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
This document is the public domain and may be freely copied or reprinted.

Disclaimer: Mention of any company or product does not constitute endorsement by NIOSH.

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DHHS (NIOSH) Publication No. 2002-127
CONTENTS

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 and John P. Shubilla2

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.

1

Biomedical engineer.

2

Engineering technician.

National Personal Protective Technology Laboratory, National Institute for Occupational Safety and Health, Pittsburgh, PA.
2

Figure 1.—Breathing and metabolic simulator.

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

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.

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 . . . . . . . . . 2 10

 Total . . . . . . . . . . . . . . — 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
3

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

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

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

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

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.

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. 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. The probability of T falling

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

mean.

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 . . 89 (1

) (1) (1) 

 Exhalation . . . . . . . . . . . . . . . . . . . L/min . . 71 (1

) (1) (1) 1

Not measured.

Table 3.—Wilcoxon rank-sum test results

Apparatus Duration Average

inhaled CO2

Average

inhaled O2

Wet-bulb

temperature

Dry-bulb

temperature

Inhalation

pressure

Exhalation

pressure

Range T Range T Range T Range T Range T Range T 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).
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. 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.

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 60 4.4

56 58 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 52 4.3

49 49 4.6

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

minimum inhaled.

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

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

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.

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 7.5

17 17.5 4.5

16 17 4.8

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

18 19 5.0

18 19 4.5

 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

recently

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 . . . . . . . . . . . . . . . . . . — Ruff Creek, PA.

 Cyprus Emerald Resources Corp. . . . . . Emerald Mine No. 1 . . . . . Waynesburg, PA.

MSHA District 3:

 Anker West Virginia Mining Co. . . . . . . . Stony River Mine . . . . . . . Mount Storm, WV.

 Wayne Processing, Inc. . . . . . . . . . . . . . Sentinel Mine . . . . . . . . . . Philippi, WV.

 Coastal Coal/West Virginia LLC . . . . . . Whitetail Mine . . . . . . . . . . Kingwood, WV.

 Dana Mining Co., Inc. . . . . . . . . . . . . . . Prime No. 1 Mine . . . . . . . Morgantown, WV.

 BJM Coal Co. . . . . . . . . . . . . . . . . . . . . Mine 9A . . . . . . . . . . . . . . Summersville, WV.

MSHA District 4:

 MSHA inspectors . . . . . . . . . . . . . . . . . . — Mount Hope, WV.

 Speed Mining, Inc. . . . . . . . . . . . . . . . . . Still Run No. 4 Mine . . . . . Beckley, WV.

 Quality Energy, Inc. . . . . . . . . . . . . . . . . Mine No. 1 . . . . . . . . . . . . Princeton, WV.

 Ambush Mining Co., Inc. . . . . . . . . . . . . Caretta No. 1 Mine . . . . . . Caretta, WV.

MSHA District 5:

 Falcon Coal Co. . . . . . . . . . . . . . . . . . . . Mine No. 4 . . . . . . . . . . . . Grundy, VA.

MSHA District 6:

 Husky Coal Co., Inc. . . . . . . . . . . . . . . . Mine No. 7 . . . . . . . . . . . . Ashcamp, KY.

MSHA District 7:

 Leeco, Inc. . . . . . . . . . . . . . . . . . . . . . . . Mine No. 68 . . . . . . . . . . . London, KY.

MSHA District 8:

 Black Beauty Underground, Inc. . . . . . . Air Quality No. 1 Mine . . . Evansville, IN.

 Old Ben Coal Co. . . . . . . . . . . . . . . . . . . Zeigler No. 11 Mine . . . . . Courterville, IL.

 Peabody Coal Co. . . . . . . . . . . . . . . . . . Marissa Mine . . . . . . . . . . Marissa, IL.

 White County Coal Corp. . . . . . . . . . . . . Pattiki Mine . . . . . . . . . . . Henderson, KY.

 Catlin Coal Co., Inc. . . . . . . . . . . . . . . . Riola Mine . . . . . . . . . . . . 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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