Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Self-Contained Self-Rescuer

Long Term Field Evaluation

Combined Eighth and Ninth

Phase Results

RI 9671

REPORT OF INVESTIGATIONS /2006
Report of Investigations

Self-Contained Self-Rescuer Long Term 

Field Evaluation: Combined Eighth and 

Ninth Phase Results

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

October 2006
Self-Contained Self-Rescuer Long Term Field Evaluation iii

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

Disclaimer

Mention of any company or product does not constitute endorsement by the National Institute for 

Occupational Safety and Health (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.

Ordering Information

To receive documents or other information about occupational safety and health topics, contact 

NIOSH at

NIOSH—Publications Dissemination

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Telephone: 1–800–35–NIOSH (1–800–356–4674)

Fax: 513–533–8573

E-mail: pubstaft@cdc.gov

or visit the NIOSH Web site at www.cdc.gov/niosh

DHHS (NIOSH) Publication Number 2007–103

October 2006

Safer • Healthier • PeopleTM
iv Self-Contained Self-Rescuer Long Term Field Evaluation

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Evaluation Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Results and Discussion ........................................................ 6

CSE SR-100 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Draeger OXY K-Plus Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

MSA Life-Saver 60 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

OCENCO EBA 6.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

OCENCO M-20 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Long Term Field Evaluation Phase 8 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Long Term Field Evaluation Phase 9 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Redesigned Long Term Field Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Appendix 1—Certified Product Investigation Program 

(CPIP) Investigations Initiated from LTFE 8 and 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Appendix 2—Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Appendix 3—ASMD Test Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Figures

Figure 1. Breathing and Metabolic Simulator ..................................... 3

Figure 2. Treadmill Testing .................................................... 3

Figure 3. Uncased and Cased CSE SR-100 Self-Rescuer ............................. 4

Figure 4. Cased and Uncased Draeger OXY K-Plus Self-Recuer ...................... 4

Figure 5. Cased and Uncased MSA Life-Saver 60 Self-Rescuer ....................... 4

Figure 6. Cased and Uncased OCENCO EBA 6.5 Self-Rescuer ....................... 4

Figure 7. Partially Uncased and Uncased OCENCO M-20 Self-Rescuer ............... 5

Figure 8. Depletion Time for All Models Tested ................................... 6

Figure 9. Dented Draeger OXY K-Plus Belt-Clip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 10. Internal damage on Draeger OXY K-Plus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Tables

Table 1. SCSRs Collected for Evaluation .......................................... 3

Table 2. Test Parameters for Units with Testing Terminated Prior to O2Depletion . . . . . . . . 6
Self-Contained Self-Rescuer Long Term Field Evaluation v

Table 3. BMS and Treadmil Metabolic Parameters .................................. 8

Table 4. Wilcoxon Rank-Sum Test Results......................................... 10,11

Table 5. Lab Inspection Results for CSE SR-100 .................................... 12,13

Table 6. Lab Inspection Results for Draeger OXY K-Plus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 7. Lab Inspection Results for MSA Life-Saver 60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 8. Lab Inspection Results for OCENCO EBA 6.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 9. Lab Inspection Results for OCENCO M-20 - Phase 9 . . . . . . . . . . . . . . . . . . . . . . . . 25

Contents
vi Self-Contained Self-Rescuer Long Term Field Evaluation

SELF-CONTAINED SELF-RESCUER LONG TERM FIELD EVALUATION

COMBINED EIGHTH AND NINTH PHASE RESULTS

Abstract

The National Institute for Occupational Safety and Health (NIOSH) National Personal Protective Technology Laboratory (NPPTL) and the Mine Safety and Health Administration (MSHA) 

conduct a Long Term Field Evaluation (LTFE) program to evaluate deployed self-contained selfrescuers (SCSRs). The objective of the program is to evaluate how well SCSRs endure the underground coal mining environment with regard to both physical damage and aging when they are 

deployed in accordance with Federal regulations (30 CFR 75.1714). This report presents findings 

of the combined eighth and ninth phases of the LTFE. For these phases, over four hundred SCSRs 

were evaluated. The units tested include the CSE SR-100, Draeger Oxy K-Plus, MSA Life-saver 60, 

and the OCENCO EBA 6.5. The OCENCO M-20 was evaluated only in Phase 9. Testing was performed between December 2000 and April 2004. Results of the evaluation indicate that all SCSRs 

experience some performance degradation due to the mining environment. Observed degradation varies from elevated levels of carbon dioxide, high breathing resistance, and reduced capacity. 

Mechanical degradation to the SCSR components included breathing hoses, chemical beds, outer 

cases and seals. The LTFE tests discussed in this report are different from tests performed for SCSR 

certification to the requirements of 42 Code of Federal Regulations, Part 84 (42 CFR, Part 84). LTFE 

tests reported here are conducted to an end point, oxygen depletion, to enable comparison of the 

duration of new and deployed SCSRs. The method for obtaining deployed SCSRs for this evaluation was not a random selection from the deployed population of SCSRs. Although the results of 

these tests are useful for observing performance of the tested SCSRs, they are not representative of 

all deployed SCSRs. A new evaluation protocol, with revised sampling strategies, test methods, and 

reporting procedures, is currently being designed to enhance the generalizability of the results. This 

program will be implemented following completion of Phase 10 of the current LTFE protocol.
Self-Contained Self-Rescuer Long Term Field Evaluation 1

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 hour, 

as approved according to the requirements 

found at Title 42, Code of Federal Regulations, 

Part 84 (42 CFR, Part 84). The SCSRs are sealed 

to protect them from the underground mining 

environment. The sealed case that protects the 

apparatus from environmental and physical 

damage also makes it difficult to inspect. Unlike 

general industry open-circuit, self-contained 

breathing apparatus, no functional assessment 

can be made prior to actual use. For these reasons, the National Institute for Occupational 

Safety and Health (NIOSH) National Personal 

Protective Technology Laboratory (NPPTL) in 

cooperation with the Mine Safety and Health 

Administration (MSHA) conducts an ongoing, 

long term field evaluation of SCSRs deployed in 

underground coal mines. NPPTL locates mines 

willing to participate in the study and acquires 

deployed SCSRs by supplying new replacement 

units in cooperation with MSHA. The NPPTL 

then tests the deployed SCSRs. Approximately 

90% of tests are performed using a breathing 

and metabolic simulator (BMS), while 10% 

are evaluated by human test subjects with 

MSHA inspectors among those serving as human subjects. The objective of this program is 

to evaluate how well SCSRs endure the underground coal mining environment with regard 

to both physical damage and aging. This report 

presents results from Phase 8 and Phase 9 testing conducted between December 2000 and 

April 2004. Previous reports describe Phases 1 

through 7 of the Long Term Field Evaluation 

(LTFE) program [Kyriazi et al. 1986; Kyriazi 

and Shubilla 1992, 1994, 1996, 2000, 2002].

Mines must conduct regular inspections of 

deployed units to ensure SCSR readiness. The 

criteria for these inspections are established by 

the manufacturers and include damage assessments of specific components by either visual 

inspection or non-destructive testing. Among 

the visual inspection criteria are evaluating the 

use indicators or gauges provided on the unit, 

checking the service life date, and visually assessing physical indications of wear. Users 

must comply with the manufacturer’s specified 

conditions of use. SCSRs failing inspection or 

not complying with the conditions of use no 

longer meet the NIOSH/MSHA approval and 

should be removed from service. 

The tests performed as part of the LTFE are 

focused on detecting any changes in deployed 

respirators. NPPTL tests to endpoints and 

under conditions to facilitate performance 

comparison between new and deployed units. 

These tests are different from the tests used in 

respirator certification. The LTFE tests are consistent with SCSRs performing at a constant 

work rate in an underground escape scenario. 

The test data from LTFE testing should not be 

used to predict actual respirator performance 

for a miner in an emergency where work rates 

can vary based on escape route conditions, 

miner fitness level, etc. As stated earlier, many 

tests are conducted using a BMS instead of 

human test subjects. The machine provides a 

reproducible measure to enable comparison 

of new and deployed units. Although certification tests using human subjects and simulator testing using the BMS can produce similar 

results, they are different tests, and the data 

Introduction
2 Self-Contained Self-Rescuer Long Term Field Evaluation

reported from BMS testing cannot be considered equivalent to certification tests using human subjects.

The suspected problems and nonconformities 

identified in the LTFE program are reported for 

investigation under the Certified Product Investigation Program (CPIP). These investigations 

and their outcomes are reported in Appendix 

1. However, the method for obtaining deployed 

SCSRs for this evaluation was not a random 

selection from the deployed population of SCSRs. Although the results of these tests are useful 

for observing performance of the tested SCSRs, 

they are not representative of all deployed SCSRs. Redesign of the LTFE to address sampling 

strategies, test methods, and reporting procedures is under development by NIOSH NPPTL 

and will be implemented following peer review, 

stakeholder input, and completion of Phase 10 

testing in the current LTFE program.

Introduction
Self-Contained Self-Rescuer Long Term Field Evaluation 3

Over 400 SCSRs were tested in the eighth and 

ninth phases of the study conducted December 2000 – April 2004. Ninety percent of the 

apparatus were tested on a BMS (Figure 1) 

and 10% were tested using human subjects on 

a treadmill (Figure 2). MSHA provides human 

test subjects from its Mine Emergency Unit for 

treadmill testing.

MSHA assisted in selecting the participating 

mines from mines indicating a willingness to 

participate in the LTFE program by considering the type of mining operation, coal bed 

height, and SCSR deployment mode, so as 

to represent a wide range of conditions that 

could impact SCSR performance. NIOSH 

staff, accompanied by MSHA inspectors, applies the manufacturers’ inspection criteria on 

units currently deployed at each mine during 

an on-site visit to acquire sample SCSRs for 

testing. New units are exchanged for deployed 

units judged to meet the manufacturer’s criteria, and the mines are advised to remove 

rejected units from service. Mines selected 

for participation in Phase 8 and Phase 9 are 

identified in the Acknowledgements. Deployment modes included permanent storage on 

the mine floor, storage on a man-trip or mining machine, daily carry-and-store, and beltworn. The number collected for each phase is 

indicated in Table 1.

Table 1. SCSRs Collected for Evaluation

Apparatus

Number 

Collected 

Phase 8

Number 

Collected 

Phase 9

CSE SR-100 90 98

Draeger OXY 

K-Plus

24 20

MSA Life-Saver 60 35 20

OCENCO EBA 6.5 80 57

OCENCO M-20 0* 20

Total 229 215

*

Not included in Phase 8 because new models were not 

available

Evaluation Procedure

Figure 1. Breathing and Metabolic Simulator

Figure 2. Treadmill Testing
4 Self-Contained Self-Rescuer Long Term Field Evaluation

Units were prescreened by visual inspection in 

accordance with the manufacturer’s inspection 

criteria during the collection procedure to reject units with evidence of potential damage. 

Evaluated SCSRs were manufactured by CSE 

Corp., Drägerwerk AG (Draeger), Mine Safety 

Appliances Co., Inc. (MSA), and OCENCO, 

Inc. Units were sampled according to estimated 

distribution of the various models and are 

shown in Figures 3 through 7. By the end of 

Phase 9, the MSA Life-Saver 60 was no longer 

being manufactured or distributed. The devices evaluated represent all NIOSH/MSHA 

certified SCSRs available and in use in United 

States coal mines. The devices vary in size and 

weight. Some can be worn on the miners’ work 

belts, others cannot.

Figure 3. Uncased and Cased CSE SR-100 

Self-rescuer

Figure 4. Cased and Uncased Draeger OXY 

K-Plus Self-rescuer

Figure 5. Cased and Uncased MSA Life-Saver 

60 Self-rescuer

Figure 6. Cased and Uncased Ocenco EBA 6.5 

Self-rescuer 

Evaluation Procedure
Self-Contained Self-Rescuer Long Term Field Evaluation 5

Figure 7. Partially Uncased and Uncased 

Ocenco M-20 Self-rescuer 

Evaluation Procedure
6 Self-Contained Self-Rescuer Long Term Field Evaluation

The depletion times for the deployed and new units are shown in Figures 8a and 8b for Phases 8 

and 9 respectively.

Figure 8a. Depletion Time for All Models Tested–Phase 8

Figure 8b. Depletion Time for All Models Tested–Phase 9

Results and Discussion

Figure 8. Depletion Time for All Models Tested
Self-Contained Self-Rescuer Long Term Field Evaluation 7

Table 2 summarizes the number of units with 

testing terminated for reasons other than oxygen depletion. Both LTFE Phase 8 and Phase 

9 results are indicated in the table. The table 

includes units demonstrating decreased oxygen (O2) levels, increased carbon dioxide 

(CO2) levels, high breathing resistance (pressure), and coughing.

In the following discussion, results for each 

SCSR model are described separately. The time 

to depletion for deployed versus new units is 

compared by phase for all units. As stated earlier, 

some units failed visual inspection in the laboratory. A list of SCSRs failing inspection, and the 

reasons for failure, is included. For each type of 

unit and for each phase, the proportion of SCSRs 

failing laboratory inspection is reported. 

The minute-average values of the monitored 

stressors were averaged over the entire test duration, and are presented graphically for each 

apparatus by stressor in Appendix 2 (Figures 

A2-1 through A2-9). The values for new and 

deployed units tested on the BMS can be compared. To some extent, these values may also 

be compared with those for deployed units 

tested on human subjects on a treadmill; however, human subjects may differ from each 

other and from the BMS in terms of CO2 production rate, ventilation rate, and respiratory 

frequency. These parameters affect apparatus 

duration as well as all of the monitored variables. Treadmill tests cannot be considered 

equivalent to the BMS tests, even though the 

O2 consumption rate is the same. 

Inspection Procedures

All units were inspected using the manufacturers’ inspection criteria after being cleaned. 

If an induced noise test was required, the test 

was performed to the manufacturer’s specifications. Despite having passed the inspection 

during collection, some collected units were 

judged to have failed the manufacturer’s inspection criteria once received in the laboratory. In other words, these units should have been 

removed from service, and not been available 

for the LTFE tests. Failure could be attributed 

to differences in judgment as to the compliance with inspection criteria. This reflects the 

difficulty of inspecting units deployed in the 

underground coal mine environment. Units 

can become encrusted with dirt making a 

thorough inspection difficult. The test results 

and data analysis, therefore, include all units 

tested whether they passed subsequent laboratory visual inspection or not. Units that failed 

laboratory inspection are noted in the results.

Breathing and Metabolic 

Simulator (BMS) and 

Treadmill Testing

The BMS test consists of the average metabolic 

work rate exhibited by the 50th-percentile miner weighing 87 kg while performing Man-test 

4 for one hour, as described in 42 CFR, Part 

84. Although the average work rate is the same, 

LTFE testing is not equivalent to certification 

testing. Certification testing imposes high and 

Table 2. Test Parameters for Units with Testing Terminated Prior to O2 Depletion

Results and Discussion
8 Self-Contained Self-Rescuer Long Term Field Evaluation

low work rates that the average work rate used 

in the LTFE does not. Also, the stressor levels are continuously monitored in the LTFE, 

whereas they are sampled only between work 

activities in certification testing. In addition, 

LTFE testing continues until the apparatus is 

empty or stressor levels exceed allowable parameters, whereas testing during certification 

ends at the rated duration, even if the capacity 

of the apparatus exceeds it. 

In the LTFE treadmill testing, the human subjects walked at the speed and grade that elicited an O2 consumption rate of 1.35 L/min. The 

carbon dioxide (CO2) production rate, ventilation rate, and respiratory frequency varied in 

the test subjects. The metabolic parameters for 

both BMS and treadmill testing are given in 

Table 3.

the BMS were terminated upon one of three 

endpoints: exhaustion of the O2 supply as indicated by inhalation pressures reaching -200 

mm H2O, coinciding with an empty breathing bag; average inhaled CO2 levels exceeding 

10%; or O2 levels below 15%. 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 resistances (pressures) 

or temperatures.

The Wilcoxon rank-sum test was performed for 

each monitored stressor to determine whether 

deployed units behaved differently from new 

units. The test evaluates 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 

Table 3. BMS and Treadmill Metabolic Parameters

Metabolic workload BMS Treadmill

O2 consumption rate, L/min. 1.35 1.35

CO2 production rate, L/min. 1.15 *

Ventilation rate, L/min. 30.0 *

Tidal volume, L/breath 1.68 *

Respiratory frequency, breaths/min. 17.9 *

Peak respiratory flow rate:

Inhalation, L/min. 89 *

Exhalation, L/min. 71 *

*Pace of treadmill test is set to maintain oxygen consumption at the stated rate.

In both BMS and treadmill testing, the monitored stressors included inhaled levels of CO2

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

temperatures, and peak inhalation and exhalation breathing resistances (pressures). Tests on 

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 sufficient 

evidence does not exist at the specified probability level (α = .05, two-sided) to conclude 

Results and Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 9

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. A limitation of the Wilcoxon rank-sum test is that it 

does not distinguish between large and small 

differences in values. The results of the α = .05, 

two-sided, Wilcoxon rank-sum tests are presented in Table 4a for the units tested in Phase 

8 and Table 4b for the units tested in Phase 9. 

The probability of T falling outside the given 

range is .05 if the populations have the same 

mean. Results where T falls outside the range 

are highlighted.

Results and Discussion
10 Self-Contained Self-Rescuer Long Term Field Evaluation Table 4. Wilcoxon Rank-Sum Test Results Table 4a. Wilcoxon Rank-Sum Test Results – Phase 8 Duration Average Inhaled CO2 Average Inhaled O2 Wet-bulb Temp Dry-bulb Temp Inhalation Pressure Exhalation Pressure Apparatus Range T Range T Range T Range T Range T Range T Range T SR-100 45-120 60 45-120 57 45-120 103 43-117 131 45-120 133 45-120 144 45-120 116 OXY K-Plus 26-82 67 25-79 53 26-82 70 26-82 70 26-82 56 26-82 61 26-82 48 Life-Saver 60 12-48 50 12-48 28 12-48 28 12-45 28 12-48 26 12-48 52 12-48 30 EBA 6.5 28-88 50 28-88 24 28-88 72 28-88 60 28-88 70 28-88 50 28-88 22 Note that the numbers in the table are rank numbers and do not represent test values T=Sum of the ranks of the smaller sample (new units)

Results and Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 11 Table 4. Wilcoxon Rank-Sum Test Results Table 4b. Wilcoxon Rank-Sum Test Results – Phase 9 Duration Average Inhaled CO2 Average Inhaled O2 Wet-bulb Temp Dry-bulb Temp Inhalation Pressure Exhalation Pressure Apparatus Range T Range T Range T Range T Range T Range T Range T SR-100 99-205 126 101-211 121 99-205 198 99-205 231 99-205 236 99-205 132 99-205 142 OXY K-Plus 24-76 58 24-76 67 24-76 84 24-72 65 24-76 49 24-76 33 24-76 32 Life-Saver 60 13-53 60 13-53 42 13-53 42 13-53 48 13-53 46 13-53 7 13-53 39 EBA 6.5 30-94 56 30-94 26 30-94 76 30-94 52 30-94 61 30-94 70 30-94 23 M-20 13-53 52 23-69 68 13-53 46 13-53 32 13-53 42 13-53 39 13-53 37 Note that the numbers in the table are rank numbers and do not represent test values T=Sum of the ranks of the smaller sample (new units)

Results and Discussion
12 Self-Contained Self-Rescuer Long Term Field Evaluation

Induced Noise Test

CSE developed a test to identify apparatus that 

have sustained internal damage, based on a correlation between loose particles in the chemical bed and CO2 breakthrough during the last 

rest interval of a 1-hour Man Test #4. This 

was established by testing SR-100s on the CSE 

breathing simulator performing NIOSH variable-work rate certification tests. The Acoustic 

Solids Movement Detector (ASMD) analyzes 

the noise induced in the unit by shaking it in a 

controlled manner. The noise produced by the 

SCSR when shaken is used as an indicator of 

shock and vibration damage incurred by the 

chemical bed within the SCSR. In the field, this 

assessment is made using a hand-held instrument provided by CSE. A laboratory version 

of the ASMD test involves rotating the SR-100 

in an anechoic chamber to measure the noise 

levels in decibels (dB). Various frequency 

ranges are weighted differently and result in a 

composite dB rating for each apparatus. A unit 

with a composite rating of higher than 60 dB 

fails the test. NIOSH performs the laboratory 

version of the ASMD test as part of the LTFE 

inspection. Excessive noise as evaluated by either of the test instruments is an indication of 

chemical-bed damage that may adversely affect 

the performance of the SCSR. SCSRs failing 

the ASMD test must be removed from service. 

The ASMD test and average inhaled CO2 levels 

on CSE units on a BMS performing a constant 

work rate test are presented in Figures A3-1a 

and A3-1b. 

Units failing manufacturer’s inspection criteria at the laboratory are shown in Tables 5a 

and 5b. The failure rate in Phase 8 was 19% of 

the 90 units collected, and for Phase 9 it was 

30% of the 98 units collected. Those failures 

highlighted in orange were due to ASMD test 

results exceeding the 60 dB limit to remain in 

service (test result > 60 dB). 

Table 5. Lab Inspection Results for CSE 

SR-100

Table 5a. Lab Inspection Results for CSE 

SR-100–Phase 8

SN Failure

33269 Chunk of orange case missing

34269 70 dB

40075 Deeply cracked orange case

42855 Cracks and holes in orange case

49088 Hole in orange case

51042 114 dB

53058 Cracks and holes in orange case

54954 Cracks and holes in orange case

57901 Bottom moisture indicator cracked

57942 77 dB

58989 Bottom moisture indicator cracked

59136 72 dB

61221 Cracks and holes in orange case

61303 Holes in orange case

68490 101 dB

69648 Bottom moisture indicator cracked

71768 Bottom moisture indicator white; seal 

chewed

CSE SR-100 Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 13

Table 5b. Lab Inspection Results for CSE SR-100–Phase 9

SN Failure

34167 Dent in bottom case seal

34407

Approximately 15% of orange

case missing

39017 68 dB

40068 Large gash in orange case showing through metal

45233 78 dB

46971 Pieces of orange case missing

46994 65 dB

47009 82 dB

50138 88 dB

51152 Significant cracks and pieces missing from orange case

51297 62 dB

51430 62 dB

52048 Big dent in top corner; big crack on side

52366 95 dB

52480 61 dB

57288 109 dB

57430 62 dB

57636 91 dB

58929 Severely cracked orange case with pieces missing

61281 Severely cracked orange case

63804 71 dB

68375 80 dB; dented bottom seal and damaged gasket

67414 Cracked moisture lens

75576 Huge cracks in orange case with pieces missing

78338 61 dB

79086 63 dB

85247 80 dB

85285 62 dB

88252 74 dB

88288 117 dB

89282 87 dB

90544 67 dB

CSE SR-100 Discussion
14 Self-Contained Self-Rescuer Long Term Field Evaluation

BMS and Treadmill Testing

The durations were comparable for both new 

and deployed units in both phases as shown in 

Figures 8a and 8b. In Phase 8, nine units had 

little or no starter oxygen, requiring a manual 

start before beginning or shortly after beginning the test. In Phase 9, 15 units had little or 

no starter oxygen. Manual starts consist of exhaling into the apparatus until the breathing 

bag is full (3 to 6 breaths). Since exhaled breath 

contains sub-ambient levels of O2 (approximately 17%) the inhalation levels of O2 started 

at that point, declined to below 15% within a 

couple of minutes, and reached a minimum at 

approximately 12% before rising.

In all human subject tests, the users coughed 

when donning the apparatus. This was thought 

primarily to be due to inhalation of loose corn 

starch particles. The manufacturer uses corn 

starch in the breathing hose to absorb saliva. 

The corn starch prevents saliva from reaching 

the KO2 bed where it would speed up the chemical reaction and waste O2. After noticing the 

corn starch in the breathing hoses, an attempt 

was made to shake out the loose particles before testing the units. This resulted in dislodging small pieces of metal (end-cuttings from 

the wire-mesh heat-exchanger) from the hoses. 

(The manufacturer has added a step during 

manufacture to blow out the loose metal cuttings.) The donning procedure was changed and 

the human subjects were instructed to dampen 

the loose particles by exhaling repeatedly into 

the units. When O2 fell below 15%, the user was 

instructed to activate the starter O2. This sometimes caused a fresh series of coughs, including 

one in which the test subject complained after 

the test that his throat burned. In some tests, instead of immediately beginning to walk on the 

treadmill, the test subjects stood still until the 

O2 levels stabilized, usually at about 16%. However, as soon as the test subjects began walking 

at their target speed, the O2 levels quickly fell 

below 15% and the starter O2 was activated.

Most tests were terminated when their O2 supply was expended. In phase 9, four units were 

terminated for high CO2 levels, four for low O2

levels, two for high breathing pressures, and 

one for coughing. Of the four tests terminated 

for low O2 levels, three of the apparatus should 

have failed inspection for various reasons. 

One, which was terminated at 73 minutes simultaneously with an empty breathing bag, 

had ASMD test results exceeding the criteria 

to remain in service (test result = 109 dB). Another, terminating at 22 minutes, also had an 

ASMD test result exceeding the criteria to remain in service (test result = 88 dB) plus large 

cracks in the orange jacket with pieces missing, and a severe side dent. It also had insufficient starter O2. The third unit, which ran for 

only one minute before dropping below 15% 

O2, had a badly dented metal case and a severe 

dent in the lower case seal, and contained no 

starter O2. The low O2 levels in these three apparatus can probably be attributed to chemical 

bed degradation. The fourth unit passed all inspection criteria, but had a punctured breathing hose and no starter O2, neither of which 

could have been detected through inspection. 

It was terminated at 69 minutes. The low O2

levels in this apparatus can be attributed to 

the in-leakage of ambient air through the hose 

puncture.

The test that was stopped for coughing was 

terminated after three minutes. This apparatus had severe cracks in its orange jacket with 

pieces missing, requiring it to be taped together. Upon opening the case, the findings exhibited coal dust migration through the case seals, 

and the breathing hose was punctured. The 

test subject coughed upon initial donning, but 

continued testing. However, after the starter 

O2 was activated, which occurred with a popping sound, the coughing became worse, and 

the test subject, an MSHA inspector, declined 

to continue.

Results and Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 15

Increased CO2

In Phase 8, of the 87 deployed apparatus tested 

on the BMS, 25 experienced CO2 levels in excess of 4% before 60 minutes: 64 experienced 

CO2 in excess of 4% before expenditure of the 

O2 supply. Four of eight new units also experienced breakthrough; three before 60 minutes. 

The response to high inhaled levels of CO2 will 

be increased ventilation rates in most users, approximately doubling with 4% CO2. Increased 

ventilation rates will result in higher breathing 

pressures for the user. Breathing resistance in 

the SR-100 increases rapidly toward end-ofservice-life, even in some new apparatus, and 

elevated CO2 levels even could result in higher 

breathing resistance than normal.

In Phase 9, all four tests terminated for high 

CO2 levels (10% CO2 in the two BMS tests, and 

4% CO2 in the two treadmill tests) had noise induced sound level test dB levels higher than 60 

and should have been removed from service. 

Breathing Resistance

In phase 8, four BMS tests and three treadmill 

tests of deployed units were terminated because of high breathing pressures (exceeding 

the + 715 mm H2O range of the pressure transducer in the BMS tests, or at the discretion of 

the human subject in the treadmill tests, ranging from + 230 to 500 mm H2O). One BMS 

test of a new unit was also terminated for high 

breathing pressures. The breathing pressures 

in most tests did not reach high levels until approximately 50 minutes. However, one treadmill test did have high pressures early and was 

terminated at 16 minutes. Disassembly at CSE 

revealed a layer of fused potassium superoxide (KO2) at the bottom of the chemical bed, 

possibly due to water in-leakage into the case 

bottom, even though the color indicator was 

blue (passing inspection) at the time of testing. It may be possible for an indicator to turn 

pink if water or humidity leaks in through a seal 

breach, and then revert back to blue after drying out. The damage has been done, however, 

showing the importance of daily inspections. 

Most of the other tests were terminated due to 

oxygen depletion or because of high CO2 (Table 

2). One test ended due to low O2 levels.

In Phase 9, of the two tests terminated for 

high breathing pressures, the BMS test was 

terminated when the pressure reached -600 

mm H2O at 55 minutes. The treadmill test 

was terminated at the request of the test subject when pressures reached + 300 mm H2O

at 51 minutes. A BMS test of a new unit was 

also terminated for high breathing pressures 

at 60 minutes. Thirty-four deployed apparatus 

reached +200 mm H2O, while 25 reached -300 

mm H2O. These pressures were the limits of 

tolerance for 80% of test subjects in a study 

contracted by the Bureau of Mines (Hodgson, 

1993). In 10 units, the inhalation breathing 

pressure limit was exceeded before 60 minutes, 

while in 16 units, the exhalation limit was exceeded before 60 minutes

Other Observations

In one case in Phase 9, the user said his throat 

burned, and that it was more than corn starch, 

based on his previous experience. Since KO2

was found in another SR-100, it is possible that 

it was KO2 in this apparatus, also. The apparatus in which KO2 was determined to be present had been taken to CSE and disassembled. 

It was found that the canister had been dented, 

deforming the seal that contains the chemical 

bed. This apparatus had passed all its inspection criteria. There was no way for a user to 

have detected the damage to the metal canister 

underneath the orange plastic case.

In Phase 8, nine units had breathing hoses with 

severe creases with the hose walls stuck to each 

other. A careful effort to open the flow path 

Results and Discussion
16 Self-Contained Self-Rescuer Long Term Field Evaluation

was required. In two instances, simply extending the hose resulted in tearing the hose. Even 

a conscientious effort in two more instances to 

open the flow path resulted in tearing. Similar conditions were observed in Phase 9, where 

breathing hoses of eighteen units were severely 

creased with the hose walls stuck to each other. 

A careful effort to open the flow path was required. In two cases the hoses tore when attempting to open the flow path. Thereafter, the 

hoses were left stuck and partially occluded. 

The manufacturer has determined that this 

degradation is caused by heat exposure.

In both Phase 8 and Phase 9, the breathing hose 

was either punctured or slit in eight units and 

nine units respectively, apparently from being 

pressed against sharp internal components. 

Such holes would permit toxic gases and N2 to 

enter the breathing circuit in emergency use, 

compromising the effectiveness of the apparatus. To correct this problem, the manufacturer 

has changed its packing procedures.

In Phase 8, at least 10 units had evidence of 

dirt and/or past water leakage into the case. 

The color indicators were blue in all units. In 

spite of the apparent breach of the case seals, 

all apparatus performed normally. In Phase 9, 

14 units exhibited evidence of dirt and/or water leakage into the case. The color indicators 

were blue in all units. In Phase 9, ten apparatus had some degree of performance degradation.

In Phase 8, one apparatus leaked badly from 

the relief valve. Another unit had a breathing 

bag with chemical deposits of unknown material, and the bag was stuck to itself in several 

places. These peculiarities did not significantly 

affect the performance of the apparatus. Subsequent internal examination of this unit with 

the assistance of the manufacturer revealed 

signs of electrical arcing in the area where the 

bag was stuck together. The chemical deposits 

were deemed by the manufacturer to also be 

related to the arcing.

In Phase 9, the lids on five apparatus were difficult to open to varying degrees. On one unit, 

the thumb-strap used to open the case broke; 

in another unit, the breathing bag was stuck to 

itself and had to be manually unstuck. The relief valve cap was warped on one unit and fell 

off during the test, with no apparent effect on 

performance. One human subject said that he 

felt light-headed immediately after activating 

the starter O2, although he continued with the 

test until completion.

Wilcoxon Rank-Sum Test

In earlier reports (Phases 6 and 7), the Wilcoxon rank-sum test for average inhaled CO2

showed that the new units had significantly 

lower values than deployed units. Using only 

the three new units from the last phase for 

comparison with the deployed units from 

the Eighth Phase, the same findings were observed: the deployed units had higher CO2 values. However, the group of new units was expanded with two recently manufactured units 

(January 2001), which also had higher CO2

levels. This put them more in line with the 

deployed units and eliminated the distinction 

between new and deployed units with regard 

to CO2 levels. To further explore this situation, 

two more new units manufactured within a 

month of the two newer units already evaluated were tested. As in previous results, high CO2

levels were obtained. An apparatus manufactured in January of 2002 was then tested. This 

apparatus showed low levels of CO2. Given 

such variability of CO2 levels in new units, the 

higher CO2 levels in deployed units cannot be 

attributed solely to bed degradation caused by 

rough deployment.

In phase 9, The Wilcoxon rank-sum tests for 

the CSE SR-100 units show that wet- and drybulb temperatures were significantly higher in 

new units than in deployed units. Since temperature is indicative of chemical reaction, this 

Results and Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 17

could indicate that deployed units have lower 

levels of chemical reaction. Since no statistically significant difference was found with regard 

to CO2 levels between new and deployed units 

(Table 4b), this is not considered an important 

finding.

Results and Discussion
18 Self-Contained Self-Rescuer Long Term Field Evaluation

Laboratory inspection results are shown in Tables 6a and 6b. The failure rate in Phase 8 was 

8% (2 units) of the 24 units collected, and for 

Phase 9 it was 5% (1 unit) of the 20 units collected. Because the OXY K-Plus were not collected at random, these proportions should not 

be viewed as representative of the entire population of Draeger OXY K-Plus in the field.

BMS and Treadmill Tests

Time to depletion, as shown on Figures 8a 

and 8b was comparable for new and deployed 

units. It should be noted that the sample size 

in both phases was small, 24 units in Phase 8 

and 20 units in Phase 9.

The tests of two units were terminated for 

low O2 concentration. These units exhibited 

leakage when evaluated and were later found 

to have internal damage, causing a breach of 

the breathing circuits. Hypoxia (low levels 

of O2) can occur when ambient air (79% of 

which is nitrogen) is drawn into the breathing 

circuit and only the oxygen is removed (by the 

user). These two units were among three that 

had dents in their metal belt-clip plates. Draeger alerted inspectors to look for such dents, 

and has added that to its list of inspection criteria. If the metal belt-clip plate is dented, the 

large, hard-plastic plenum directly inside the 

case can be cracked or shattered, resulting in 

ambient air leakage into the breathing circuit 

(see Figures 9 and 10). Not only can this result 

in low O2 levels, which may cause the user to 

lose consciousness, it can also result in toxic 

gases entering the breathing circuit. Draeger 

submitted a design improvement for certification.

Increased CO2

One deployed unit showed CO2 levels above 

4% (at 65 minutes) before expenditure of the 

O2 supply (at 75 minutes) reaching 5.85% average inhaled CO2. 

Wilcoxon Rank-Sum Test

In Phase 8, the Wilcoxon rank-sum tests for 

the Draeger showed that new units could not 

be distinguished from deployed units in any 

measured parameter.

In Phase 9, the Wilcoxon rank-sum tests for 

the Draeger units show that new units had 

significantly higher O2 concentrations than 

deployed units. Since the lowest test-average 

Table 6. Lab Inspection Results for

Draeger OXY K-Plus

Table 6a. Lab Inspection Results for 

Draeger OXY K-Plus–Phase 8

SN Failure

ARJA 0391 Belt-clip plate dented

ARJA 0393 Belt-clip plate dented

Table 6b. Lab Inspection Results for 

Draeger OXY K-Plus–Phase 9

SN Failure

ARLN 0034 Belt plate dented

Draeger OXY K-Plus Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 19

of the average inhaled O2 concentrations was 

68%, much higher than ambient, this is of no 

concern to users.

One test was terminated simultaneously for 

low O2 concentration and an empty bag at 

92 minutes. This is of no concern to users, 

since an O2 concentration of 15%, and even 

lower, is tolerable for short periods of time. 

One apparatus was missing its back plate and 

should have been removed from service; however, it performed normally.

Figure 9. Dented Draeger OXY K-Plus 

Belt-Clip

Figure 10. Internal damage on Draeger OXY 

K-Plus

Draeger OXY K-Plus Discussion
20 Self-Contained Self-Rescuer Long Term Field Evaluation

Laboratory inspection results are shown in 

Tables 7a and 7b. The failure rate in Phase 8 

was 6% (2 units) of the 35 units collected, and 

for Phase 9 it was 5% (1 unit) of the 20 units 

collected. Because the Life-Saver 60s were not 

collected at random, these proportions should 

not be viewed as representative of the entire 

population of Life-Saver 60s in the field.

BMS and Treadmill Tests

Time to depletion, as shown in Figures 8a and 

8b was different for new and deployed units, 

with the deployed units exhibiting about a 7% 

reduction in time to depletion in both phases. 

Increased CO2

In Phase 8, one deployed unit experienced CO2

levels above 4% two minutes before depletion 

of the O2 supply, while in another unit, breakthrough and depletion occurred simultaneously.

Other Observations

In phase 8, one unit was found with KO2 in the 

mouthpiece. This was taken to MSA for disassembly where the presence of KO2 was confirmed. Eighteen others of similar age and serial number were obtained from various mines 

and inspected. Five of these had signs of KO2

in the base of the breathing hose. MSA revised 

its service life limit to account for the number of hours in mobile use; i.e., the number of 

shifts being worn, stored on equipment, or carried and stored. The unit in question was carried and stored on a 3-shift-per-day schedule 

which accelerated its degradation. A 10-year 

service life still is permitted for ground-storage deployment or mobile use for one 8-hour 

work shift per day, 5 days per week, 52 weeks 

per year (20,800 hours). However, the service 

life maximum for mobile use is now a total of 

20,800 hours which would amount to as little 

as 2.37 years if used 3 shifts per day on a daily 

basis.

Chlorate candles of four units in Phase 8 and 

seven out of 20 units in Phase 9 activated immediately upon opening the apparatus case. 

In phase 9, this occurred on one of three new 

units, also. Although this would not necessarily 

Table 7. Lab Inspection Results for

MSA Life-Saver 60

Table 7a. Lab Inspection Results for

MSA Life-Saver 60–Phase 8 

SN Failure

14076 Case cracked and missing on 

 bottom

14235 Cracks in case bottom

Table 7b. Lab Inspection Results for

MSA Life-Saver 60–Phase 9 

SN Failure

14279 Missing piece of lower case

MSA Life-Saver 60 Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 21

compromise successful use of the apparatus, 

users should be made aware that it could happen.

All tests were terminated for oxygen depletion with empty breathing bags in Phase 9. 

However, one apparatus initially seemed to 

have a compromised chemical bed because the 

volume of the breathing bag slowly dropped 

after being filled by the starter O2 such that it 

was empty at the end of inhalation, approximately four minutes into the test. When it appeared that the test should be aborted or the 

bag refilled, the unit recovered, with the bag 

slowly increasing in volume and behaved normally thereafter. 

Wilcoxon Rank-Sum Test

In both Phase 8 and Phase 9, the Wilcoxon ranksum tests show that new units had significantly 

higher durations and lower inhalation breathing resistance than deployed units. Figures 

8a and 8b show that in Phase 8 and Phase 9, 

the difference in duration between new and 

deployed units is approximately 5 and 7 minutes respectively. Six units had durations of 

less than 60 minutes. While the nearly 50% 

increase in inhalation breathing resistance in 

deployed units is significant (an average of 64 

mm H2O in deployed units, versus 43 mm H2O

in new units), it does not present a problem as 

previously discussed (Hodgson, 1993). 

MSA Life-Saver 60 Discussion
22 Self-Contained Self-Rescuer Long Term Field Evaluation

Laboratory inspection results are shown in Tables 8a and 8b. The failure rate in Phase 8 was 

23% of the 80 units collected, and for Phase 9 

it was 19% of the 57 units collected. Because 

the EBA 6.5s were not collected at random, 

these proportions should not be viewed as 

representative of the entire population of EBA 

6.5s in the field.

Table 8a. Lab Inspection Results for OCENCO EBA

6.5–Phase 8

SN Failure

2F039494 Cracks in case; dented canister

91080173 Long crack in case bottom

92060171 3700 psi

92070150 Small stress cracks in top strap anchors; white dust inside case

92100277 Cracks in case

92100436 Water and mud in-leakage; lower 

strap shifted; clip broken

92120261 Cracks in case at top strap anchors

92120317 Cracks in case at top strap anchors

93010149 Cracks in case bottom lip

93010185 Cracks in case at top strap anchors

93020036 Top strap unattached on one side

93100033 No tamper seals

94100154 Cracks in case under one 

strap-mounted screw

94100320 Dented canister

96110019 Smashed case bottom under strap at 

demand valve

97070097 Cracks in case

97070434 Top strap unattached on one side

98110004 Top strap unattached on one side

Table 8b. Lab Inspection Results for OCENCO EBA

6.5–Phase 9

SN Failure

93050201 Crack in case over demand valve

93110092 Crack in case over demand valve

93110095 Cracks in case at top strap anchors

93120113 Crack in case around demand valve 

inner-anchor

94050007 Shifted cylinder band; dented 

canister; loose screw, washer, and 

bracket from canister-mount; 

exhalation hose twisted on full 

turn

95050296 Shifted cylinder band

95050315 Stress cracks in case bottom under 

demand valve

98110005 Top handle strap unattached on 

one side

99100159 Crack in case bottom near edge of 

demand valve at screw socket

99100211 Mud inside case

100030147 One side of top handle strap 

unattached

Table 8. Lab Inspection Results for OCENCO EBA 6.5

OCENCO EBA 6.5 Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 23

BMS and Treadmill Testing

The oxygen (O2) constant-flow rate is checked 

on the OCENCO EBA 6.5, a compressed-O2 apparatus. The 42 CFR, Part 84 required flow rate is 

1.5 L/min at ambient temperature and pressure, 

dry (ATPD). The large range of average inhaled 

O2 levels in the Phase 8 units is due to the difference in the apparatus O2 regulator flow rates 

(1.51 to 3.30 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 four units, the demand valve stuck open after 

being activated on the first inhalation starting 

the test. In one case, the unit lost 400 psi in the 

first 30 seconds, but then dropped to a normal 

flow, resulting in a 92-minute duration. In another case, the flow was so high that the bag 

filled up and quickly began venting, causing exhalation pressures twice as high as normal. The 

flow rate dropped to the normal range by turning off the O2 cylinder valve and re-opening it; 

and the test continued to 100 minutes. After 

the test, the cylinder was refilled, and the flow 

rates were measured. The initial flow rate was 

1.57 L/min ATPD. After activating the demand 

valve, the flow rate jumped to between 12 and 

16 L/min ATPD, eventually dropping off to 

around 5 L/min, until it was empty at 22 minutes. It is recommended that training on the 

EBA 6.5 mention that, should this happen to 

a user, the flow rate might be able to be reset 

by closing and re-opening the cylinder valve. If 

the user is working hard, however, and is routinely activating the demand valve, there is little 

that can be done to overcome the problem. The 

condition was reported to the manufacturer.

In Phase 9, all tests were terminated due to 

oxygen depletion with empty breathing bags. 

The wide range of average inhaled O2 test averages is due to the difference in the apparatus 

O2 regulator flow rates, which ranged in this 

phase from 1.15 to 3.50 L/min ATPD. 

On one apparatus, the hose that connects the 

CO2 canister to the breathing bag was stuck to 

the CO2 canister and ripped upon attempting 

to unstick it. The apparatus was run on the 

BMS to determine what would happen if worn 

during an actual escape, besides the obvious 

effect of permitting possibly toxic ambient air 

to enter the breathing circuit. The demand 

valve was activated upon each breath, exhausting the O2 supply in 53 minutes. Apparently, 

a significant portion of exhaled breath exited 

the tear in the connector hose and did not enter the breathing bag. Upon inhalation, the lost 

volume was made up through demand valve 

use, drawing down the O2 in the cylinder more 

rapidly than normal.

Increased CO2

In Phase 8, fifteen deployed units experienced 

CO2 levels above 4% before expenditure of the 

O2 supply . None of the new units did so. The 

apparent degradation of the CO2-absorbent 

canister is mitigated by the fact that the CO2

levels did not rise high enough to be noticeable 

to a user, except for one unit that reached 7.3% 

at 111 minutes. In this case, the user would 

probably have experienced some hyperventilation (deeper-than-normal breathing). This 

apparatus was stored on a mining machine 

(Getman tractor) in a 3-shift/day mine for 2 

years and 4 months. 

Other Observations

In Phase 8, many units had small cracks in 

their outer cases, some with internal damage. 

While units with cracks performed normally, 

this points out the problem with inspection 

of this apparatus. Small cracks in the tough 

outer case are evidence of severe impact likely 

to have had more effect on the delicate internal components. The damage eluded detection until the unit reached the testing lab. 

OCENCO EBA 6.5 Discussion
24 Self-Contained Self-Rescuer Long Term Field Evaluation

Only after washing off the caked-on dirt and, 

in some cases, not until the metal straps were 

removed, was the damage revealed. The metal 

straps are normally removed only during the 

donning procedure. It is extremely important, 

then, to thoroughly examine all EBA 6.5 cases 

for any cracks, however small they may be. It 

is recommended that all SCSRs be carefully 

cleaned of caked-on dirt each time they are 

inspected.

Several apparatus had cylinder valves that were 

hard to open; one ultimately required pliers to 

do so.

One apparatus had a large tear in the exhalation 

hose. This was reported to the manufacturer. 

The effect on a user would be that a significant 

portion of exhaled breath would exit the hole 

and not go through the CO2 canister to the 

breathing bag. Upon inhalation, the lost volume could come from ambient, back through 

the hole, and from the demand valve. Excessive 

use of the demand valve would quickly deplete 

the O2 supply. Four apparatus had their lower 

connector hoses somewhat stuck together, resulting in high breathing pressures until they 

were discovered and opened up. The connector hose channels the exhaled air from the 

chemical canister to the breathing bag. A CPIP 

investigation was opened. 

Two cylinder gages had readings over the pressure limit. This turned out to be gage inaccuracy, rather than over-filling of the cylinders. The 

cylinders read 450 and 700 psi when empty. One 

unit was missing a clamp around the exhalation 

breathing hose at the mouthpiece, which came 

apart when the mouthpiece and breathing hose 

assembly was extended to pull out the mouth 

plug for testing. It was reattached and the apparatus performed normally. These problems 

were reported to the manufacturer. 

In Phase 9, numerous apparatus were tested 

that had visible damage indicating they should 

have been removed from service. Six units had 

cracks in their outer cases indicating severe impact and possibly resulting in critical internal 

damage, although not in these apparatus. One 

unit had a visible coating of mud on the inside 

of the case. It functioned normally, however. 

External handle straps were disconnected on 

one side of three units, making them very difficult to open. Another unit had a dented canister, a shifted cylinder band, and an exhalation 

hose that was apparently installed twisted one 

full turn. This unit had the highest test-average exhalation pressure (186 mm H2O) ever 

recorded in any Phase of this study for an EBA 

6.5. It is near the exhalation pressure tolerance 

limit of approximately 200 mm H2O. One unit 

caused violent coughing upon initial donning 

although the test subject was able to continue 

with the test. One unit was found with its relief valve unseated, leaving a huge breach in the 

breathing circuit. Another unit’s neck strap was 

misassembled such that it would not hold a position, and slipped to its full extension. The O2

supply hose of one unit was not attached to the 

breathing bag. The O2 supply hose of another 

one tore when attempting to disconnect it from 

the breathing bag to connect it to the flow meter to check the flow rate. This indicates material decay, although it would not likely have prevented successful use of the apparatus.

Wilcoxon Rank-Sum Test

In both Phase 8 and Phase 9, the Wilcoxon 

rank-sum tests show that new units, statistically, had significantly lower average inhaled 

CO2 values than deployed units, and new units, 

statistically, had significantly lower exhalation 

breathing resistance than deployed units. 

In phase 9, two units had high breathing pressures. These are expected to be within human 

tolerance limits as previously discussed. 

OCENCO EBA 6.5 Discussion
Self-Contained Self-Rescuer Long Term Field Evaluation 25

BMS and Treadmill Testing

Time to depletion, as shown in Figure 8b, was 

comparable for new and deployed units. 

All tests were terminated with empty breathing 

bags due to oxygen depletion, with one treadmill test simultaneously reaching 4% CO2.

Wilcoxon Rank-Sum Test

No data were collected for the OCENCO 

M-20 for Phase 8 testing. In Phase 9, the Wilcoxon rank-sum tests show that deployed units 

cannot be distinguished from new units in any 

performance measure.

Other Observations

Five units were missing one or more of their 

external rubber bumpers, which should have 

necessitated removing them from service. Two 

were found with LiOH (Lithium Hydroxide) 

powder in the breathing bag, one of which was 

missing both top bumpers. The LiOH powder 

in the breathing bag would not have prevented 

successful use of the apparatus. Six apparatus 

showed evidence of mine dust leakage into the 

cases, again apparently not affecting performance to a significant degree.

Table 9. Lab Inspection Results for

 OCENCO M-20–Phase 9

SN Failure

513354 Top bumpers missing

513406 One top bumper missing

513445 Ball-bearing tamper seal missing

513488 One top bumper missing

513500

Bottom bumper and one of two 

top bumpers missing

513502 Top bumpers missing

Laboratory inspection results are shown in Table 9. The failure rate in Phase 9 was 30% of the 20 

units collected. 

OCENCO M-20 Discussion
26 Self-Contained Self-Rescuer Long Term Field Evaluation

The results of this study indicate that the mining environment seems to have caused some 

performance degradation in all the apparatus 

to some degree. The deployed CSE SR-100s 

tested in this phase exhibited CO2 levels exceeding 4% (74% of all units tested, with 29% 

of these occurring before 60 minutes); stucktogether breathing hoses (10%), some leading 

to tearing; starter-O2 failure (10%); breathing hose punctures and tears (9%); breathing pressures exceeding +200 mm H2O or 

-300 mm H2O (8%); and loose particulates 

in the breathing hose. The loose particulates 

caused coughing in human-subject tests. In 

addition, it was found that if the case had sustained an impact toward the top where the 

inner canister seal is located; the seal could 

become distorted, permitting extremely irritating bed chemicals to escape into the breathing circuit. If the orange plastic case springs 

back after such an impact instead of cracking, 

this type of damage would escape visible detection. CSE addressed these issues through 

the deployment of the induced noise test, 

improved inspection criteria, the addition of 

a heat indicator, and upgraded assembly and 

packing procedures.

The Draeger OXY K-Plus exhibited a similar 

problem in that impact in the area of its metal 

belt-clip can crack or shatter an internal component, permitting in-leaking of the ambient 

air. While this damage is subtle, it is detectable, 

because the metal belt-clip is permanently 

deformed from any such impact. Specific inspection for this damage has been added to the 

OXY K-Plus’s overall inspection criteria within 

the user’s instructions.

A 7% reduction in capacity has been observed in 

the MSA Life-Saver 60 among apparatus tested 

in this phase. In addition, bed chemical leakage 

into the breathing circuit was found in one unit. 

Upon further investigation in cooperation with 

MSA, KO2 was found in the breathing circuits 

of five other units. MSA has now revised the expected service life of the Life-Saver 60 to be a total of 20,800 hours of mobile use (10 years of 8-

hour work shifts, 5 days per week, 52 weeks per 

year), defined as any deployment mode other 

than ground storage. 

The OCENCO EBA 6.5 is showing some bed 

degradation leading to CO2 levels above 4%, 

though not to a degree affecting successful use. 

A small number of units had demand valves 

that seemed to stick open when activated. In 

most cases, the high flow rate quickly dropped 

off to normal levels. In one case, however, it 

would have emptied the cylinder in 22 minutes, as evidenced by actually refilling the 

cylinder and activating the demand valve, as 

would happen in actual use. Several units had 

cylinder valves that were very hard to open; 

one required pliers. One unit had a tear in the 

breathing hose, and another was missing an 

exhalation hose clamp. All of these conditions 

were reported to the manufacturer. Although 

field inspection seems to be improving, we still 

found many EBA 6.5 units with disqualifying 

cracks in the cases. It is further recommended 

that units having any cracks in the case be removed from service. 

Because of the importance of effective visual 

inspection, it is recommended that deployed 

apparatus of all types be cleaned of mine dirt 

for their 90-day inspections. 

An interagency agreement between MSHA 

and NIOSH has created Care and Maintenance Training Modules for the five currently 

Long Term Field Evaluation Phase 8 Summary
Self-Contained Self-Rescuer Long Term Field Evaluation 27

approved SCSRs. These training modules focus 

on the details of proper care and maintenance 

for SCSRs, and emphasize the importance of 

critical daily inspection.

Long Term Field Evaluation Phase 8 Summary
28 Self-Contained Self-Rescuer Long Term Field Evaluation

The results of this study suggest that some 

performance degradation was observed. The 

CSE SR-100s exhibit problems with CO2 levels exceeding 4% (65% of all units tested, with 

29% of these occurring before 60 minutes); 

stuck-together breathing hoses (19%) which 

were prone to tear; starter-O2 failure (16%); 

breathing hose punctures and tears (9%); 

breathing pressures exceeding +200 mm H2O

or -300 mm H2O (36%); and loose particles in 

the breathing hose (31%). The loose particles 

caused coughing in all human-subject tests. 

A 7% reduction in capacity was observed in 

the MSA Life-Saver 60 among apparatus tested in Phase 8. In this Phase 9, we observed a 

10% reduction in capacity with six units having durations less than 60 minutes.

For the OCENCO EBA 6.5, evidence of degradation and mechanical integrity loss were 

observed. A twisted exhalation hose caused the 

highest exhalation breathing pressures ever 

recorded in an EBA 6.5. Other manufacturing oversights were an unseated relief valve, a 

misassembled neck strap that would not hold 

a set, and an unattached O2 supply hose. Two 

examples of material decay were identified: a 

connector hose stuck to the bottom of the CO2

canister that tore when attempting to open up 

the flow path, and an O2 supply hose that tore 

when attempting to perform the O2 flow test. 

Although field inspection seems to be improving, six EBA 6.5s had disqualifying cracks in 

the cases, and three units had missing external 

handle straps, making it difficult to open the 

cases. 

Because of the importance of effective visual 

inspection, it is recommended that deployed 

apparatus of all types be cleaned of mine dirt 

for their 90-day inspections.

Long Term Field Evaluation Phase 9 Summary
Self-Contained Self-Rescuer Long Term Field Evaluation 29

The Long Term Field Evaluation (LTFE) program for self-contained self-rescuer respirators 

for miners was initiated more than 20 years 

ago by the U.S. Bureau of Mines. The objective 

for the LTFE program is to obtain data to compare performance of mine deployed SCSRs to 

new SCSRs. LTFE program results based on 

scientific principles can provide useful information to monitor SCSR performance degradation due to the physical stresses of mine use 

and can be a useful indicator for the expected 

performance of deployed SCSRs. However, aspects of the current LTFE program limit the 

generalizability of the evaluation results. These 

program aspects are:

SCSR sampling,

SCSR test procedure,

LTFE program alignment with 

certification program

SCSR LTFE reporting.

Redesign of the LTFE to address these program aspects is under development by NIOSH 

NPPTL and will be implemented following 

peer review, stakeholder input, and completion of Phase 10 testing in the current LTFE 

program. Considerations for the redefined 

LTFE are:

SCSR Sampling

A systematic stratified sampling scheme will 

enhance the representativeness of the evaluated SCSRs. The sampling strategy may need 

to account for mine size, differences in deployment strategy, carried versus stored units, and/

or the manufacture date of SCSRs. 

•

•

•

•

Along with stratification factors the total 

number of sampled SCSRs to achieve statistical significance for program results needs to 

be evaluated. Continued activities to increase 

both the total number of deployed SCSRs and 

mine deployment strategies will have an impact on the sampling strategy used for the redesigned LTFE program. 

SCSR Test Procedure

Current LTFE program testing is different 

from testing used for certification of SCSRs 

to the requirements of 42 CFR, Part 84. SCSR 

evaluation testing for certification relies on a 

series of bench tests and human subject tests 

(man tests) to establish conformance with the 

requirements specified in 42 CFR, Part 84. 

Current LTFE program evaluations are based 

on laboratory testing to evaluate SCSR performance using a combination of machine tests 

and human subject tests. For the machine tests 

a breathing and metabolic simulator (BMS) 

is used to test SCSRs to an end point, oxygen 

depletion. The BMS operational parameters 

are selected to provide a constant and repeatable physiological work rate. The current 

LTFE program tests are expected to remain in 

the redefined LTFE program. BMS testing at 

a constant rate to obtain an operational end 

point is a reliable and repeatable means of 

evaluation. The primary test procedure difference anticipated for the redesigned LTFE 

program is that each phase of testing will also 

include testing of new SCSRs to establish a 

performance baseline. The baseline data may 

be useful for evaluating the trend of SCSR 

manufacturing output and for comparing 

deployed SCSR degradation. Evaluation test 

Redesigned Long Term Field Evaluation 
30 Self-Contained Self-Rescuer Long Term Field Evaluation

results are expected to consider only the life 

support capability of the tested SCSR: oxygen 

supply, carbon dioxide removal and capacity 

or duration. The life support parameters for 

oxygen and carbon dioxide concentrations 

will be established based on physiologically 

acceptable limits for the expected duration of 

the SCSR. 

LTFE Program Alignment With 

Certification Program

The newly designed LTFE program will better 

align the SCSR evaluations with the respirator 

certification program. The certification program, in evaluating conformance with 42 CFR 

Part 84 requirements, requires the manufacturers to project the usable service life of deployed 

units and to establish quality controls in the 

manufacture of new units. NIOSH intends 

to augment existing LTFE testing with audit 

testing of new SCSRs to evaluate continued 

conformance with certification requirements, 

annual manufacturing site quality audits to 

evaluate conformance with the NIOSH certified quality plan, and documented corrective 

actions resulting from problem investigations. 

SCSR Reporting

More regular reporting of LTFE program results is expected under the redesigned program. The new reports will include results of 

evaluation testing, follow-through corrective 

actions to address issues observed during evaluation, and verification of manufacturer site 

quality audits. 

Redesigned Long Term Field Evaluation
Self-Contained Self-Rescuer Long Term Field Evaluation 31

Phase 8

MSHA District 1 Office, Wilkes-Barre, PA

D&D Primrose Slope, Donaldson, PA

M&M Coal Co., Mercury Slope, Hegins, PA

Rhen Coal Co., Skidmore Slope, Pine Grove, PA

RS&W Coal Co., RS&W Drift, Klinserstown, PA

MSHA District 2 Office, New Stanton, PA

Consolidation Coal Co., Mine No. 84, Eighty Four, PA 

Cyprus Emerald Res. Corp., Emerald Mine No.1, 

Waynesburg, PA

Consolidation Coal Co., Bailey Mine, Graysville, PA

Consolidation Coal Co., Enlow Fork, West Finley, PA 

MSHA District 3 Office, Morgantown, WV

BJM Coal Co., Mine No. 9A, Summerville, WV

Red Bone Mining Co., Crawdad No.1 Mine, 

Morgantown, WV

Coastal Coal, Whitetail Kittanning Mine, Newberg, WV

Scorpio Mining Inc., Laurel Run Mine, Fairmont, WV

Steyer Fuel Inc., Steyer Mine, Newberg, WV

MSHA District 4 Office, Mt. Hope, WV

BAR-K Inc., Madison, WV

Mountaineer Alma-A, Mingo Logan Mine, 

Wharncliffe, WV

Laurel Creek No. 1, Dingess, WV

Laurel Creek No. 3, Dingess, WV

MSHA District 5 Office, Norton, VA

Paramount Coal Corp., Deep Mine #28, Dante, VA 

Har-Lee Mine #10, Clintwood, VA

Island Creek Coal Co., VP8, Oakwood, VA

MSHA District 6 Office, Pikeville, KY

Excel Mining LLC, Mine No. 2, Pilgrim, KY

McCoy Elkhorn Coal Corp., Mine # 21, Kimper, KY

Lodestar Energy Inc., Miller Creek Mine #1, Pikeville, KY

Consol of Kentucky, Rhoades Branch H-4, Deane, KY

South Akers Mining #8, Pikeville, KY

MSHA District 7 Office, Barbourville, KY

BR&D Enterprises Inc., BR&D #3, Middlesboro, KY

Kentucky May Mining, Kite, KY

Mallie Coal Co., Inc., Mine #4, Woodbine, KY

Minton Hickory Coal Co., Mine # 9, Corbin, KY

Blue Diamond No. 74, Slemp, KY

MSHA District 8 Office, Vincinnes, IN

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

Consolidation Coal Co., Rend Lake Mine, Sesser, IL

Wabash Mine Holding Co., Wabash Mine, Keensburg, IL

MSHA District 9 Office, Denver, CO

Energy West Mining Co., Deer Creek Mine, 

Huntington, UT

C W Mining CO-OP, Mine Bear Canyon #1, 

Huntington, UT 

Bowie #2 Mine, Paonia, CO

MSHA District 10 Office, Madisonville, KY

Baker Mine, Sturgis, KY

Peabody Coal Co., Camp 11 Mine, Henderson, KY

Dotiki Mine, Henderson, KY

Cardinal Mine, Morton’s Gap, KY

Island Mine #1, Madisonville, KY

MSHA District 11 Office, Birmingham, AL

North River #1 Mine, Berry, AL 

Jim Walters Resources, Inc., #4 mine, Brookwood, AL

Jim Walters Resources, Inc., #5 mine, Brookwood, AL

Jim Walters Resources, Inc., #7 mine, Brookwood, AL

US Steel Mining Co., Oak Grove Mine, AL

Drummond Co., Shoal Creek Mine, Jasper, AL 

Phase 9

MSHA District 1 Office, Wilkes-Barre, PA

B and B Coal Co., Rock Ridge No. 1 Slope, Tremont, PA

Buck Mt. Slope, Tremont, PA

Harmony Mine, Mt. Carmel, PA

Jordan #1 Slope, Shamokin, PA

Little Buck Coal Co., No. 2 Slope, Pine Grove, PA

No. 1 Slope, York, PA 

RS&W Coal Co., RS&W Drift, Klingerstown, PA

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 this study:

Acknowledgments 
32 Self-Contained Self-Rescuer Long Term Field Evaluation

MSHA District 2 Office, New Stanton, PA

Maple Creek Mining Inc., Bentleyville, PA

Mountain Springs Coal, Shippingport, PA

MSHA District 3 Office, Morgantown, WV

Crafts Run Mine, Dana Mining Co., Morgantown, WV

Difficult Mining Inc. Johnstown #1, Johnstown, PA

Flag Run Mining, M&J Coal Co. Inc., Bridgeport, WV

Ryanstone No. 1 Mine, Philippi, WV

Spruce #1, Buckhannon, WV

Steyer Mine, Steyer Fuel, Inc., Newberg, WV

MSHA District 4 Office, Mt. Hope, WV

Elk Run Coal Co., Black King #1 Mine, Sylvester, WV

Harmon Branch Mining, Inc., Caretta, WV

Island Fork Construction 36 Mine, Beckley, WV

Laurel Creek No. 4, Dingess, WV

Rock N Roll Coal Co., Inc., Mohawk, WV

US Steel Mining Co., # 50 Mine, Pineville, WV

MSHA District 5 Office, Norton, VA

Apollo Mining #1, Bristol, VA

Buchanan Mine #1, Mavisdale, VA

Cherokee Mine, Haysi, VA

Four “O” Mining Co., Vansant, VA

MSHA District 8 Office, Vincennes, IN

Air Quality Mine #1, Black Beauty Coal Co., Evansville, IN

Freeman United Coal Co., Crown II mine, Vinden, IL

Triad Underground Mining, L.L.C., Edwardsport, IN

MSHA District 10 Office, Madisonville, KY

Dotiki Mine, Nebo, KY

KenAmerican Resources Inc., Central City, KY

Acknowledgements
Self-Contained Self-Rescuer Long Term Field Evaluation 33

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 secondgeneration 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, Shubilla JP [2002]. Self-contained self-rescuer field evaluation: seventh-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. 2002-127, 

RI 9656.

Kyriazi N, Kovac JG, Shubilla JP, Duerr WH, Kravitz 

J [1986]. Self-contained self-rescuer field evaluation: 

first-year results of 5-year study. Pittsburgh, PA: U.S. 

Department of the Interior, Bureau of Mines, RI 9051.

NIOSH 1994. Documentation for immediately dangerous to life or health concentrations (IDLH): NIOSH 

Chemical Listing and Documentation of Revised IDLH 

Values. NTIS Publication No. PB-94-195047

References
34 Self-Contained Self-Rescuer Long Term Field Evaluation

Appendix 1—Certified Product Investigation

Program (CPIP) Investigations

Initiated From LTFE 8 & 9

Task Number Date Opened Date Closed Mfg. Description Approval Number Resolution

CSE SR-100

11813 1/2/2001 1/16/2001 CSE

SR-100 -

Two units 

tested at PRL 

did not fire 

when 

activated. TC-13F-0239

Units cold 

started 

successfully

12022 6/22/2001 7/9/2001 CSE

SR-100 No 

starter 

oxygen in 

cylinder Unit 

S/N 57942 TC-13F-0239

Unit cold 

started 

successfully

Ocenco EBA 6.5

12023 6/22/2001 3/21/2005 OCN

High oxygen 

flow rate 

resulting in 

low duration 

on a 

simulator test 

- Valve hard 

to turn TC-13F-0104

Isolated 

Incident.

12202 11/8/2001 8/5/2002 OCN

EBA 6.5 

High oxygen 

flow found 

during LTFE 

at NPPTL TC-13F-0104

Outside 

condition of 

use/failed 

visual 

inspection

12236 12/18/2001 3/23/2004 OCN

EBA 6.5 -

Torn 

(deteriorated) 

breathing 

hose 

discovered 

by LTFE TC-13F-0104

Breathing 

hose 

deteriorated 

from 

exposure to 

strong 

sunlight.

12310 2/25/2002 8/5/2002 OCN

Clamp 

missing from 

hose end TC-13F-0104

Determined 

to be an 

isolated 

case. 

Inspection 

criteria reemphasized

12517 5/21/2002 2/15/2004 OCN

New unit 

EBA 6.5 -

bulged case 

seal and 

oxygen TC-13F-0104

Warranty 

issue, 

readily 

identifiabel 

by user
Self-Contained Self-Rescuer Long Term Field Evaluation 35

Appendix 2—Test Results

Figure A2-1. CSE SR-100 Test Results Phase 8
36 Self-Contained Self-Rescuer Long Term Field Evaluation

Figure A2-2. Draeger OXY K-Plus Test Results Phase 8

Appendix 2—Test Results
Self-Contained Self-Rescuer Long Term Field Evaluation 37

Figure A2-3. MSA Life-Saver 60 Test Results Phase 8

Appendix 2—Test Results
38 Self-Contained Self-Rescuer Long Term Field Evaluation

Figure A2-4. Ocenco EBA 6.5 Test Results Phase 8

Appendix 2—Test Results
Self-Contained Self-Rescuer Long Term Field Evaluation 39

Figure A2-5. CSE SR-100 Test Results Phase 9

Appendix 2—Test Results
40 Self-Contained Self-Rescuer Long Term Field Evaluation

Figure A2-6. Draeger OXY K-Plus Test Results Phase 9

Appendix 2—Test Results
Self-Contained Self-Rescuer Long Term Field Evaluation 41

Figure A2-7. MSA Life-Saver 60 Test Results Phase 9

Appendix 2—Test Results
42 Self-Contained Self-Rescuer Long Term Field Evaluation

Figure A2-8. Ocenco EBA 6.5 Test Results Phase 9

Appendix 2—Test Results
Self-Contained Self-Rescuer Long Term Field Evaluation 43

Figure A2-9. Ocenco M-20 Test Results Phase 9

Appendix 2—Test Results
44 Self-Contained Self-Rescuer Long Term Field Evaluation

Appendix 3—ASMD Test Results

Figure A3-1a. CSE SR-100 Decibel Level versus CO2 Level Phase 8

Figure A3-1b. CSE SR-100 Decibel Level versus CO2 Level Phase 9
For information about occupational safety and health topics contact NIOSH at:

1–800–35–N IOSH (1–800–356–4674 )

Fax: 513–533–8573

E-mail: pubstaft@ cdc.gov

www.cdc.gov/niosh

S AFE R • H E ALT H IE R • P E OP L ET M

DHHS (NIOSH) Publication No. 2007–103

Delivering on the Nation’s promise:

Safety and health at work for all people

through research and prevention