for all U.S. underground and 

surface coal mining categories, 1990-1999,” NIOSH Information 

Circular 9470. 

DeRosa, M., 2008, personal communication. 

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