Development of a gas monitor 


simulator and mine rescue contest field trials
 

by D.W. Alexander, S.B. Bealko, J. Holtan, L.J. McWilliams and M. Whoolery 

D.W. Alexander, S.B. Bealko1

, 

1 Current position: Safety director, GMS Mine 

Repair and Maintenance, Oakland, MD 

members SME, and L.J. McWilliams 

are lead mining engineer, mining 

engineer, and surveillance team 

leader, respectively, at the National 

Institute for Occupational Safety 

and Health, Pittsburgh, PA. J. 

Holtan, member SME, is president 

of LightsOn Safety Solutions, The 

Woodlands, TX, and M. Whoolery is 

training director at MTTC, Prosperity, 

PA. Paper number TP-11-007. 

Original manuscript submitted 

February 2011. Revised manuscript 

accepted for publication July 2011. 

Discussion of this peer-reviewed and 

approved paper is invited and must 

be submitted to SME Publications by 

April 30, 2012. 

Abstract Researchers from the U.S. Office of Mine Safety and Health Research (OMSHR) of 

the U.S. National Institute for Occupational Safety and Health (NIOSH) completed field trials 

during coal mine rescue contests using simulated gas detectors in place of placards. The gas 

monitor simulator (GMS) devices replaced static, paper placards to deliver gas concentration 

data. Eleven teams were observed during the field contest, which was approved by the Mine 

Safety and Health Administration (MSHA). GMS devices were given to three team members 

(the captain and both gasmen). Observation of teams revealed that team members changed 

behavior by acknowledging and sharing information more often while using the GMS. As a result 

of this research, it has been demonstrated that under the existing contest format, the newly 

developed GMS device may be used with no adverse impact on team contest performance. 

Furthermore, when GMS technology advantages are used, contest realism is improved. In the 

future, competency assessment may be incorporated. 

Introduction 

The gas monitor simulator (GMS) 

is a new tool used to simulate gas monitoring with a handheld gas detector. 

Many improvements were made to the 

hardware and software since field testing the first prototype device in 2009 

(Bealko et al., 2010a).The GMS system 

includes wireless network routers, local 

communication protocol and singlepurpose GMS software running on 

Apple iPod Touch, iPhone or iPad devices that are used as simulated, handheld gas detectors. Each GMS detector 

can function as a trainer or student 

model. The trainer device is easily programmed with concentration data for 

three or four different gases, as needed 

for the training exercise. Hundreds of 

data points may be used. As a student 

approaches a placard, the trainer selects 

a gas reading on the training device, 

sends it through the Internet connection, and the student device displays 

the gas concentration. If the gas readings are above the alarm limits set by 

the trainer, the units give visual alarms 

(yellow, low alarm or red, high alarm) 

and audible alarms (different chime 

sounds). These alarms are similar to 

the alarms team members hear and see 

from their actual gas detectors. 

These GMS devices are designed 

to assist mine rescue team members 

in learning about gas detection, understanding the significance of gas concentrations and encouraging subsequent 

decision-making actions by team members. Moreover, using this tool eliminates the static practice of using printed 

gas readings on a cardboard placard 

(placed on the ground during training or contests) and replaces it with a 

more realistic method of receiving gas 

concentration readings — a simulated 

hand-held gas detector. 

Recent mine rescue team training 

events, contests and publications (Alexander et al., 2010) have highlighted the 

fact that training realism is important to 

the adequacy of team preparation for 

real emergencies.The 2006 Mine Safety 

Technology and Training Commission 

Report (Mine Safety Technology and 

Training Commission, 2006) states the 

following regarding mine rescue training quality, “We also find that training 

often is not realistic enough...” and 

“Many teams we spoke with emphasized the need for more rigorous and 

comprehensive training with respect to 
 

mine gases and the instruments used to detect them.” It is 

important to note that mine rescue teams are required to participate in two mine rescue contests per year (in accordance 

with Title 30 Code of Federal Regulations Part 49.20) and 

would do so whether or not this study was being conducted. 

Similar technology is used for training fire, hazmat and 

urban search and rescue teams (Bullex http://www.bullexsafety.com/hazmat.aspx and LightsOn Safety Solutions http:// 

www.lightsonss.com). The technology has been proven and 

used successfully in other industries. Our project goal is to 

determine if this technology intervention is effective in a 

mining context. This intervention, if effective and accepted 

by the mining industry, has the potential to improve the competency of mine rescue teams and individual miners. There 

are multiple company training events, more than 10 regional 

training centers (Bealko et al., 2010b) and approximately 30 

mine rescue contests conducted annually in the U.S. where 

these devices could be used (MSHA, 2010). International 

miner training groups have expressed interest in using the 

devices. 

The Office of Mine Safety and Health Research 

(OMSHR) of NIOSH contracted with LightsOn Safety Solutions (LightsOn-SS) to further develop the GMS to provide a more realistic miner training environment (Holtan, 

2010). The contract scope was to develop a miner-confined 

space entry and evacuation training program incorporating 

real-time gas detection simulation, scenarios and e-learning 

(Internet based) modules for student pretraining. This paper 

documents one activity conducted under that contract — to 

evaluate the GMS prototype device and software in a mine 

rescue contest situation. 

The purpose of this activity was to increase realism in 

mine rescue team training and contests by introducing a 

wireless hands-on gas detector simulator that can replace 

conventional paper placards. This evaluation was designed 

to compare usability, acceptance and suitability across two 

groups of mine rescue teams; one using the paper placards 

and one using the GMS.We observed team actions after team 

members received gas readings during contests and then 

conducted post-contest verbal debriefings with each team. 

Evaluation forms were completed by members of eight of the 

11 teams because three of the teams had to leave immediately following the exercise. This mine rescue team contest was 

run under the National Mine Rescue Rules by the Mining 

Technology and Training Center (MTTC), in Prosperity, PA. 

Field trial methodology 

A training research exercise was conducted on April 20 

and 21, 2010 to validate the OMSHR contract with LightsOnSS and to evaluate if mine rescue teams can and will use the 

GMS devices instead of the traditional method of placing paper placards on the ground or floor. Moreover, this exercise 

was designed to identify different actions of team members in 

response to receiving information from the GMS or placards. 

Observers noted the actions taken by team members following receipt of gas data to determine if behavior was affected 

by the method of delivery (GMS versus placard). 

The MTTC mine rescue skills competition includes eight 

events; of these, the simulated mine or field exercise was used 

for the evaluation.This field exercise requires the team to follow the National Mine Rescue Contest Rules (approved by 

MSHA) and the procedures they would follow in an actual 

mine rescue. The team is given a “problem,” which describes 

the mock emergency that is conducted in the aboveground 

simulated mine, and proceeds to carry out the “rescue” as 

required by the problem. 

One of the major issues associated with mine rescue competitions is that there must be a clear winner. Because of this, 

the organizers of the competition did not wish to interrupt 

the teams with time delays for the purpose of research any 

more than absolutely necessary. Therefore, novel teaching 

material available via the GMS hardware was not introduced, 

even though the GMS system was fully used during the contest for gas readings. This provided a great opportunity to 

observe the reaction from mine rescue team members with 

regard to simulated gas readings versus placards. 

Over a two-day period, 11 Division 1 (novice) and four 

Division 2 (experienced) mine rescue teams participated 

in the skills contest. The simulated underground mine was 

divided into two equal contest fields, so two exercises could 

be conducted simultaneously (Fig. 1). E

Figure 1 

The two indoor mine rescue training and contest fields are 

located in the new mine simulation building operated by the 

Mine Technology and Training Center. 

Figure 2 

These mine rescue team members are wearing breathing

apparatuses and using a GMS device that is displaying three

gases with high (red) and low (yellow) alarms. 

ach Division 1 and 2 

team had the same mine rescue field competition problem. 

The 11 Division 1 teams were scheduled on one field with 
a minimum of five teams assigned to each day’s competition. This schedule allowed consistent data collection by one 

OMSHR researcher observing all 11 teams. Division 2 teams 

were not included in the GMS/placard evaluation because of 

a concern that their more extensive contest experience might 

alter team behavior in a different way than the novice teams 

when receiving gas readings. 

Teams used the simulated gas detectors on both days. 

Three team members (captain and two gasmen) were trained 

to use the GMS gas detectors. Figure 2 shows an example 

of a mine rescue team member receiving a gas reading on 

the GMS device. The mine rescue problem required five gas 

readings at specified locations. Contest organizers were concerned that using the GMS for some teams would interfere 

with a fair contest, and that if the devices malfunctioned, 

the team would experience an unacceptable delay receiving the data. Therefore, dummy placards were used to note 

the location of where a gas reading would be provided, with 

the actual gas data on the underside in case of equipment 

failure. Use of dummy placards detracted from the potential 

improvement in realism when using a simulated device. In 

a real emergency, teams will not be warned where gas is located.Although not optimum,this methodology still allowed 

comparison of delivery mechanisms. Figure 3 shows examples 

of each of the placards used. 

Figure 3 

Mine rescue contest placards showing typical gas readings 

on the left and the dummy placard to indicate gas reading 

location on the right.
 

Immediately after the gas readings were received by the 

team members and recorded by the mapman, the OMSHR 

researcher recorded team actions (e.g., behaviors, sharing of 

information, next action, etc.). If the gas readings were above 

the alarm limits programmed into the GMS devices, the units 

gave visual and audible alarms. These alarms are similar to 

the alarms team members would receive from their actual 

gas detectors. No such warnings were provided to the teams 

using placards because placards are not interactive. 

Teams using placards were provided the same gas readings at the same specified locations as teams using GMS devices. OMSHR researchers observed these team members’ 

reactions to the gas placards and noted actions taken. Participants were encouraged to share their opinions regarding the 

gas data delivery method with researchers verbally or on the 

evaluation forms, but were not required to do so. 

These observations served to determine if the GMS aided 

or impeded the teams as they progressed through the simulated mine. The evaluations recorded team members’ perceptions of the exercise and whether they believed exercise 

realism to be improved or not. Each team was allowed 40 

minutes to complete the problem. A key objective was to 

determine if team members changed their behavior because 

of the gas data delivery method used. 

Data analysis 

Data were obtained during the MTTC PA Mine Rescue 

Skills Contest in three ways. First, the OMSHR researchers 

recorded on a paper form observations of team performance 

and times when gas readings were sent to compare to the 

GMS trainer device electronic Session Log available from 

the GMS software (Holtan, 2010). Second, the team members 

completed an evaluation form at the end of the day. Lastly, 

MTTC provided the contest results for analysis in the form 

of team scores for each skill demonstrated. 

Data Set 1. The paper data collection instrument is shown 

in Fig. 4

Figure 4
	

Mine rescue team data collection form.
 

. It is used to record demographic information on the 

participant and times (in hh:mm:ss format) for team actions 

in the same manner as the Session Log. 

Teams were observed to share more gas information 

between team members when using the GMS (four out of 

seven, or 57% of the teams, versus one out of five, or 20% 

of the teams) than when not using it. Placard team captains 

were often seen noticing the placard, relaying its existence to 

the mapman and passing it by without reading it. This action 

delegated communication of gas readings to the mapman 

and tail captain without the captain taking time to understand the gas concentrations. However, time was taken later 

to relay gas data from the mapman to the tail captain, who 

was anchored and could not see the placard. In the case of 

the GMS teams, the captain commented on the gas levels 

and the gasman showed the tail captain the readings on the 

device while other team members proceeded to explore. In 

all cases, the tail captain then relayed the gas information 

back to the briefing officer at the fresh-air base as the rules 

required, but no team used the gas readings to discuss their 

own safety during the contest. None of the teams in Division 

1 or 2 finished the problem. 

Teams noted placards ahead of their position and quickly 

directed their attention toward them as something of importance or as points of interest. Under contest conditions, teams 

are trained to minimize time to accomplish the exercise with 

the minimum deductions for rules violations.Team members 

apparently see the placard and know that it contains information. It is suspected that team behavior would change in contests without placards to identify locations of important data. 

Data Set 2. The second set of data was obtained from 

the team members by requesting voluntary completion of 

evaluation forms at the end of the training day. Not all teams 

or team members chose to complete the forms. To preserve 

confidentiality, names were not noted on the forms; however, 

team position and team names were recorded. 
 

The evaluation form included a place for comments 

concerning both the gas placards and simulated gas detectors. Team members provided no comments about placards. 

Handwritten comments were offered by 13 of the 36 GMS 

participants. The comments of five participants who mentioned the GMS are reproduced below and were generally 

favorable. One miner reported trouble getting readings reliably. Several indicated that the GMS made them practice as 

if they were using a real detector. 

•	 I really like the detectors.They were very helpful to the 

team to make gas checks. Good job! 

•	 Gas detector didn’t always work. 

•	 It’s an ok system, could be improved a bit. Gas readings could come in more places and info could come 

a bit sooner than right over the box or placard. That 

would make it more realistic. 

•	 Added time to receive readings added to realism. 

•	 The iPod worked out very well. Strongly advise the 

use of them. 

Table 1 

Mean scores and standard deviations by group. 

Group 1 

Mean 

Group 1 

Std Dev 

Group 2 

Mean 

Group 2 

Std Dev 

Group 3 

Mean 

Group 3 

Std Dev 

Q1 4.00 1.03 4.28 0.67 3.69 0.63

Q2 3.89 1.02 4.39 0.50 3.77 0.60

Q3 4.06 1.00 4.33 0.59 3.77 0.60

Q4 4.11 1.02 4.50 0.51 3.75 0.62

Q5 3.72 1.07 4.22 0.65 3.23 0.60

Q6 4.06 1.00 4.33 0.59 3.75 0.62

Q7 4.11 0.96 4.33 0.59 3.69 0.75

Table 2 

Results of Kruskal-Wallis (exact) test to compare responses among groups. 

Question Group 1 Mean 

Rank 

Group 2 Mean 

Rank 

Group 3 Mean 

Rank 

Pr > Chi-Square 

Q1 25.8 29.0 18.4 0.079

Q2 23.4 30.8 19.2 0.031 *

Q3 25.8 29.0 18.3 0.066

Q4 24.8 29.8 16.2 0.015 *

Q5 24.8 32.2 15.3 0.002 *

Q6 25.2 28.4 17.7 0.072

Q7 26.6 28.9 17.5 0.046 *

* Significant at p < 0.05 

The MTTC evaluation form also recorded comments on 

the gas detector as follows: 

•	 [I] like working in the smoke maze, and like the iPod 

for gas. 

•	 The iPod detectors (T-LOC) for gas in mine maze 

made it a lot easier and saved time. 

•	 I like the iPod 

•	 Exercises were very well planned out. Stations seemed 

to move well. Really liked the use of the iPods in the 

Sim-Mine. They really made the situation more realistic. Very good day. 

A statistical analysis of the MTTC questionnaire data was 

performed to determine if there was a difference in perception between the use of the placards and the GMS devices. 

Forty-nine evaluations were usable for the analysis and were 

divided into three groups. 

1.	 Team members who used the GMS (n = 18) 

2.	 Team members who did not use the GMS but were 

on teams that used the devices (n = 18) 

3.	 Team members who were not on teams using the 

GMS, but used placards (n = 13) 

The MTTC questionnaire consisted of seven questions 
(below) with a five-point Likert scale response: 1 = strongly 

disagree, 2 = disagree, 3 = neutral, 4 = agree, 5 = strongly 

agree. Table 1 shows the average values and their standard 

deviations for each question. All responses are greater than 

neutral and many of those using the GMS are between agree 

and strongly agree. Because the data values only represented 

ordered categories, the Kruskal-Wallis test, a nonparametric 

(distribution-free) test for k independent samples, was used 

to compare the median scores among the three groups. This 

nonparametric test analyzes the ranks of a variable rather 

than its original values. When the data are classified into 

more than two groups, the test is on the one-way ANOVA 

statistic.When a statistically significant difference was found, 

then all possible two-group comparisons were conducted to 

examine the source of the difference (group 1 versus group 

2, group 1 versus group 3, group 2 versus group 3). 

The seven questions were as follows: 

1.	 I feel more confident about taking gas readings in a 

real emergency after this mine rescue problem. 

2.	 Because of the way I received the gas concentrations 

today, I think I can deal with the changing gas data 

and take appropriate action. 

3.	 My ability to use the gas detector in a real emergency 

improved because of the practice I got today. 

4.	 The way we received the gas readings increased the 

realism of the exercise. 

5.	 I would like to have more information about what 

the gas readings mean as I work the problem. 

6.	 The gas data was delivered clearly to me. 

7.	 The gas data related well to the problem. 

The statistical analysis was conducted using SAS v.9.2 

(SAS Institute Inc., Cary, NC). Due to the limited sample 

size, exact nonparametric tests were computed. Results were 

considered statistically significant if the p-value of the test 

was < 0.05 for the three-group comparisons. To account for 

multiple comparisons, the p-value for the two-group tests was 

adjusted to < 0.02 using the Bonferroni correction, where 

the α level is divided by the number of comparisons (0.05/3). 

The results of the Kruskal-Wallis test are presented in 

Table 2. Significant differences among the groups were found 

for questions 2, 4, 5 and 7 (bold type in the list above). The 

comparisons between group 2 (team members who did not 

use the GMS, but were on teams with the GMS) and group 3 

(team members on teams using the placards) were all significantly different for these four questions, with the mean rank 

consistently higher for group 2. 

Questions 1, 3 and 6 relate to the person actually taking 

gas readings. Since neither group 2 nor group 3 took actual or 

simulated gas readings, these questions would tend to show 

little difference in ranking. The significantly more favorable responses given by group 2 indicates that even though 

they did not have the GMS device, the increased discussion 

between members of the team that did have the GMS, as 

observed by the OMSHR researchers, or the improved realism (questions 4 and 7) affected their understanding of the 

situation. Question 2 indicates an increase in self-confidence. 

Question 7 suggests that use of a simulated gas detector in 

place of placards promoted realism. The interest expressed 

by the high score of question 5 by group 2 may indicate that 

these team members are ready to take the next step in skills 

training to achieve greater understanding of their situation 

in spite of the time demands of a contest environment, or 

that they would like to have more analysis and information 

provided by or through the device. It is interesting that group 

1, who carried the GMS device, did not have a statistically 

and significantly different mean rank from either group 2 or 

group 3 for any of the questions. However, group 1 scores 

were higher than group 3 for all questions. This may mean 

that the process of reading and recording gas data occupied 

their time or that they may already be confident in their 

gas reading abilities, whereas the team members in group 2 

would be expected to agree more positively that their abilities were improved by this exposure. 

Data Set 3. A third set of data were obtained by totaling 

the B card and Map category scores from the judges’ summary score sheets for each team (these categories include gas 

detection criteria in the mine exercise).Time discount scores 

were not recorded because no team finished the problem. 

Eleven Division 1 teams earned the scores shown in Table 3. 

Table 3 

Division 1 mine rescue exercise scores ranked from fastest 

to slowest with gas data delivery method. 

Team Total minutes Device 

1 138 Placard 

2 153 GMS

3 157 GMS

4 157 Placard 

5 161 Placard 

6 168 GMS

7 175 GMS

8 180 GMS

9 185 Placard 

10 220 GMS

11 241 GMS

These scores are shown in rank order from the shortest time 

to the longest. 

The distribution of scores is not biased according to the 

gas reading delivery method. All the teams using GMS are 

not distributed evenly at either extreme of the scoring, which 

appears to indicate that the gas reading delivery method did 

not affect the skills contest results. Thus, the GMS had neither a beneficial or deleterious effect on the winning teams. 

However, no statistically definitive conclusion on non-randomness could be reached, due to the small sample size. 

Local contest plan with GMS 

Figure 5 shows a typical indoor mine rescue practice and 

contest field that is three entries wide and five entries deep, 

with coal blocks painted on the floor (Alexander et al., 2010). 

Similar practice fields are used for local contests when held 

inside or outside on larger grass areas. The GMS system can 

host multiple independent trainer/student groups simultaneously. Therefore, two, three or 10 teams could compete at 
the same time using GMS devices to deliver simulated gas 

concentration data. 

Contests could be conducted using a gas detector simulator similar to the GMS or the Bullex units. No placards for 

gas data would be required. The trainer would follow the 

team and send gas readings according to a predetermined 

plan to correspond to the simulated mine environment. 

Teams would have to decide what data to record on their 

maps and communicate to the fresh-air base briefing officer. 

The scenario could be designed to make team safety an issue. 

For example, knowledge of gas hazards would allow the team 

to solve a team safety problem and demonstrate competency. 

Judging could still be conducted uniformly, as long as gas 

sampling best practices were defined in the rules. 

The GMS “instant messaging feature” allows the trainer 

to send text messages to mine rescue students during an exercise. The GMS Session Log records all messages. The messages may provide additional information, ask questions of 

one or all students, or give instructions.This allows the trainer 

to provide further insight into the significance of the particular gas reading or to verify that the student understands the 

issue when a response is requested. It was not used during 

the MTTC skills competition because this would have introduced differences between delivery methods and interfered 

with the approved contest protocol. However, in future skills 

training or competency “contests,” the use of this feature 

could document student understanding of the material, provide a traceable record of student performance and allow the 

trainer to coach individual students or the team during the 

exercise, when it will have the greatest relevancy. 

Figure 5 

The indoor mine rescue/contest practice field at Consol 

Energy’s Buchanan Mine training facility. 

Summary and recommendations 

NIOSH/OMSHR researchers completed field trials of 

coal mine rescue team contest practices using simulated 

gas detectors in place of placards for seven of the 11 teams 

observed during the contest. GMS devices were given to 

three team members: the captain and both gasmen. They 

replaced static, paper placards to deliver gas concentration 

data with no apparent adverse impact on the team contest 

performance. 

As a result of this research, it has been demonstrated that, 

under the existing contest format, gas monitoring simulation 

devices may be used whenever desired by the contest organizers and approved by MSHA. According to participants, 

when this technology is used, contest realism is improved. 

Teams were observed to change behavior and share information more often while using the GMS system, which is 

believed to lead to better understanding of the gas hazards 

encountered in an emergency event and a greater awareness 

of team safety. 

Use of the GMS-type devices to simulate the presence of 

hazardous gases during mine rescue team contests or training allows participants to experience a more real-life environment, which is not available without exposing them to 

unacceptable risk. Companies are experimenting with using 

gas detector simulators in training mine rescue teams, fire 

brigades, foremen and new miners. International training 

groups have expressed interest in the technology. 

Further research is needed to evaluate the level of team 

recognition of hazardous situations and decision-making 

needed to protect team safety. The authors believe that the 

technology will be used in place of placards for a multifield, 

local contest in the near future. Another possible venue for 

the GMS is the expanding field of virtual reality miner training. 

Acknowledgments 

The data collection would not have been possible without 

the assistance of NIOSH/OMSHR technicians Linda Chasko 

and Donald Sellers and the cooperation of the MTTC staff, 

MSHA, mine rescue team members participating in the 2010 

Mine Rescue Skills Competition and the Pennsylvania,West 

Virginia and Ohio state mine rescue trainers. 

Disclosure 

The findings and conclusions in this report are those of 

the author(s) and do not necessarily represent the views of 

the National Institute for Occupational Safety and Health 

(NIOSH). Mention of any company or product does not 

constitute endorsement by NIOSH. In addition, citations to 

Web sites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs 

or products. Furthermore, NIOSH is not responsible for the 

content of these Web sites. All Web addresses referenced in 

this document were accessible as of the publication date. 

References 

Alexander, D.W., Bealko, S.B., Brnich, M.J., Kowalski-Trakofler, K.M. and 

Peters, R.H., 2010, Best Practices for Escape and Rescue from Underground Coal Mines, Pittsburgh, PA: U.S. Department of Health and 

Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and 

Health, DHHS (NIOSH), #IC-9522 (in revision). 

Bealko, S.B., Alexander, D.W., Chasko, L.L., Holtan J., 2010a, “New simulated gas detector offers realistic training for mine rescue teams,” 13th 

United States/North American Ventilation Symposium, 2010, Hardcastle & McKinnon (eds.) © MIRARCO, June 2010. 

Bealko S.B., Alexander D.W., Chasko L.L., Grayson R.L., 2010b, “A global 

inventory of mine rescue training facilities – compendium of ideas to 

improve U.S. coal mine rescue training,” SME Annual Meeting Preprint 09-101, Phoenix, AZ, February 2010. 

Holtan, J., 2010, “Develop a miner confined space entry and evacuation 

training program incorporating real-time gas detection simulation, 

scenarios, and theoretical E-Learning,” Final Report, LightsOn Safety 

Solutions, NIOSH Contract Number 200-2009-32458, Pittsburgh, PA, 

August 2010, available at http://lightsonss.com/category/publications/. 

Mine Safety Technology and Training Commission, 2006, “Improving mine 

safety technology and training: establishing U.S. global leadership,” 

December 2006, pp. 55-77. 

MSHA, Mine Safety and Health Administration, MSHA’s Mine Rescue 

Contest Home Page, http://www.msha.gov/MineRescue/CONTEST. 

htm, Date accessed September 2010.