Report of Investigations 9656 

Self-Contained Self-Rescuer Field Evaluation: 

Seventh-Phase Results 

Nicholas Kyriazi and John P. Shubilla 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
 Centers for Disease Control and Prevention
 

National Institute for Occupational Safety and Health
 

National Personal Protective Technology Laboratory
 

Pittsburgh, PA
 

March 2002 
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DHHS (NIOSH) Publication No. 2002-127 
CONTENTS
 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Page 

1 
 

Introduction ................................................................................... 2 
 

Experimental procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 
 

Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
 

CSE SR-100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
 

Draeger OXY K-Plus ......................................................................... 5 
 

MSA Life-Saver 60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 
 

Ocenco EBA 6.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 
 

Ocenco M-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 
 

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 
 

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 
 

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 
 

ILLUSTRATIONS 

1. Breathing and metabolic simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

 2. Cased and uncased CSE SR-100 self-rescuer .................................................... 2 
 

3. Cased and uncased Draeger OXY K-Plus self-rescuer ............................................. 3 
 

4. Cased and uncased MSA Life-Saver 60 self-rescuer ............................................... 3 
 

5. Cased and uncased Ocenco EBA 6.5 self-rescuer ................................................. 3 
 

6. Cased and uncased Ocenco M-20 self-rescuer ................................................... 3 
 

7. CSE SR-100 test results ..................................................................... 6 
 

8. Draeger OXY K-Plus test results .............................................................. 7 
 

9. MSA Life-Saver 60 test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 
 

10. Ocenco EBA 6.5 test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 
 

11. Ocenco M-20 test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 
 

12. CSE SR-100 decibel level versus CO2 level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 
 

TABLES 

1. SCSRs collected for evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 
 

2. BMS and human-subject metabolic parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 
 

3. Wilcoxon rank-sum test results ............................................................... 4 
 

4. CSE SR-100 CO2 breakthrough times .......................................................... 5 
 

5. Ocenco M-20 CO2 breakthrough times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 
 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

breaths/min breaths per minute L/min liter(s) per minute
 

hr hour(s) min minute(s)
 

kg kilograms(s) mL/min milliliter(s) per minute
 

L liter(s) mm H2O millimeter(s) of water (pressure) 

L/breath liter(s) per breath ppm parts per million 
SELF-CONTAINED SELF-RESCUER FIELD EVALUATION: 

SEVENTH-PHASE RESULTS
 

By Nicholas Kyriazi1

1

Biomedical engineer.
 

and John P. Shubilla2 

2

Engineering technician.
 

National Personal Protective Technology Laboratory, National Institute for Occupational Safety and Health, Pittsburgh, PA.
 

ABSTRACT 

The National Institute for Occupational Safety and Health, National Personal Protective Technology 

Laboratory, has undertaken a study to determine how well self-contained self-rescuers (SCSRs), deployed in 

accordance with Federal regulations (30 CFR 75.1714), hold up in the underground environment with regard 

to both physical damage and aging. This report presents findings regarding laboratory-tested SCSRs in the 

seventh phase of testing from May 1999 to August 2000. The SCSRs were tested on human subjects and on 

a breathing and metabolic simulator. The results indicate that most of the apparatus, if they pass their approved 

inspection criteria, perform satisfactorily. The deployed CSE SR-100s, however, exhibited significantly higher 

inhaled carbon dioxide (CO2) levels than new units, as they did in the previous two phases. Several Draeger 

OXY K-Pluses that rattled when shaken were found to have potassium superoxide (KO2) particles throughout 

the breathing circuit, including the mouthpiece. Draeger investigated the problem and developed a shake test 

to detect damaged units. The durations of new Ocenco M-20s were statistically significantly longer than those 

of deployed units, although only by 2 min. 
2 

INTRODUCTION
 

On June 21, 1981, U.S. coal mine operators were required to 

make available to each underground coal miner a self-contained 

self-rescuer (SCSR). The regulations (30 CFR 75.1714) require 

that each person in an underground coal mine wear, carry, or 

have immediate access to a device that provides respiratory 

protection with an oxygen (O2) source for at least 1 hr, as 

approved by the certifying agencies—the National Institute for 

Occupational Safety and Health (NIOSH) in Morgantown, WV, 

and the Mine Safety and Health Administration (MSHA). The 

NIOSH National Personal Protective Technology Laboratory 

(NPPTL) and MSHA are conducting a long-term evaluation of 

SCSRs deployed in underground coal mines. NPPTL locates 

mines willing to participate in the study and trades deployed 

SCSRs for new ones in cooperation with MSHA. NPPTL then 

tests the deployed SCSRs. The objective of this program is to 

evaluate the in-mine operational durability of deployed SCSRs. 

Of utmost concern is the successful performance of any SCSR 

that passes its approved inspection criteria. Such apparatus 

must function successfully to enable a miner to escape safely 

during a mine emergency. Apparatus that fail inspection are 

expected to be removed from service. 

EXPERIMENTAL PROCEDURE
 

This study involves testing approximately 100 SCSRs in 

each phase. This report describes findings in the seventh phase 

of testing from May 1999 to August 2000. Previous reports 

describe phases 1 through 6 [Kyriazi et al. 1986; Kyriazi and 

Shubilla 1992, 1994, 1996, 2000]. Ninety percent of the 

apparatus were tested on a breathing and metabolic simulator 

(BMS) (figure 1) and 10% on human subjects on a treadmill. 

Figure 1.—Breathing and metabolic simulator. 

MSHA supplies some of the human test subjects from its Mine 

Emergency Unit for treadmill testing. 

The SCSRs tested were manufactured by CSE Corp., 

Draegerwerk AG, Mine Safety Appliances Co., Inc. (MSA), and 

Ocenco, Inc. They were sampled according to estimated market 

share (table 1). The apparatus are shown in figures 2 through 6. 

Table 1.—SCSRs collected for evaluation 

Apparatus Market 

share 

No. received

and tested 

CSE SR-100 . . . . . . . . . . 46 46 

Draeger OXY K-Plus . . . 5 10 

MSA Life-Saver 60 . . . . . 7 11 

Ocenco EBA 6.5 ....... 39 30 

Ocenco M-20 . . . . . . . . . 

 Total . . . . . . . . . . . . . . 

2 10

— 107 

The O2 constant-flow rate is checked on the Ocenco EBA 

6.5, a compressed-O2 apparatus. The NIOSH-required flow is 

1.5 L/min at ambient temperature and pressure (at NIOSH in 

Morgantown, WV), dry (ATPD). 

All apparatus in this study are checked for breathing circuit 

leak tightness after opening. The leak test used is that 

recommended by Draeger for its BG-174A rescue breathing 

Figure 2.—Cased and uncased CSE SR-100 self-rescuer. 
3 

apparatus. It is performed to determine how well the apparatus 

isolates the user from the environment, which may be irrespirable in an emergency. Passing this test is not a requirement of the current regulations for these apparatus, however. 

The test permits a decay in breathing circuit pressure from -70 

to -60 mm H2O in 1 min. We have determined that just passing 

the test is equivalent to a leak rate of approximately 1 mL/min 

given an internal volume for both the apparatus and test stand of 

1 L (all volumes in this report are given at standard temperature 

(0o C) and pressure, dry, unless otherwise noted). To give this 

some perspective, an in-leakage rate of 87 mL/min in a 10% CO 

atmosphere at a peak inhalation flow rate of 250 L/min will 

result in the 8-hr threshold limit value (TLV) for CO of 35 ppm. 

The 250 L/min peak inhalation flow rate is used because this 

occurs at roughly an 80 L/min ventilation rate, the highest likely 

such rate that can reasonably be expected of a user. At such a 

maximal work rate, inhalation pressure should not exceed 

-300 mm H2O, the highest negative pressure tolerated by 80% 

of test subjects in a recent study [Hodgson 1993]. At the leak 

test pressure of -70 mm H2O, the proportional in-leakage rate 

resulting in the 8-hr TLV would be 20 mL/min at a peak 

inhalation flow rate of 58 L/min. The Draeger leak test, 

therefore, can be considered very conservative when applied 

under these circumstances. 

 Figure 3.—Cased and uncased Draeger OXY K-Plus selfrescuer. 

Figure 4.—Cased and uncased MSA Life-Saver 60 self-rescuer.

Figure 5.—Cased and uncased Ocenco EBA 6.5 self-rescuer. 

Figure 6.—Cased and uncased Ocenco M-20 self-rescuer. 

NPPTL selected the participating mines with regard to type 

of mining operation, coalbed height, and SCSR deployment 

mode in order to obtain a wide range of deployment impact. 

Deployment modes included permanent storage on the ground, 

on a mantrip or mining machine, or belt-worn. 

The BMS test consisted of the average metabolic work rate 

exhibited by the 50th-percentile miner weighing 87 kg while 

performing the 1-hr man test 4 as described in 42 CFR 84. 

However, even though the average work rate is the same, 

NPPTL testing is not equivalent to the certification testing at 

NIOSH-Morgantown. The certification testing imposes high 

and low work rates that the average, used at NPPTL, does not. 

Also, the stressor levels are continuously monitored at NPPTL, 

whereas they are sampled only between work activities in the 

certification testing. In addition, NPPTL testing continues until 

the apparatus is empty, whereas testing during certification ends 

at a predetermined time—the rated duration—even though the 

capacity of the apparatus usually exceeds this, sometimes 
4 

considerably. Therefore, an apparatus that fails NPPTL testing 

would not necessarily fail certification, and vice versa. In the 

treadmill testing, the human subjects walked at whatever speed 

and grade resulted in an O2 consumption rate of 1.35 L/min. 

The CO2 production rate, ventilation rate, and respiratory 

frequency varied in the test subjects. The metabolic parameters 

for both BMS and human subjects are given in table 2. 

Table 2.—BMS and human-subject metabolic parameters 

Metabolic workload BMS Subject A Subject B Subject C 

O2 consumption rate . . . . . . . . . . . . . L/min . . 1.35 1.35 1.35 1.35 

CO2 production rate . . . . . . . . . . . . . L/min . . 1.15 1.12 1.18 1.00 

Ventilation rate . . . . . . . . . . . . . . . . . L/min . . 30.0 27 22 28 

Tidal volume . . . . . . . . . . . . . . . . . L/breath . . 1.68 1.59 2.20 2.00 

Respiratory frequency . . . . . . breaths/min . . 17.9 17 10 14 

Peak respiratory flow rate:

 Inhalation . . . . . . . . . . . . . . . . . . . L/min . . 

 Exhalation . . . . . . . . . . . . . . . . . . . L/min . . 

89 

71 

(

1

) 

(

1

) 

(

1

) 

(

1

) 

(

1

) 

(

1

) 1

Not measured. 

 The 

BMS CO2 production rate was lowered in this phase of testing 

to 1.15 L/min from 1.30 L/min in the last two phases to better 

match the average rate of the human test subjects currently used 

in the study. 

The parameters monitored were inhaled levels of CO2 and 

O2, end-of-inhalation wet- and dry-bulb temperatures, and 

inhalation and exhalation peak breathing pressures in both the 

BMS and treadmill testing. In the BMS testing, however, 

average inhaled levels of gas concentration were measured as 

opposed to the minimum values of CO2 and maximum values of 

O2 in the treadmill testing. Average inhaled gas levels include 

the effect of apparatus dead space, whereas minimum values of 

CO2, for example, are only the lowest level of gas concentration 

during inhalation. The BMS measures average inhaled values 

by electronically summing all of the CO2 and O2 over each 

inhalation cycle, weighted by the instantaneous flow rate. The 

BMS also measures minimum inhaled CO2 levels. 

Tests on the BMS were terminated upon exhaustion of 

the O2 supply as indicated by negative pressures reaching 

-200 mm H2O coinciding with an empty breathing bag. If 

average inhaled CO2 levels exceed 10% or O2 levels fall below 

15%, the accuracy of the metabolism of the BMS becomes 

questionable, and tests were terminated at those points or shortly 

afterward. Treadmill tests were terminated when the O2 supply 

was exhausted, if minimum inhaled CO2 exceeded 4%, if 

maximum inhaled O2 fell below 15%, or if the test subject 

stopped because of subjectively high breathing pressures or 

temperatures. 

The Wilcoxon rank-sum test was performed for each 

monitored stressor to determine whether or not the deployed 

units behaved differently from new units. It tests the hypothesis 

that the two samples are from populations with the same mean. 

The values from both samples are ranked in ascending order of 

magnitude. If the sum of the ranks of the smaller sample (T) 

(in this case, new units) falls within the acceptable range for the 

given sample sizes, then there is not sufficient evidence at the 

specified probability level (" =.05, two-sided) to say that the 

means of the two samples differ. The rank-sum test does not 

rely upon the assumptions that either the new- or deployed-unit 

data are normal distributions or that they have identical 

variances, as does the t-test for two populations of independent 

samples. One limitation of the Wilcoxon rank-sum test is that 

it does not distinguish between large and small differences in 

values. The results of the two-sided, " = 0.05, Wilcoxon ranksum tests are presented in table 3. 

Table 3.—Wilcoxon rank-sum test results 

Apparatus Duration

Range T 

Average 

inhaled CO2 

Range T 

Average 

inhaled O2 

Range T 

Wet-bulb 

temperature 

Range T 

Dry-bulb 

temperature 

Range T 

Inhalation 

pressure 

Range T 

Exhalation

pressure 

Range T 

SR-100 . . . . . . . 15-60 42 15-60 4 15-60 45 15-60 66 15-60 63 15-60 34 15-60 46 

OXY K-Plus . . . 8-31 25 8-31 22 8-31 29 8-31 22 8-31 24 8-31 22 8-31 18 

Life-Saver 60 . . 9-33 21 9-33 16 9-33 16 9-33 25 9-33 28 9-33 16 9-33 19 

EBA 6.5 ...... 18-75 32 18-75 26 18-75 70 18-75 46 18-75 62 18-75 36 18-75 20 

M-20 . . . . . . . . . 8-31 33 8-31 20 8-31 16 8-31 27 8-31 31 8-31 22 8-31 8 

T ' Sum of the ranks of the smaller sample (new units). 

The probability of T falling 

outside the given range is 0.05 if the populations have the same 

mean. 
5 

RESULTS AND DISCUSSION
 

Experience with each model of apparatus is discussed 

separately. The minute-average values of the monitored 

stressors were averaged over the entire test duration and are 

presented graphically (figures 7-11) for each apparatus by 

stressor. The values for new units tested on the BMS can be 

compared with those for deployed units tested on the BMS and, 

to some extent, with those for deployed units tested on human 

subjects on a treadmill, which are plotted afterward. Because 

human subjects may differ from each other and from the BMS 

in terms of CO2 production rate, ventilation rate, and respiratory 

frequency, all of which affect apparatus duration as well as all 

of the monitored stressors, treadmill tests cannot be considered 

equivalent to the BMS tests even though the O2 consumption 

rate is the same. Missing data points for wet-bulb temperature 

indicate equipment malfunction or inability to instrument 

apparatus. 

CSE SR-100 

In addition to the 40 apparatus targeted for collection in this 

phase, we tested an additional 6 units received from the United 

Mine Workers of America, at their request, for a total of 

46 SR-100s. 

Of 44 deployed units checked for breathing circuit leaks, 

34 passed. Two of the three new apparatus checked for leaks 

passed. 

As in the previous two phases, the Wilcoxon rank-sum test 

[M=3; N=21] for average inhaled CO2 showed a significant 

difference between new and deployed units, with deployed units 

having higher values than new ones (table 3). CSE's noise test, 

developed to detect bed degradation, was not being used at the 

mines during the collection of all the apparatus in this phase of 

testing. Therefore, some apparatus were collected that had noise 

levels that would have required them to be removed from 

service. They were tested anyway to see how they performed. 

In general, the higher the decibel level, the higher the CO2 level; 

however, the correlation coefficient was only 0.51 in this phase 

versus 0.85 for 17 apparatus tested in the previous phase. We 

have no explanation for this disparity at present but, for the 

apparatus tested here, only when decibel levels were under 34 

was one guaranteed that average inhaled CO2 levels would 

remain under 4% during the life of the unit (figure 12). 

Table 4 shows that 15 of 42 apparatus tested on the BMS 

experienced CO2 breakthrough before expenditure of the O2 

supply; 11 of these occurred before 60 min. 

Table 4.—CSE SR-100 CO2 breakthrough times, minutes 

Type of unit and 

test method 

CO2 

breakthrough 

time 

Test 

duration 

Maximum 

CO2 

Deployed: BMS . . . . . 59 

56 

60 

58 

4.4 

5.0 

58 62 6.0 

15 65 12.2 

12 63 10.2 

57 63 6.2 

55 61 7.4 

60 61 4.0 

58 66 9.6 

64 65 4.5 

57 63 5.5 

66 66 4.2 

49 60 8.0 

58 64 7.2 

66 68 4.7 

Deployed: Human

 subject on treadmill 50 

49 

52 

49 

4.3 

4.6

 CO2 breakthrough for BMS - 4% average inhaled; for treadmill - 4% 

minimum inhaled. 

None of the new 

units experienced premature breakthrough. The response to 

high inhaled levels of CO2 will be increased ventilation rates in 

most users. Increased ventilation rates will result in higher 

breathing pressures experienced by the user. Breathing 

resistance in the SR-100 increases rapidly toward end-of-life 

even in new apparatus, and elevated CO2 levels will only add to 

this. 

The Wilcoxon rank-sum test also shows that new units had 

statistically significantly higher wet- and dry-bulb temperatures 

than deployed units. This may be a reflection of more complete 

reaction of the bed chemicals in new units. 

Three units had no or insufficient starter oxygen, requiring a 

manual start before beginning or shortly after beginning the test. 

There were five instances of either the top, bottom, or both lids 

being particularly hard to remove. These occurrences were all 

in apparatus manufactured prior to March 1992; a part change 

in late 1994 was designed to prevent this problem. Two of the 

four units used in human-subject tests caused coughing upon 

donning. One of the test subjects reported burning at the back 

of his throat in addition to coughing. As a result, 10 breaths 

were exhaled into the unit to wet down the offending dust 

(presumably corn starch, which is used by the manufacturer to 

keep saliva from reaching the chemical bed), after which testing 

continued normally. Two BMS tests were terminated due to 

breathing pressures that exceeded the range of the pressure 

transducer (700 mm H2O). All of the others were terminated 

with flat bags or high CO2 (table 4). 

DRAEGER OXY K-PLUS 

Two deployed units passed the leak-tightness test and seven 

failed; two new units passed the test and one failed. 

The Wilcoxon rank-sum tests [M=3; N=9] for the Draeger 

show that new units could not be distinguished from deployed 

units in any measured parameter. 

No deployed or new units experienced CO2 breakthrough. 

No problems were evident in the 10 apparatus from the 

targeted sample. However, a mine using both CSE SR-100s and 
6 

Figure 7.—CSE SR-100 test results. 
7 

Figure 8.—Draeger OXY K-Plus test results. 
8 

Figure 9.—MSA Life-Saver 60 test results. 
9 

Figure 10.—Ocenco EBA 6.5 test results. 
10 

Figure 11.—Ocenco M-20 test results. 
11 

Draeger OXY K-Pluses decided to try the CSE shake test on its 

Draeger units and found that some of them rattled. The mine 

expressed concern to MSHA, which asked us to inspect five of 

these apparatus. We found that some of the apparatus had 

leaked KO2 into the breathing circuit on both sides of the 

canister—inside both the breathing bag and breathing hose. 

Three of these units were missing the metal plates on which are 

written the serial number and manufacturing date, and which 

contain the belt loops. These apparatus, therefore, did not pass 

inspection. Some of the units that had KO2 leakage, however, 

did pass inspection and, as a result, an investigation by NIOSH, 

MSHA, and Draeger was undertaken. Draeger has developed 

a shake test for the OXY K-Plus. 

Figure 12.—CSE SR-100 DB level versus CO2 level. 

MSA LIFE-SAVER 60 

Nine of the eleven deployed units passed the leak test; all 

three of the new units passed. 

The Wilcoxon rank-sum tests [M=3, N=10] show that new 

units did not perform differently from deployed units in any 

performance measure. 

No deployed or new units experienced CO2 breakthrough. 

The low oxygen level during the treadmill test (figure 9) was 

caused by a poorly fitting nose clip on the human test subject. 

One unit had a small slit in the breathing bag. An inspection 

by NIOSH, MSHA, and MSA of approximately 100 units 

produced over the same time period revealed no further similar 

damage. It was determined that the isolated case was a 

manufacturing defect. Although the unit behaved normally in 

the BMS test, it must be assumed that any breach in the 

breathing circuit is a serious defect that can admit toxic gases 

into the breathing circuit. A hole in the breathing bag, however, 

is likely to admit a smaller quantity of ambient air into the 

breathing circuit than a hole in the inhalation hose, for example, 

since the pressure in the bag is usually very close to ambient 

pressure, whereas the inhalation hose will see greater negative 

pressures. 

One deployed unit had a large dent on its lid, which required 

it to be removed from service. It was tested anyway, however, 

and behaved normally in the BMS test. All such units that 

escape detection by the mine operator, MSHA, and our own 

inspections are tested to determine if they would have 

performed acceptably. If they had not been collected as part of 

our study, they could have been used in an emergency situation. 

OCENCO EBA 6.5 

None of the 30 deployed apparatus tested for breathing 

circuit tightness passed the leak test; 1 of the 3 new apparatus 

passed. Some units passed the test when their relief valves were 

capped, however, which implies backflow leakage through the 

valves. 

The Wilcoxon rank-sum tests [M=4; N=27] show that, in all 

performance measures, new units could not be distinguished 

from deployed units. 

No deployed or new units experienced CO2 breakthrough. 

The large range of average inhaled O2 level test averages is 

due to the difference in the apparatus O2 regulator flow rates, 

which ranged in this phase from 1.53 to 1.93 L/min ATPD. The 

O2 concentration in a breathing circuit will rise if the O2 supply 

rate is higher than the O2 consumption rate. 

In this phase, we found two units in which the orange 

cylinder bands had shifted, five units with cracks in their cases, 

and one unit with a blown-out case gasket. Any of these signs 

require the apparatus to be removed from service. In one unit 

with a case crack, the O2 flow was so high that the cylinder 

emptied in 59 min. In this instance, a shorter-than-normal 

duration would have been the only consequence. Another unit 

with case cracks had a demand valve which, when activated, 

stuck open. Turning off the cylinder valve closed the demand 

valve; this was done and the test was completed normally. Had 

this not been done, a severely curtailed duration would have 

resulted in this unit as well. The other units with disqualifying 

damage behaved normally. What remains of concern is the fact 

that damage requiring these units to be removed from service is 

very difficult to detect when the apparatus are dirty. The 

apparatus are cleaned after they are procured from the 

participating mines and only then does the damage reveal itself. 

The caution we issue is this: an apparatus caked with dirt 

cannot be properly inspected; dirt hides damage that may be 

critical. 

OCENCO M-20 

Of the nine deployed units tested for leak-tightness, two 

passed; of the three new units, two passed. 

Four deployed and all three of the new apparatus experienced 

average inhaled CO2 levels of 4% before exhaustion of the O2 

supply (table 5). In all but one instance, however, the depletion 

of the O2 supply was only 1 min or less away. One apparatus 

experienced CO2 breakthrough at minute 5 with a final duration 

of 18 min, at which time the average inhaled CO2 had reached 

7.5%. This unit also had a noticeable quantity of lithium 

hydroxide (LiOH) in the breathing bag and a lower-than-normal 

O2 flow rate, as evidenced by continuous demand valve use. 

The continuous use of the demand valve would have been of no 
12 

import to a user since a high work rate would also require 

continuous use of the demand valve. The LiOH dust in the 

breathing bag also would not have affected a user since none 

was found in the mouthpiece, but the higher CO2 values might 

have caused a higher ventilation rate in a user. It is likely that 

the LiOH in the breathing bag is evidence of chemical bed 

deterioration caused by physical impact from deployment (belt 

wear), which resulted in the higher CO2 values. Environmental 

simulation tests [Kyriazi 1996] showed similar results of LiOH 

escaping the chemical bed. NIOSH, MSHA, and Ocenco are 

currently investigating the problem. 

Table 5.—Ocenco M-20 CO2 breakthrough times, minutes 

Type of unit and 

test method 

CO2 breakthrough time 

Test 

duration 

Maximum 

CO2 

Deployed: BMS . . . . 17 18 4.4 

5 18 7.

17 17.5 4.5 

16 17 4.8 

New: BMS . . . . . . . . 19 19 4.1 

18 19 5.0 

18 19 4.5

5

 CO2 breakthrough for BMS - 4% average inhaled; for treadmill -

4% minimum inhaled.
 

The Wilcoxon rank-sum test [M=3; N=9] revealed that 

durations for deployed units were statistically significantly 

lower than those for new units. This could be caused by gas 

leakage 

from the cylinders or higher regulator flow rates in the deployed 

units. All of the apparatus had cylinder pressures in the 

acceptable (green) range. Since checking the cylinder gauge is 

one of the inspection criteria, apparatus having significantly low 

pressures would presumably be removed from service and 

would not present a serious problem. Also, since the durations 

of deployed units were only 2 min lower than those of new units 

(17 versus 19 min), this finding is not viewed with concern at 

present, but will be monitored for greater effects in future 

phases of this study. 

The Wilcoxon rank-sum test also showed that dry-bulb 

temperatures for new units may be statistically significantly 

higher than those for deployed units and that exhalation 

pressures for new units may be statistically significantly lower 

than those for deployed units. Dry-bulb temperatures of new 

units that are higher than those for deployed units may indicate 

lower reactivity of the chemical bed in deployed units. 

However, since CO2 levels were the same for new and deployed 

units, this finding is of no concern. Higher exhalation pressures 

for deployed units might indicate powdering of the chemical 

beds. However, since the pressures for new and deployed units 

were found to be so similar (see figure 11), this finding can be 

ignored and is attributable to the rank-sum test's inability to 

distinguish between large and small differences in values. 

Several M-20s had dirt migration into the cases, which 

indicates breaches in the case seals. One unit was missing its 

top bumper pad, which indicates rough usage. However, all of 

these apparatus performed normally. 

CONCLUSIONS
 

The results of this study suggest that the large majority of 

SCSRs that pass their inspection criteria can be relied upon to 

provide a safe level of life support capability for mine escape 

purposes. However, the mining environment seems to have 

caused some performance degradation in the CSE SR-100, 

Draeger OXY K-Plus, and Ocenco M-20. CSE has added a 

shake test to its inspection criteria in order to detect damage 

to the SR-100 chemical bed, which results in early CO2 

breakthrough. Several Draeger OXY K-Pluses were found with 

significant quantities of chemical in both the mouthpiece side of 

the breathing circuit and the breathing bag. As a consequence, 

Draeger developed a shake test to detect such damage. One 

Ocenco M-20 was found with chemical in the breathing bag; 

this unit also experienced early CO2 breakthrough and is 

presently under investigation. The MSA Life-Saver 60 was only 

r e c e n t l y 

introduced into the mines and has not been observed to suffer 

any hidden damage. The Ocenco EBA 6.5 is not belt-worn; it is 

thus spared from the greater degree of impact brought by belt 

wear. The greatest problem we have seen with it over the years 

is that, because the outer case is so tough, a severe impact may 

result in only a small crack that is not easily visible, especially 

if concealed by dirt. Such severe impact, however, may result 

in critical internal damage, which can compromise successful 

use of the device. Examples from past phases are damaged 

demand valves with high flow rates resulting in low durations; 

demand valves with cracked housing permitting in-leakage 

of ambient air; and damaged canisters resulting in LiOH spilling 

into the breathing circuit. Because of the importance of easy 

visual inspection, it is recommended that deployed apparatus 

of all types be cleaned of mine dirt for their regular inspections. 
13 

ACKNOWLEDGMENTS 

Without the cooperation of the coal mines and MSHA field 

offices, this study would not be possible. The following coal 

mines and MSHA field offices participated in the seventh phase 

of this study. 

Cooperating mine or MSHA office Location Mining company Mine name 

MSHA District 2:

 MSHA inspectors . . . . . . . . . . . . . . . . . . 

 Cyprus Emerald Resources Corp. . . . . . 

MSHA District 3:

 Anker West Virginia Mining Co. . . . . . . . 

 Wayne Processing, Inc. . . . . . . . . . . . . . 

 Coastal Coal/West Virginia LLC . . . . . . 

 Dana Mining Co., Inc. .............. 

 BJM Coal Co. . . . . . . . . . . . . . . . . . . . . 

MSHA District 4: 

 MSHA inspectors . . . . . . . . . . . . . . . . . . 

 Speed Mining, Inc. ................. 

 Quality Energy, Inc. . . . . . . . . . . . . . . . . 

 Ambush Mining Co., Inc. . . . . . . . . . . . . 

MSHA District 5:

 Falcon Coal Co. . . . . . . . . . . . . . . . . . . . 

MSHA District 6:

 Husky Coal Co., Inc. . . . . . . . . . . . . . . . 

MSHA District 7:

 Leeco, Inc. ....................... 

MSHA District 8:

 Black Beauty Underground, Inc. ...... 

 Old Ben Coal Co. . . . . . . . . . . . . . . . . . . 

 Peabody Coal Co. ................. 

 White County Coal Corp. ............ 

 Catlin Coal Co., Inc. . . . . . . . . . . . . . . . 

—

Emerald Mine No. 1 . . . . .

Stony River Mine . . . . . . .

Sentinel Mine . . . . . . . . . .

Whitetail Mine . . . . . . . . . .

Prime No. 1 Mine . . . . . . .

Mine 9A . . . . . . . . . . . . . .

—

Still Run No. 4 Mine .....

Mine No. 1 . . . . . . . . . . . .

Caretta No. 1 Mine . . . . . .

Mine No. 4 . . . . . . . . . . . .

Mine No. 7 . . . . . . . . . . . .

Mine No. 68 . . . . . . . . . . . 

Air Quality No. 1 Mine . . .

Zeigler No. 11 Mine . . . . .

Marissa Mine ..........

Pattiki Mine . . . . . . . . . . .

Riola Mine . . . . . . . . . . . .

 Ruff Creek, PA.

 Waynesburg, PA. 

 Mount Storm, WV.

 Philippi, WV.

 Kingwood, WV.

 Morgantown, WV.

 Summersville, WV. 

 Mount Hope, WV.

 Beckley, WV.

 Princeton, WV.

 Caretta, WV. 

 Grundy, VA. 

 Ashcamp, KY. 

 London, KY. 

 Evansville, IN.

 Courterville, IL.

 Marissa, IL.

 Henderson, KY.

 Catlin, IL. 

REFERENCES 

Hodgson, JL [1993]. Physiological costs and consequences of mine escape 

and rescue. University Park, PA: The Pennsylvania State University. U.S. 

Bureau of Mines contract Nos. J0145038 and J0345327. 

Kyriazi N [1996]. Performance comparison of second-generation oxygen 

self-rescuers. Pittsburgh, PA: U.S. Department of Energy, RI 9621. 

Kyriazi N, Shubilla JP [1992]. Self-contained self-rescuer field evaluation: 

results from 1982-90. Pittsburgh, PA: U.S. Department of the Interior, Bureau 

of Mines, RI 9401. 

Kyriazi N, Shubilla JP [1994]. Self-contained self-rescuer field evaluation: 

fourth-phase results. Pittsburgh, PA: U.S. Department of the Interior, Bureau 

of Mines, RI 9499. 

Kyriazi N, Shubilla JP [1996]. Self-contained self-rescuer field evaluation: 

fifth-phase results. Pittsburgh, PA: U.S. Department of Energy, RI 9635. 

Kyriazi N, Shubilla JP [2000]. Self-contained self-rescuer field evaluation: 

sixth-phase results. 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) 

Publication No. 2000-128, IC 9451. 

Kyriazi N, Kovac JG, Shubilla JP, Duerr WH, Kravitz J [1986]. Selfcontained self-rescuer field evaluation: first-year results of 5-year study. 

Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9051. 
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