- - 

The Brookwood Disaster and Electrical Requirements for 


Hazardous (Classified) Locations 


Thomas H. Dubaniewicz, Jr. 


National Institute for Occupational Safety and Health 


PO. Box 18070 


Pittsburgh, PA 15236 USA 


Abstract - Thirteen miners died as a result of 2 explosions in the 

Jim Walter Resources No. 5 mine near Brookwood AL in 

September 2001. Both explosions were ignited in intake air 

entries, and both were probably ignited by electrical equipment. 

With few exceptions, permissible equipment is not required in 

intake air entries of US underground coal mines Researchers 

with the National Institute for Occupational Safety and Health, Pittsbureh Research Laboraton. studied the electrical -. equipmeit ignition sources for the ~ ~ ~ and ~ other w k

disasters to develop recommendations for preventing similar 

disasters Adherence to National Electrical codea requirements 

for flexible cords installed in hazardous (classified) locations 

may have prevented the second massive Brookwood explosion. 

The 30 CFR Part 7 requirements for battery assemblies should 

be reevaluated, taking into consideration United Mine Workers 

of America recommendations and the Zone 1"increased safety" 

standard requirements for battery assemblies, Class 1 Division 

2 or Zone 2 emlosion oroteclion techniaues are recommended 

for intake air equipmedt so that they do not present a methans 

air ienition source under normal oneration. before mine Dower 

is s& do- during emergencies '~atter~'~owered circuits in 

intake air that are likely to remain enerdzed during 

emergencies should be protected by more stringent protection 

techniques, to protect rescudrecovery personnel. 

Index Terms - Class I hazardous location, mine explosion, 

flexible cord, battery assembly, permissible equipment 

I. INTRODUCTION 

Gas or dust explosions are some of the greatest hazards 

faced by underground coal mine workers. Explosions may be 

infrequent, but can account for large numbers of deaths when 

they do occur. Methane gas is released during the mining 

process and accumulates in areas that are not well ventilated. 

Coal dust accumulations can form explosive dust clouds 

when entrained into the air. Methane ignitions or explosives 

can dsperse coal dust layers into the atmosphere that 

subsequently ignite and propagate as powerful explosions. 

Over the last 30 years, a number of fatal underground coal 

mine explosions have been linked to nonpermissible 

electrical equipment ignition sources when flammable gas 

migrated outby the last open crosscut under abnormal 

conditions due to inadequate ventilation (Table 1) [I]. The 

most recent of these fatal intake air explosions occurred at the 

Jim Walter Resources (JWR) Inc. No. 5 mine near 

Brookwood AL in September of 2001, where 13 miners died 

as a result of 2 explosions involving methane and coal dust, 

both of which were ignited in intake air entries, and both of 

which were probably ignited by electrical equipment. 

Researchers with the National Institute for Occupational 

Safety and Health, Pittsburgh Research Laboratory (NIOSH, 

pp~)studied the electrical eauiument ignition sources - for the 

Bro~kwood disaster to . . develop equipment design 

recommendations for preventing similar disasters in the 

future (The and in this report are those 

of the author and do not necessarily represent the views of the 

National Institute ~ ~ d for Occupational Safety and Health.) The

equipment studied was described in the Mine Safety and 

Health Administration [2] and United Mne Workers of 

America 131 . on the disaster. L A 

The term uermissible refers to eauiument . . that meets 

specifications for the construction and maintenance of such 

equipment, to assure that such equipment will not cause a 

Or mine fire (30 CFR 752) I41 

that is methane Or dust 

inby the last open crosscut (30 CFR 75.500), or within 150 

feet of uillar workings or longwall faces 130 CFR 75.1002'1. ,. or in r& entries 730 cF~-75.507), mist be permissible. 

Air quality detectors and measurement devices shall be 

auuroved and maintained in uermissible and urouer ouerating .. . - condition (30 CFR 75.326). Telephones and signaling 

devices shall offer no probable explosion hazard under 

normal oueration if used in -gassv or dustv mine atmosuheres 

(30 CFR 23.6). Electrical components of automatic fire 

sensors must be urovided with urotection against ignition of 

methane or coal'dust (30 CFR' 751103.7)~ The explosion 

protection techniques most familiar to the underground coal 

mining industry are explosion proof enclosures and two-fault 

intrinsic safety. With few exceptions, explosion protected 

electrical equipment is generally not required in intake air 

entries of underground mines. 

I1 THE 2001 BROOKWOOD DISASTER 

On September 23, 2001, two explosions occurred about 1 

hour apart in 4 Section of the JWR No. 5 Mne, resulting in 

13 deaths [2,3]. Prior to the first explosion, four workers 

were building supplemental roof support cribs in an area 

where the mine roof and ribs were deteriorating. A scoop 

battery charging station was under the bad roof, and next to a 

stopping separating methane-laden return air kom kesh 

ventilation air. This mine liberated 17.2 million cubic feet of 

methane per day through the returns and out the mine 

exhausts. Methane bleeders in the roof and floor were 

prevalent. The battery charger was placed next to the 

U.S. Government worknot protected by U.S. copyright 
Table 1. Fatal methane and methane plus coal dust explosions in US underground coal mines since 1976 linked to 

nonpermissible electrical equipment in intake air entries. 

Year Operator, mine, and state Fuel Ignition Possible ignition sources Killed 

location 

1976 Scotia Coal Co., Scotia Methane Intake Normal arcing of battery powered 15 

(1 of 2) Mine, KY locomotive 

1980 Westmoreland Coal Co., Methane Intake Trolley wire powered locomotive 5 

Ferrell #17 Mine, WV 

1983 Clinchfield Coal Co., Methane Intake Battery powered track mounted 7 

McClure #1 Mine, VA mantrip, power center circuit breaker, 

dinner hole light connection, cable 

plug for CM trailing cable, belt 

control cable disconnect or fault, 

ground fault in trailing cable for 

conveyor belt feeder. 

1983 Helen Mining Co., Homer Methane Intake Arcing controller on vehicle 1 

City Mine, PA 

1984 Pennsylvania Mines Corp., Methane Intake Normal arcing of nonpermissible 3 

Greenwich Collieries #1 battery powered locomotive 

Mine, PA 

1987 Double R Coal Co., #1 Methane & Intake Two power centers, battery charging 1 

Mine, VA coal dust cable, faulted permissible scoop. 

2001 Jim Walter Resources Inc., Methane Intake Battery assembly removed from 1 

#5 Mine, Brookwood AL scoop and damaged by roof fall 

2001 Jim Walter Resources Inc., Methane & Intake Damaged block light cable 12 

#5 Mine, Brookwood AL coal dust 

45 

total 

stopping to facilitate battery venting to the return entry. The 

roof caved in before the supplemental roof supports could be 

completed. The cave-in damaged the stopping, allowing 

methane to migrate from the overburden and possibly the 

return entry onto the battery charging station. The cave-in 

also damaged a battery enclosure, shorting the battery and 

igniting the first explosion. Section ventilation controls were 

damaged by the blast. The four miners were injured in the 

relatively minor explosion, three of whom were able to 

escape from 4 Section on a diesel locomotive. The 

incapacitated miner was injured during the first explosion. 

The MSHA report suggests the injuries may have been fatal. 

The 4 Section circuit breaker was tripped to remove power to 

the section; however a block light traffic control circuit 

remained energized because it was powered through a 

breaker located in another mine section. 

Within an hour, 12 miners went towards 4 Section to 

rescue the one remaining incapacitated miner. In the mean 

time, methane gas had accumulated in 4 Section through the 

damaged ventilation controls. Some of the rescuers drove the 

locomotive back into 4 Section. The locomotive ran over and 

entangled slack electrical cable for the live block light traffic 

control system. The cable was damaged in several places, 

exposing energized conductors. Evidence suggests the 

coworkers reached the injured miner and were bringing him 

to safety. It is thought that the rescuers may have disturbed 

the damaged, energized block light cable. Or perhaps one of 

the miners had shown a caplamp onto a photo-switch in the 

master or slave block light units that energized a damaged 

conductor. The spark ignited the second massive explosion, 

killing all the miners. 

III. SELECTED MSHA FINDINGS 

MSHA concluded a live high voltage cable hit by the 

initial roof fall was not a likely ignition source for the first 

explosion. Resistance measurements indicated the cabling 

was robust enough to prevent the conductors from being 

faulted. Even if the cable were faulted, the shielded 

conductors would have caused a ground fault, activating the 

protective circuit breaker in less than a second. The ignition 

did not occur for a few minutes. The robust cabling design 

and the grounded shielding prevented the live high voltage 

cable from being an ignition source. 

MSHA determined a scoop battery was the likely ignition 

source for the first explosion. The roof fall damaged the 

battery assembly such that the steel frame of the battery tray 

contacted both the negative battery terminal and an intercell 

connector. The short circuit produced temperatures capable 
of igniting methane-air mixtures. A permissibility 

examination was completed for the battery assembly. No 

significant conflicts in design or construction with the 

approval documents were noted. 

MSHA determined the block light system was the most 

likely ignition source for the 2nd massive explosion. The 

system consisted of two nonmetallic NEMA 4X enclosures 

with three lights and a photocell mounted in each, which 

were connected by long lengths of cable. The block lights 

were used to control traffic in a particular section of the mine. 

A miner would shine his caplamp onto the photocell to 

activate the traffic control lights in each box before 

proceeding. Fig. 1 is the block light circuit diagram 

replicated from the MSHA report appendix CC [2]. The 

system used 120 V for control signals and to power the lights. 

The boxes were connected by type SDT, 16 AWG, 12 

conductor, unshielded cable. Six conductors were used and 6 

were spare. Some conductors were connected to the line 

voltage and neutral. Fig. 1 shows no separate grounding 

conductor in the block light cable between the nonmetallic 

enclosures, or an equipment bonding jumper in the master 

enclosure for such a grounding conductor. No connections 

were shown for the spare conductors, suggesting they were 

not grounded. Usually slack cable connecting the master unit 

to the slave unit was rolled up and placed behind the slave 

unit to be unwound as the section, track, and ultimately the 

slave unit were advanced. 

The MSHA report included a section on root cause 

analysis. This section notes that underground electrical 

configurations should be reviewed to assure that their design 

or complexity would not confuse foremen or electricians, and 

unusual configurations should be made known to all persons 

working in the area. No enforcement action was taken with 

regard to the design of the electrical equipment. 30 CFR 

75.516-2 (b) indicates that communication cables must be 

protected against mechanical damage in a manner approved 

by the Secretary. MSHA did not interpret the block light 

cable installation as a violation of this requirement. The 

electrical equipment that provided the ignition sources for the 

explosions were not required to be permissible while in the 

intake-air course. 

IV. CLASS I HAZARDOUS LOCATIONS 

Certain techniques are used to design electrical equipment 

to protect against igniting explosions in locations where 

flammable materials may be encountered under normal or 

abnormal conditions. These locations are classified as 

Hazardous locations described in the National Electrical 

Code® (NEC®)

1

 [5]. NEC Article 500 describes Division 

locations while Article 505 describes Zone locations. The 

requirements for Divisions and Zones differ somewhat 

because the Division system was developed in the US while 

1 National Electrical Code® and NEC® are registered trademarks of the 

National Fire Protection Association, Quincy MA. 

the Zone system was developed in Europe. Zones were 

recognized in the NEC® beginning in 1996. NFPA 497 [6] 

and NFPA 499 [7] provide guidelines for classifying 

Hazardous Locations. 

The Hazardous Class refers to the flammable material; 

Class I materials are flammable gases and vapors (NEC 500.5 

(B)). Methane is a Class I Group D (Division system) or 

Class I Group IIA (Zone system) flammable material. Class I 

Group I (Zone system) refers to firedamp, defined as a 

mixture of gases, composed mostly of methane, found 

underground, usually in mines. NFPA 497 [6] provides 

guidelines for classifying flammable liquids, gases, or vapors. 

Class I Division 1 and Zone 1 locations are described in 

NEC 500.5(B)(1) and 505.5(B)(2). One description is a 

location in which equipment is operated or processes are 

carried on, of such a nature that equipment breakdown or 

faulty operations could result in the release of ignitable 

concentrations of flammable gas and also cause simultaneous 

failure of electrical equipment in a mode to cause the 

electrical equipment to become a source of ignition. A 

Division 1 or Zone 1 classification would be appropriate 

where common cause failures could release a flammable 

material and damage electrical equipment to produce an 

ignition source. Division 1 protection techniques include 

those familiar to the mining industry: explosion proof 

enclosures and two-fault intrinsic safety. Class I Division 1 

overlaps with Zone 0, which is a location where flammable 

gases or vapors are present continuously or for a long periods 

of time (NEC 505(B)(1)). 

One description of Class I Division 2 or Zone 2 is a 

location where ignitable concentrations of gases or vapors are 

normally prevented by positive mechanical ventilation, and 

which might become hazardous through failure or abnormal 

operation of the ventilating equipment (NEC 500.5(B)(2) and 

505.5(B)(3)). A rule of thumb for Division 2 or Zone 2 

equipment is that it should not be an ignition source under 

normal operation. Redundant safety features are generally 

not required. The safety justification for the equipment is 

that the explosion protection features are not likely to fail 

simultaneously with the infrequent process failure that 

releases the flammable material. The less redundant or robust 

features of Division 2 or Zone 2 equipment reflect the layer 

of protection already provided by the flammable material 

containment or ventilation system to prevent the flammable 

atmosphere from contacting the electrical equipment. 

One condition for Class I Zone 2 locations is that if a 

flammable atmosphere is released, it will exist only for a 

short period (NEC 505.5(B)(3)). A Class I Zone 2 restricted 

breathing enclosure, for example, will eventually leak, 

allowing a flammable concentration of gas to accumulate 

inside the enclosure if the enclosure is immersed in a 

flammable atmosphere for a long period of time. Magison 

[8] analyzes gas diffusion into sealed enclosures for 

explosion prevention purposes. The hermetically sealed 

contacts of a vacuum circuit breaker are another example of a 

sealed enclosure that is not an ignition source under normal 
Master Block Light Box 

1 2 3 4

EMI Signal

Conditioner 

120 VAC 

5A 5A 

20A 

Line 20A Power Center 

Neutral 120 VAC 

Ground 

Blk Line 

#16 AWG Wht Neutral 

3 Conductor Cable Grn Ground 

Power ON 

PLC Input 

I0.0 

I0.I 

Neut 

1A 

1 Blu 

Blu/Blk Photo 

Cell 

Slave Unit #1 

Photocell 

PLC Output 

Line 

Q0.1 

Q0.0 Red/Blk 

Yel/Blk 

Red 

Green 

2 Q0.2 1A Red Slave Unit #1 

Red Light 

Slave Unit #1 

Green Light 

Q0.3 1A Yel 3 

Q0.4 

Not Used 

Q0.5 

Not Used 

Q0.6 Org/Blk 

4 

1A Org 

Amber 

Slave Unit #1 

Amber Light 

L1 N1 

To Slave Unit #1 To Slave Unit #1 

L1 N1 

Yel #16 AWG 

Blu 12 Conductor Cable 

Blk 

Org 

Red 

Blk/Red 6 Used / 6 Spare 

4 N1 L1

Org 

Yel 

Red 

Blu 

Blk/Red 

Blk 

Slave Unit Block Light Box 

3 2 1 

L1 N1 

Power Optional ON 

Optional 

Photo 

Cell 

5A 

3 Green 

1A Org 4 Amber 

1A Yel 

5A 

1A Red 2 Red 

1 

1A Blu 

120 VAC 

Optional 

Fig. 1. Block light electrical circuit diagram. 
operation. For normal operation of electrical equipment in 

underground coal mines, an upper limit of the duration the 

equipment may be exposed to methane can be estimated 

based on the timing of required periodic methane checks. 

During emergencies however, battery powered equipment 

may be abandoned and exposed to methane for an extended 

period of time. More stringent protection would therefore be 

necessary for battery powered equipment abandoned during a 

mine emergency. Magison [8] explains Sealing and several 

other practices and principles for preventing explosions 

ignited by electrical equipment. 

These descriptions of Divisions and Zones reflect the 

situation found in intake air courses of gassy underground 

coal mines ventilated by fresh air where normally sparking 

electrical equipment is allowed to be used, and which may 

become flammable when the ventilation system fails. Fatal 

explosions in intake air courses ignited by electrical 

equipment have occurred numerous times in the past (Table 

1) [1]. Underground mines rely primarily on maintaining 

adequate ventilation and periodic methane checks to prevent 

explosions in intake air courses (30 CFR Part 75 Subpart D). 

Requirements for Division 2 or Zone 2 approved equipment 

imply that when lives are at stake, a good ventilation system 

should not be used in place of the protected equipment; 

rather, the protected equipment is a necessary layer of 

protection along with the ventilation system. 

V. BROOKWOOD IGNITION SOURCES ANALYSIS 

A. Block light installation 

Due to a series of events resulting from a roof fall and 

loss of ventilation, flammable gas migrated to damaged, slack 

cable near the block light slave unit, which most likely 

ignited the fatal second explosion. The flammable gas 

migrated to the unprotected equipment under infrequent, 

abnormal conditions when the ventilation system failed. This 

situation fits the NEC® description of a Class I Division 2 or 

Zone 2 hazardous location, which is a location where 

ignitable concentrations of gases or vapors are normally 

prevented by positive mechanical ventilation, and which 

might become hazardous through failure or abnormal 

operation of the ventilating equipment. 

The block light installation apparently did not meet 

several NEC® requirements for Class I hazardous locations. 

The installation of long lengths of slack, unsecured block 

light cable that became entangled and most likely provided 

the ignition source for the 2nd massive explosion may not 

have met 1999 NEC 501.11 which states that flexible cord 

used in a Class I Division 1 or 2 hazardous location is to be 

protected by location or a suitable guard from damage2

. 

Spare conductors in the unshielded block light cable 

apparently were not grounded. Fig. 1 shows no separate 

grounding conductor in the block light cable between the 

2 The 1999 edition of the NEC was the current edition at the time of the 

Brookwood disaster. NEC clause 501.11 was moved to clause 501.140 in 

the 2005 edition. 

nonmetallic enclosures, or an equipment bonding jumper in 

the master enclosure for such a grounding conductor. The 

1999 NEC 501.11 requires flexible cord to contain, in 

addition to the conductors of the circuit, a grounding 

conductor. The block light type SDT cable is not listed in 

NEC Table 400-4 as a type considered acceptable for extra 

hard usage. The 1999 NEC 501.11 requires flexible cord to 

be listed for extra hard usage. Robust protection provided by 

extra hard usage cord jacketing material combined with a 

grounding conductor and grounded spares inside the cord 

may have allowed a short to ground to activate the circuit 

protection fuse before the outer jacketing material was 

compromised, exposing the conductors to the flammable 

atmosphere (The 1999 NEC 501-6 provides requirements for 

fuses in Class I Division 1 and 2.). The live high voltage 

cable discussed above was determined not to be an ignition 

source for the first explosion for comparable reasons. 

Adherence to these NEC® requirements written specifically 

for preventing explosions may have prevented the massive 

second Brookwood explosion. 

B. Battery assembly 

The first explosion involving the battery assembly fits the 

description of Class I Division 1 or Zone 1, defined as a 

location in which equipment is operated or processes are 

carried on, of such a nature that equipment breakdown or 

faulty operations could result in the release of ignitable 

concentrations of flammable gas and also cause simultaneous 

failure of electrical equipment in a mode to cause the 

electrical equipment to become a source of ignition. The roof 

fall damaged the ventilation controls, released methane gas, 

and damaged the battery assembly so as to produce an 

ignition source. Also, there was no way of deenergizing the 

battery during the initial emergency, allowing the ignition 

hazard to persist while methane gas accumulated around the 

battery. The common cause failures produced by the roof fall 

and the persistence of the battery ignition hazard over time 

suggest the battery assembly should have been protected by 

Division 1 or Zone 1 techniques. 

MSHA found no significant problems with the battery 

assembly linked to the first explosion. 30 CFR Part 7 Subpart 

C lists federal requirements for battery enclosures. The 

United Mine Workers of America (UMWA) contend the 

battery enclosure was not well insulated, even though an 

insulation option was available from the manufacturer [3]. 

Following the disaster, the UMWA requested that such 

insulation be provided. The UMWA also requested 

installation of rubber conduit on all cables and leads, and 

support braces for the enclosure to protect the battery from 

damage from foreseeable roof falls. Extra structural support 

should take into consideration that manufacturers recommend 

opening the battery cover during charging to prevent the 

build-up of explosive hydrogen-air concentrations, and to 

provide cooling for the cells. The standard for the Zone 1 

protection technique “increased safety” calls for sufficient 

insulation between a battery enclosure and cells to prevent 
shorting [9]. The 30 CFR Part 7 requirements for battery 

assemblies should be reevaluated, taking into consideration 

the UMWA recommendations and “increased safety” 

requirements for battery assemblies. 

The UMWA also requested that gas detectors be placed 

near a power center and in a fresh air entry. These 

recommendations are in line with the Division 2 protection 

technique “Combustible Gas Detection System” called out in 

NEC 501.7 (K). The UMWA recognized the need to 

explosion protect equipment in fresh air locations susceptible 

to fugitive emissions of flammable gas, protections already 

enjoyed by workers in other industries. 

VI. HAZARDOUS LOCATION SURVEY 

Babiarz et al [10] conducted a survey of electrical cable 

vs. conduit usage in hazardous (classified) locations. About 

125 U.S. and Canadian electrical professionals responded to 

the survey. The respondents were employed at oil refineries, 

chemical plants, pulp and paper mills, or were consultants to 

these industries. Over 95% of the respondents represented 

heavy industry with electrical installations in hazardous 

(classified) locations. The respondents with hazardous 

(classified) locations reported 90% of their hazardous areas 

were classified as Division 2, compared to only 5% classified 

as Division 1. Division 1 protection techniques include those 

familiar to the mining industry: explosion proof enclosures 

and two-fault intrinsic safety. This survey demonstrates that 

Division 2 classified locations are common in North 

American industries at risk from fugitive emissions of 

flammable gas, except for underground coal mines. 

VII. BROOKWOOD VS. TEXAS CITY DISASTER 

Certain aspects of the Brookwood disaster can be 

compared to the BP refinery explosion in Texas City, TX on 

March 23, 2005, killing 15 workers [11]. The explosions for 

both disasters were ignited in locations where flammable 

gases or vapors occurred infrequently, but were foreseeable, 

and both fatal explosions were likely ignited by 

nonpermissible equipment. The possible ignition sources for 

the BP disaster were in locations probably less likely to be 

exposed to flammable atmospheres than working sections of 

gassy underground coal mines. OSHA cited BP North 

America for 167 egregious willful violations for using nonintrinsically safe electrical equipment in these locations. The 

proposed penalty for these electrical equipment violations 

alone was over $11 million. Civil lawsuits will likely involve 

much higher amounts. In contrast, MSHA did not issue any 

citations or make any recommendations in their root cause 

analysis with regard to the design of the electrical equipment 

that ignited both JWR explosions. Subsequently, fines of 

$435,000 were reduced to $3,000 after an administrative law 

judge ruled the company’s safety violations were minor [12]. 

VIII. ELECTRICAL REQUIREMENTS FOR SURFACE

COAL MINES 

Federal mining regulations for surface coal mines and 

surface work areas of underground coal mines require all 

wiring and electrical equipment to meet requirements of the 

NEC® in effect at the time of installation [30 CFR 77.516]. 

Such wiring and equipment would be subject to NEC® 

requirements for Division 2 locations, where applicable. 

Similar provisions are not found in 30 CFR Part 75 for 

underground coal mines. NEC® explosion protection 

requirements and techniques for Division 2 are recognized for 

surface locations of coal mines, but not for underground 

locations fitting the same criteria. 

IX. EMERGENCY SHUT DOWN PROCEDURES 

Federal regulations require that electrical power be shut 

off in an emergency such as occurred at Brookwood (30 CFR 

75.323). Mine workers did shut down the electrical power to 

the section where the second explosion occurred, however, 

the block light slave unit in the section remained energized 

for several reasons. Although the power to the section was 

disconnected, the block light slave unit was powered by a 

cable from another section. A later communications 

breakdown prevented the electrical power for the whole mine 

from being disconnected in time. One lesson from the 

Brookwood disaster may be that an orderly, manual 

shutdown of electrical power systems during the chaos of a 

mine emergency may not be a practical method of preventing 

explosions ignited by nonpermissible electrical equipment. 

Also, an unprotected electrical disconnect located near the 

source of gas release and activated during an emergency 

could provide the spark to ignite an explosion. Division 2 or 

Zone 2 protection techniques can provide a critical window 

of protection before all electrical power is shut down. 

X. RISK ASSESSMENT FOR EXPLOSION 

PROTECTED EQUIPMENT 

Although not recognized in the NEC® yet, a risk 

assessment approach for the acceptance of explosion 

protected equipment has been introduced by the International 

Electrotechnical Commission, Technical Committee 31 (IEC 

TC 31), as an alternative method to the current prescriptive 

practice linking equipment to Zones [13]. To facilitate this, a 

system of equipment protection levels (EPLs) has been 

introduced to indicate the inherent ignition risk of the 

equipment, no matter what type of protection is used. For 

coal mining, EPL Ma refers to equipment having a “very 

high” level of protection, which has sufficient security that it 

is unlikely to become an ignition source, even when left 

energized in the presence of an outbreak of gas. Typically, 

communication circuits and gas detection equipment would 

be constructed to meet the Ma requirements. EPL Mb refers 

to equipment having a “high” level of protection, which has 

sufficient security that it is unlikely to become an ignition 
source in the time span between there being an outbreak of 

gas and the equipment being de-energized. Typically all coal 

mining equipment would be constructed to meet the Mb 

requirements, for example flameproof motors and switchgear. 

The Instrumentation, Systems, and Automation (ISA) 

Society SP12 committee for Hazardous Location Equipment 

includes US Technical Advisory Groups (TAGs) for 

developing IEC TC 31 standards. The SP 12 committee also 

works toward US adoption of IEC explosion protected 

equipment standards. The ISA SP 12 committee recently 

established a mining working group to address explosion 

protected mining equipment. US equipment users and 

manufacturers are encouraged to participate in the process. 

XI. RECOMMENDATIONS 

The Brookwood disaster and other fatal mine explosions 

suggest intake air entries of gassy underground coal mines 

that might become hazardous through failure or abnormal 

operation of the ventilating system should be considered as 

certain Hazardous (classified) locations per the NEC®. Class 

I Division 2 or Zone 2 approved protection techniques should 

be used for non permissible intake-air electrical equipment 

that is likely to be de-energized during emergencies. Non 

permissible intake-air equipment that is likely to remain 

energized for extended periods during emergencies, such as 

battery powered equipment, should be protected by Class 1 

Division 1 or Zone 1 techniques at a minimum, for the sake 

of the rescuers. Flexible cords should be installed in 

accordance with 2005 NEC 501.140. The 30 CFR Part 7 

requirements for battery assemblies should be reevaluated, 

taking into consideration the UMWA recommendations and 

the Zone 1 “increased safety” standard requirements for 

battery assemblies. US mining equipment users and 

manufacturers are encouraged to participate with the ISA SP 

12 committee to develop and adopt internationally 

harmonized guidelines for explosion protected equipment. 

REFERENCES 

[1] T. H. Dubaniewicz Jr. “From Scotia to Brookwood, 

fatal US underground coal mine explosions ignited in 

intake air courses.” In preparation. 

[2] US Dept. of Labor, Mine Safety and Health 

Administration, Report of Investigation, Fatal 

Underground Coal Mine Explosions, September 23, 

2001, No. 5 Mine, Jim Walter Resources, Inc. 

Brookwood, Alabama. CAI-2001-20 through 32. Mine 

Safety and Health Administration, Arlington VA, 2002 

http://www.msha.gov/FATALS/2001/jwr5/jwr5home.ht 

m 

[3] Jim Walter Resources #5 Coal Mine Disaster, 

September 23, 2001; A United Mine Workers of 

America Report. United Mine Workers of America, 

Department of Health and Safety, Fairfax, VA, 2003 

http://www.umwa.org/brookwood/brookwood.shtml 

[4] Code of Federal Regulations, Title 30, Parts 1 to 199, 

Mineral Resources. U.S. Government Printing Office, 

Office of the Federal Register, Washington DC, 2006. 

http://www.msha.gov/30CFR/CFRINTRO.HTM 

[5] NEC®2005, NFPA 70: National Electrical Code®, 

International Electrical Code Series®, National Fire 

Protection Association, Quincy, MA, 2005. 

[6] NFPA 497: Recommended Practice for the 

Classification of Flammable Liquids, Gases, or Vapors 

and of Hazardous (Classified) Locations for Electrical 

Installations in Chemical Process Areas. National Fire 

Protection Association, Quincy, MA, 2004. 

[7] NFPA 499: Recommended Practice for the 

Classification of Combustible Dusts and of Hazardous 

(Classified) Locations for Electrical Installations in 

Chemical Process Areas. National Fire Protection 

Association, Quincy, MA, 2004. 

[8] E. C. Magison, Electrical Instruments in Hazardous 

Locations, 4th Ed. ISA, Research Triangle Park, NC, 

1998. 

[9] ANSI/ISA-60079-7 (12.16.01) Electrical Apparatus for 

Use in Class I, Zone 1 Hazardous (Classified) 

Locations: Type of Protection - Increased Safety "e",. 

ISA, Research Triangle Park, NC, 2002. 

[10] P. S. Babiarz, W. B. Delans and R. Hughes, “Cable or 

conduit - who uses it and why?” Record of Conference 

Papers, Industry Applications Society 44th Annual 

Petroleum and Chemical Industry Conference. Banff, 

Aberta September 15-17, 1997. IEEE catalog No. 

97CH36128, pp.129-134, 1997. 

[11] “OSHA Fines BP Products North America More Than 

$21 Million Following Texas City Explosion” US Dept. 

of Labor, Occupational Safety and Health 

Administration, National News Release: USDL 05­

1740. Washington, DC, 2005 

[12] S. Barancik, “Coal unit’s fines drop to $3,000” St. 

Petersburg Times, November 3, 2005. 

[13] IEC 60079-18 Ed. 3.0: Explosive Atmospheres – Part 

18: Equipment protection by encapsulation “m”. 

Committee Draft for Vote (CDV). International 

Electrotechnical Commission, Geneva, Switzerland, 

2007.