PPE CASE

Personal Protective Equipment Conformity Assessment Studies and Evaluations

Point-of-Use Assessment for Self-Contained Self-Rescuers 

Randomly Sampled from Mining Districts: First Phase 

Sample Period: May 2009 to July 2010

Christopher Coffey, David Murray, and Frank Palya

National Institute for Occupational Safety and Health

National Personal Protective Technology Laboratory

Abstract 

The National Personal Protective Technology Laboratory (NPPTL)1 of the National Institute for Occupational 

Safety and Health (NIOSH) has undertaken a study to evaluate the long-term field performance and reliability of 

self-contained self-rescuers (SCSRs) deployed in U.S. underground coal 

mines in accordance with the use and location requirements of Title 

30 Code of Federal Regulations (30 CFR) Part 75.1714. This ongoing 

project provides visual inspection data and performance data on field 

deployed SCSRs. 

This report presents findings from the first phase of the SCSR LongTerm Field Evaluation Program (LTR1). The Mine Safety and Health 

Administration (MSHA) maintains a list of deployed SCSRs in the 

United States. From the MSHA list, NIOSH randomly selects 140 units 

each from four models to attempt a field collection of 100 SCSRs per 

model for laboratory testing. One hundred and forty units are chosen

to allow for issues with obtaining specific units. The SCSRs that pass 

the manufacturer’s recommended visual inspection at the mine are 

collected and further evaluated by NPPTL including a second visual 

inspection, leak testing, gas flow testing, and breathing and metabolic 

simulation (BMS) testing. The tests performed in this study are not 

respirator approval tests; however, poor performance during testing 

led to the opening of a certified product investigation process (CPIP) 

on one SCSR model. The data obtained for the one model that 

underwent the CPIP investigation was reported in a Department of Health and Human Services numbered 

document that is posted on the NIOSH website. 

 1 A list of acronyms and abbreviations is available in Appendix A.

NIOSH’s point-of-use 

assessments for selfcontained self-rescuers 

(SCSRs) found that mine 

operators are largely 

compliant with SCSR 

manufacturer-specified 

requirements and the 

devices tested appear to 

be sufficiently designed 

for mining use conditions.
2

 

 

Overall, 85% of the SCSRs examined at NIOSH passed the visual inspection. The BMS test results indicate that 

99% of SCSRs that pass the manufacturer’s recommended visual inspection criteria demonstrated acceptable 

rated service life. Of the three SCSRs with unacceptable service lives, only one failed the visual inspection. Most 

of the respirators failing the visible inspection in this phase of the study would have met the BMS testing criteria 

or been removed from service, if the manufacturer’s recommended cleaning, handling, and visual inspection 

had been performed properly. There were no discernible trends from BMS, leak tests, or flow tests that might 

indicate or predict an end-of-service-life for any SCSR model.

The most frequent limitations in the collection of SCSRs from the mines could be partially overcome through 

better communication with the mines and district offices, and by obtaining a more recent and expanded 

inventory list from the MSHA electronic SCSR inventory. This phase of the LTR1 study demonstrates the need to 

expand collection options to meet the quota of 100 SCSRs from each manufacturer, and ultimately retain the 

desired statistical validity of the study.

Introduction

U.S. coal mine operators are required to provide to each underground coal miner a SCSR. Additional SCSRs are 

required to be stored in caches on working sections and in outby escape ways. Title 30 Code of Federal 

Regulations (30 CFR) Part 75.1714 requires that each person in an underground coal mine wear, carry, or have 

ready access to a device that provides respiratory protection with an oxygen (O2) source for at least one hour, as 

approved by the certifying agencies, NIOSH and MSHA. In some mines, shorter duration SCSRs are also available 

to reach caches of one-hour units. Together, the agencies conduct long-term field evaluations (LTFE) of SCSRs 

deployed in U.S. underground coal mines to assess the reliability and performance of the SCSRs.

In the first ten phases of the long-term field evaluation, referred to as LTFE 1 through 10, NIOSH targeted SCSRs 

deployed in underground coal mines for the longest period of time exhibiting signs of environmental impact for 

collection. Previous reports describe phases 1 through 10 (Kyriazi et al. 1986; Kyriazi and Shubilla 1992, 1994, 

1996, 2000, 2002; NIOSH 2006, 2008). The LTFE phases 1 through 10 were successful at identifying performance 

and reliability issues, and resulted in SCSR product improvements; however, the sample size and criteria limited 

the results in statistical validity. 

In 2009, the formation of a new sampling strategy allowed randomization of the SCSR population tested. The 

new sampling plan increases the statistical significance of observations made in the LTFE study. The new 

sampling plan is designed to result in a 98% chance of detecting a failing respirator when the true error rate is 

1.5% or more. From 2009 forward, NIOSH referred to the collections as Long-Term Random Field Evaluation 

Phase 1 (LTR1), LTR2, et cetera to indicate the randomization of the sample and the phase of collection.

Beginning with the LTR1 collection, NIOSH subjects the respirators to strict visual inspection following the 

manufacturer’s user instructions. This allows only units that should be in field use into the study and eliminates 

testing units that do not meet the manufacturer's visual inspection criteria for continued deployment. NIOSH 

bases LTR1 collection on a random sampling protocol negating the influence of different mining environments; 

such as coal seam height, size of the mine, and other environmental factors as a bias in the sample. The current 

LTR collection strategy targets the same number of each SCSR model approved for use in underground coal 

mines, regardless of market share. 
3

 

 

Methods

Self-Contained Self-Rescuer Respirators 

The SCSRs tested in this LTR1 phase were the Dräger Oxy K Plus, Ocenco EBA 6.5 and M-20 models (Figures 1 

through 3), and the CSE SR-100 (Figure 4). The CSE SR-100 testing revealed that some units did not produce 

enough starter oxygen to allow for safe escape in the event of a mine emergency. NIOSH initiated an 

investigation into the sources of this problem. As a result, the NIOSH approval was rescinded and MSHA 

required the units to be removed from service no later than December 31, 2013. The results of the CSE SR-100 

investigation are detailed elsewhere and are not discussed in this report (Ahlers, 2012).

Figure 1. Dräger Oxy K Plus SCSR Figure 2. Ocenco EBA 6.5 SCSR

Figure 3. Ocenco M-20 SCSR Figure 4. CSE SR-100 SCSR

The Dräger Oxy K Plus is a chemical oxygen producing SCSR that employs an oxygen starter apparatus for initial 

performance and is rated for a 60-minute service life. The Ocenco EBA 6.5 and M-20 are closed-circuit 

compressed oxygen SCSRs. The EBA 6.5 has a rated duration of 60 minutes; the M-20 has a rated duration of 10 

minutes. All SCSRs included in the study utilize a chemical bed to keep carbon dioxide within acceptable limits 

for use.
4

 

 

Sampling Strategy

For this phase of the statistical analyses, NIOSH targets collection of 100 each of these NIOSH-approved SCSR 

models deployed in United States underground coal mines. NIOSH receives a list of SCSR serial numbers across 

all mining districts using the MSHA SCSR Inventory and Report. NIOSH uses this list to select units for future 

collections. From the MSHA list, NIOSH randomly selects 140 units of each model to allow for issues collecting

units. Selecting 140 units increases the likelihood of a field collection of 100 SCSRs per model for laboratory 

testing. 

Visual Inspection

NIOSH performs a visual inspection of each unit using the manufacturers’ recommended visual inspection

procedure upon receipt of each SCSR at the Pittsburgh facility. Most manufacturer’s recommended visual 

inspections of SCSRs focus on the integrity of the case, latches, and indicators that are viewable without opening 

the respirator. If all visual inspections pass, the respirator should be safe for use. 

Quantitative Leak Test 

Respirators that pass visual inspection are subjected to the quantitative leak test (QLT) to assess breathing 

circuit integrity. This is an additional test which is not required by 42 CFR 84 for approval testing. The leak test 

uses a 300 mm of water (mm H2O) vacuum and measures the inward leakage in milliliters per minute (mL/min). 

At maximal work rates, inhalation pressures should not exceed 300 mm H2O or 500 mL/min of inward leakage to 

reasonably assure user protection for a period of 1 hour. The inward leakage threshold of 500 mL/min was 

developed using the one-hour threshold limit value (TLV) for carbon monoxide (CO) which is 200 ppm. An 

inward leakage rate of 500 ml/min in a 10% CO atmosphere at a peak inhalation rate of 250 liters per minute 

(L/min), which coincides with an oxygen consumption rate of 3.0 L/min, would lead to an inward leakage of 200 

ppm CO, the one-hour TLV. Based on this reasoning, a quantitative leak measurement should be less than 500 

ml/min. 

Gas Flow Test

After assessing the breathing circuit integrity, NIOSH could only test the Ocenco EBA 6.5 model for maximum 

sustained oxygen flow rate because it uses compressed oxygen and is manufactured with valves to turn the 

oxygen flow on and off. This was performed by disconnecting the oxygen supply line from the breathing bag, 

connecting it to a flow meter, and fully opening its oxygen supply valve for approximately 30 seconds. The 

maximum sustained oxygen flow rate was subsequently recorded and the supply valve was fully closed. The 

oxygen supply line was subsequently reattached securely to the breathing bag connector using a wire tie.

This test is part of the approval process described in Title 42 Code of Federal Regulations, Part 84, §84.94, Gas 

flow test; closed-circuit apparatus (Code of Federal Regulations, 2014). For combination constant flow and ondemand SCSR units, this approval regulation requires a minimum constant flow rate of 1.5 L/min. If the 

maximum sustained oxygen flow rate is greater than or equal to 1.5 L/min, the unit meets this test 

requirement. None of the Ocenco EBA 6.5 SCSR units tested at the NIOSH laboratory had maximum sustained 

oxygen flow rates below this limit.

Breathing and Metabolic Simulation (BMS) Test

SCSR performance is then evaluated using a BMS test. The computer-controlled BMS produces CO2 and 

simulates O2 consumption at fixed breathing frequencies and tidal volumes to simulate human metabolic 

processes (Deno, 1984 and Kyriazi, 1986). The BMS is an ideal device for evaluating inhaled CO2 and O2

concentrations in respirators due to its high degree of accuracy and repeatability in duplicating human CO2

production and O2 consumption. Also, the BMS continuously measures the inhalation air temperature (dry bulb 

and wet bulb) and inhalation and exhalation pressure resistance. By design, a BMS replicates breathing 
5

 

 

ventilation (respiratory frequency, tidal volume, flow, temperature, and humidity), O2 consumption, and CO2

production. A BMS produces human respiratory air qualities at approximately 33°C and saturated with water 

vapor. The computer uses a routine of energy expenditures (protocol) to make adjustments and provide 

measurements of respiratory gas concentrations, pressures, and temperatures (Figure 5).

The SCSR units tested in this phase were not certified using the BMS test. The units were certified using Mantest 4 for the stated service time (either 10 or 60 minutes), as described in 42 CFR Part 84, Subpart H. Due to 

resource constraints, it was not feasible to conduct Man-test 4 on 400 SCSRs. The BMS test was used as a 

surrogate for Man-test 4. 

NIOSH tested the SCSRs on the BMS using a constant average metabolic work rate test (Table 1). The constant 

average work rate used is similar to the 50th percentile miner (body weight of 87 kg or 192 lbs.) performing the 

one-hour Man-test 4 as described in 42 CFR 84, Subpart H. NIOSH programmed the BMS to run at a VO2 of 1.35 

L/min, VCO2 of 1.15 L/min, a ventilation rate of 30 L/min, and respiratory frequency of 18 breaths per minute. 

Tests on 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%. When these limits are exceeded, the BMS gas metabolism is 

compromised and further data are not acceptable for analysis. In this study, the BMS testing was deliberately 

conducted beyond the SCSR rated service life until the breathing gas supply was expended. 

Although the average work rate is the same, the LTR testing is not equivalent to approval testing. 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. However, the BMS can be used to provide an indication of SCSR duration performance. Approval testing

under 42 CFR 84, Subpart H using human subjects imposes high and low work rates that the average work rate 

used in the LTR does not. Also, the stressor levels are continuously monitored in the LTR, whereas the stressor 

levels are sampled only between work activities performed by the human subjects in approval testing. In 

addition, LTR testing continues until the apparatus is empty or stressor levels exceed allowable parameters;

whereas testing during approval ends at the rated duration, even if the capacity of the apparatus exceeds it.

 Figure 5. Automated Breathing and Metabolic Simulator
6

 

 

Table 1. Constant Average Metabolic Work Rate

Metabolic workload Rate

O2 Consumption 1.35 L/min

CO2 Production Rate 1.15 L/min

Ventilation Rate 30 L/min

Tidal Volume 1.68 l/breath

Respiratory Frequency 17.9 breaths/min

Peak respiratory flow rate:

 Peak Inhalation 89 L/min

 Peak Exhalation 71 L/min

The performance requirements for the tests conducted during this evaluation are identified in Table 2. 

Table 2. SCSR Performance Requirements

Parameter Requirement

Quantitative Leak Test < 500 ml/min

Gas Flow ≥ 1.5 L/min

Inhaled CO2 Concentration* < 1.5 %

Inhaled O2 Concentration* > 19.5%

Breathing Peak Pressure* ≤ 200 mm H2O

Wet Bulb Temperature* < 43oC

 * 42 CFR 84.303 Acceptable Operating Minute Average 

Units giving results not meeting the rated duration and those that fall under 42 CFR 84.41 regarding quality 

control plans had a report filed with the certified product investigation process (CPIP) coordinator for 

investigation into the cause of these results and to determine if any further action was warranted.

Results and Discussion 

Sampling Results

In LTR1, as described previously, NIOSH randomly selected 560 units (140 of each of the four models) from the 

MSHA list. Of the 560 units selected, it was only feasible for NIOSH to collect 517 SCSRs from the mines for 

various reasons such as it is not economic to collect just one unit from a remote mine. Figure 6 depicts the 

status of the 560 SCSRs randomly selected in the LTR1 collection. Of the 517 SCSRs requested for collection, a 

total of 185 SCSRs were either missing, not available, or removed from service. This amounts to 35.8% of the 

respirators on the NIOSH random selection list. In order to improve future collection efforts, NIOSH will explore 

communication strategies for confirming SCSR status prior to collection and a means of reaching smaller mines 

that may only have one unit to collect. The NIOSH Pittsburgh facility received 332 SCSRs for testing, yielding a 

collection rate of 64.2%. However, four of the units received did not pass visual inspection at the mine and 

should not have been sent. Although the 64 collected CSE SR-100 units were BMS tested, the results are

reported elsewhere (Ahlers, National Personal Protective Technology Laboratory, 2012) and are not included in 

this report. The BMS data from 12 tests was not usable; therefore, the results from the remaining 315 units 

were the basis of these findings. 
7

 

 

Figure 6. LTR1 Collection Dispersion

NIOSH attained 87 of the 140 Dräger Oxy K Plus SCSRs listed on the LTR1 targeted collection list, yielding a 

collection rate of 62%. Challenges affecting the collection of Dräger Oxy K Plus SCSRs include: the closure of 

mines leading to the unavailability of 21 SCSRs and communication issues within one of the mining districts 

which made 14 Dräger Oxy K Plus units unavailable. These two challenges alone resulted in 25% of the Dräger 

Oxy K Plus SCSRs on the targeted collection list being deemed unavailable.

NIOSH collected 103 of the 140 Ocenco EBA 6.5 SCSRs on the targeted LTR1 collection list, yielding a collection 

rate of 74%. Ocenco EBA 6.5 SCSRs were the most prevalent SCSR deployed in U.S. underground coal mines at 

the time of collection, holding roughly 60% of the market share. Therefore, this respirator model was easier to 

attain than other models in this study. LTR1 methods call for the collection of 100 EBA 6.5, but due to the 

shortfall in other collection areas, NIOSH accepted 103 units into the study. 

NIOSH collected 61 of the 140 Ocenco M-20 SCSRs on the targeted LTR1 collection list, yielding a collection rate 

of 44%. Challenges affecting the collection of M-20 SCSRs include: the closure/non-production status of mines 

leading to the unavailability of 46 respirators and 28 M-20s reported as missing by the mine. This eliminates 53% 

of the targeted collection list for M-20 respirators in the LTR1 from collection.

As noted previously, NIOSH did collect CSE SR-100. Sixty-four of the 140 CSE SR-100 SCSRs on the targeted LTR1 

collection list were collected, yielding a collection rate of 46%; however, as stated previously, further CSE SR-100 

results are not presented in this report.

Visual Inspection

All units were inspected using the manufacturer’s recommended visual inspection criteria after being cleaned. 

Despite having passed the inspection during collection, some collected units were judged to have failed the 

manufacturer’s recommended visual inspection criteria once received in the laboratory as described below. In 

other words, these units should have been removed from service and not been available for the LTR1 tests. 

Failure could be attributed to differences in judgment as to the compliance with inspection criteria. This reflects 

the difficulty inspecting units deployed in the underground coal mine environment. Units can become encrusted 
8

 

 

with dirt, making a thorough inspection difficult. The test results and data analysis, therefore, include all units 

tested whether the units passed subsequent NIOSH laboratory visual inspection or not. Units that failed 

laboratory inspection are noted in the results.

Dräger Oxy K Plus 

All 87 Dräger SCSRs passed cursory inspection done by the mine, but after cleaning the SCSRs of coal dust at 

NIOSH, five respirators failed the manufacturer’s recommended visual inspection. This means that 94% (82 of 

87) of the Oxy K Plus SCSRs collected passed visual inspection at NIOSH. Of the five units that failed inspection, 

three were missing the red plastic seals (Figure 7), and two had cracked moisture indicator windows (Figure 8). 

One of the cracked moisture indicators was also missing a circular band at its edge.

 Figure 7. Areas of Visual Inspection Deficiency

 

Circular band

New Indicator Window Cracked Indicator Window

Figure 8. New Moisture Indicator and Cracked Indicator Found After Cleaning 

at NIOSH
9

 

 

Ocenco EBA 6.5

Of the 103 Ocenco EBA 6.5 SCSRs that NIOSH collected, 19 failed the manufacturer’s recommended visual 

inspection criteria at NIOSH. The failures include outer cases cracked at the handle strap location (Figure 9), 

shifted cylinder bands with loose nuts, washers and/or brackets, scratched out serial numbers, crimped 

breathing hoses, and other signs of abuse (i.e., scuffs and hammer marks). NIOSH found one unit that passed the 

manufacturer’s recommended visual inspection to have a cracked cap nut on the demand valve. All of these 

defects indicate that the SCSRs were exposed to excessive force through impact during mine deployment. This 

means that 82% of the EBA 6.5 SCSRs collected passed visual inspection at NIOSH.

 Figure 9. Ocenco EBA 6.5 with Case Crack

Ocenco M-20

Of the 61 Ocenco M-20 SCSRs that NIOSH collected, 10 failed the manufacturer’s recommended visual 

inspection criteria at NIOSH. The failures include a missing ball in the yellow security latch, loose and missing 

bottom bumpers on the case, coal dust or a white powder inside in the case, gashes, and visible cracks in the top 

lid (Figures 10 and 11). After opening the SCSR with the cracked lid, researchers found dirt within the case. This 

means that 84% (51 of 61) of the M-20 SCSRs collected passed visual inspection at NIOSH.

Crack

Figure 10. Ocenco M-20 with Cracks in Top Lid
10

 

 

Figure 11. Ocenco M-20 Security Latch

Out of 252 SCSRs collected by NIOSH, 34 SCSRs (13%) failed visual inspection when applying the manufacturer’s 

criteria at NIOSH.

Quantitative Leak Test 

All units, regardless of whether or not the units passed the NIOSH laboratory visual inspection, were leak tested.

Dräger Oxy K Plus 

After checking the breathing circuit integrity of the Dräger Oxy K Plus SCSRs using the quantitative leak test 

(QLT), 99% (86 of 87) of the units had a leak rate less than 500 mL/min.

Ocenco EBA 6.5

When NIOSH performed the QLT to assess breathing circuit integrity, 85% of the EBA 6.5 SCSRs (87 out of 103) 

had a leak rate of less than 500 mL/min. Sixteen units had leakage rates greater than or equal to 500 mL/min,

possibly at the juncture of the plastic valve frame and the mouthpiece or due to leakage through the relief valve 

(Figures 12 and 13). These units were included in the BMS testing and found to meet the duration requirement. 
11

 

 

Figure 12. Ocenco EBA 6.5 Junction of Plastic Valves at Mouthpiece

Figure 13. Ocenco EBA 6.5 Relief Valve on Breathing Bag

Ocenco M-20

When NIOSH evaluated the breathing circuit integrity using the QLT, all 61 of the Ocenco M-20 respirators had 

leakages <500 mL/min. 
12

 

 

Gas Flow Test

Ocenco EBA 6.5

After testing the oxygen regulator flow rates, the average ranged from 1.63-2.15 liters per minute (L/min) at 

ambient temperature and pressure. Certification tests require a minimum constant flow of 1.5 L/min; therefore, 

all 103 Ocenco EBA 6.5 respirators passed the oxygen flow test. 

Breathing and Metabolic Simulation (BMS) Test

From the 251 collected SCSRs (not counting the 64 CSE SR-100 units), all units qualified for testing with the BMS: 

87 Dräger Oxy-K Plus, 103 Ocenco EBA 6.5, and 61 Ocenco M-20 respirators (Figure 14). When LTR1 collection 

and testing began in May of 2009, NIOSH decided to test all respirators that the mines and MSHA District Offices 

deemed as passing visual inspection. 

Figure 14. Dispersion of Respirators Qualified for BMS Testing

Dräger Oxy K Plus 

Of the 87 Dräger Oxy K Plus SCSRs that NIOSH tested on the BMS, there were two units which exceeded the 

maximum average inhaled CO2 requirement of 1.5% during the rated service life. These results were only 

slightly above 1.5% (1.7% and 1.9%, see Figure 16). These levels did not exceed the 4% inspired CO2

breakthrough level which could cause impairment. Overall, 99% of the respirators that passed visual inspection 

at NIOSH also passed BMS testing. Eighty percent (80%) of the respirators that failed visual inspection also 

passed BMS testing. The average duration time for the BMS testing was 85.4 minutes. All of the Dräger Oxy K 

Plus SCSRs passed the wet bulb, peak breathing pressure, and inhaled O2 performance requirements. The 

following BMS performance test results are graphically provided in Appendix A: 

• Duration of Dräger Oxy K SCSR (Figure 15)

• Average Percent Inspired CO2 of Dräger Oxy K SCSR (Figure 16)
13

 

 

• Average Percent Inspired O2 of Dräger Oxy K SCSR (Figure 17)

• Average Dry/Wet Bulb Temperature of Dräger Oxy K SCSR (Figure 18)

• Average Peak Inspired Pressure of Dräger Oxy K SCSR (Figure 19)

• Average Peak Expired Pressure of Dräger Oxy K SCSR (Figure 20)

Ocenco EBA 6.5

Of the 103 Ocenco EBA 6.5 SCSRs that NIOSH tested on the BMS, there were no failures during the 60 minute 

rated service life. There were 19 SCSRs that failed visual inspection, but each unit passed the BMS testing. The 

average duration time was 99.5 minutes. On one unit, the damaged cap nut caused oxygen to leak upon opening 

the cylinder valve which resulted in a shorter duration time of 70 minutes than the average BMS test time. The 

following BMS performance test results are graphically provided in Appendix B: 

• Duration of Ocenco EBA 6.5 SCSR (Figure 21)

• Average Percent Inspired CO2 of Ocenco EBA 6.5 SCSR (Figure 22)

• Average Percent Inspired O2 of Ocenco EBA 6.5 SCSR (Figure 23)

• Average Dry/Wet Bulb Temperature of Ocenco EBA 6.5 SCSR (Figure 24)

• Average Peak Inspired Pressure of Ocenco EBA 6.5 SCSR (Figure 25)

• Average Peak Expired Pressure of Ocenco EBA 6.5 SCSR (Figure 26)

Ocenco M-20

Of the 61 Ocenco M-20 SCSRs that NIOSH tested on the BMS, there was one failure during the 10 minute rated 

service life. This unit had an average inhaled CO2 of 2.0% but had a duration time of 14 minutes. Overall, 98% of 

the respirators that passed visual inspection at NIOSH also passed BMS testing. The average duration time for 

the BMS testing was 17.6 minutes. All of the Ocenco M-20 SCSRs passed the wet bulb, peak breathing pressure,

and inhaled O2 performance requirements. The following BMS performance test results are graphically provided 

in Appendix C: 

• Duration of Ocenco M-20 SCSR (Figure 27)

• Average Percent Inspired CO2 of Ocenco M-20 SCSR (Figure 28)

• Average Percent Inspired O2 of Ocenco M-20 SCSR (Figure 29)

• Average Dry/Wet Bulb Temperature of Ocenco M-20 SCSR (Figure 30)

• Average Peak Inspired Pressure of Ocenco M-20 SCSR (Figure 31)

• Average Peak Expired Pressure of Ocenco M-20 SCSR (Figure 32)

Test Data Summary

Table 3 is a summary of the results for the SCSR models. 

Table 3. Test Summary for SCSRs Passing Visual Inspection at the Mine and MSHA District Office

SCSR Models Dräger

OXY K Plus

Ocenco

EBA 6.5

Ocenco

M-20 Total

Units tested on BMS 87 103 61 251

Met rated service life on BMS 85 103 60 248

Did not meet rated service life on BMS 2 0 1 3
14

 

 

Failed visual inspection at NIOSH 5 19 10 34

Failed visual inspection at NIOSH, and did not met 

rated service on BMS 1 0 0 1

Failed visual inspection at NIOSH, but met rated 

service on BMS 4 19 10 33

Did not meet breathing circuit integrity requirement 1 16 0 17

Did not meet oxygen flow test requirement N/A 0 N/A 0

Conclusions 

All but three of the Ocenco and Dräger SCSRs tested on the BMS demonstrated an acceptable rated service life.

Of the three with unacceptable service lives, only one failed visual inspection. Overall, about 85% of the SCSRs 

examined at NIOSH passed visual inspection as well. There were no discernible trends from BMS, leak tests, or 

flow tests that might indicate or predict an end of service life for any SCSR model. Most of the respirators failing 

visible inspection in this phase of the study would have met the BMS testing criteria or been removed from 

service, if the manufacturer recommended cleaning, handling, and visual inspection had been performed 

properly. A loose chemical bed or lack of starter oxygen can be the product of rough handling, missed 

inspection, or a manufacturing defect. A proper visual inspection of a cleaned respirator case and indicators 

could have identified respirators that required removal from service. These preventative measures along with 

following the manufacturer’s prescribed 90 day and periodic service can identify respirators that have reached 

the end-of-service-life in the mining environment. 

The most frequent limitations in the collection of SCSRs from the mines could be partially overcome through 

better communication with the mines and district offices, and by obtaining a more recent and expanded 

inventory list from the MSHA electronic SCSR inventory. This phase of the LTR1 study demonstrated the need to 

expand collection options to meet the quota of 100 SCSRs from each manufacturer, and ultimately retain the 

desired statistical validity of the study.
15

 

 

Appendix A: Acronyms and Abbreviations 

Acronyms and Abbreviations

ASM

BMS

CO

CO2

CPIP

LTFE

LTR

MSHA

NIOSH

NPPTL

O2

OSHA

QLT

SCSR

TLV

VCO2

VO2

Acoustic Solid Movement

Breathing and Metabolic Simulation

Carbon Monoxide

Carbon Dioxide

Certified Product Investigation Process

Long-Term Field Evaluation

Long-Term Random Field Evaluation

Mine Safety and Health Administration

National Institute for Occupational Safety and Health 

National Personal Protective Technology Laboratory

Oxygen

Occupational Safety and Health Administration

Quantitative Leak Test

Self-Contained Self-Rescuer

Threshold Limit Value

Volume of Carbon Dioxide

Volume of Oxygen

Unit of Measure Abbreviations 

breaths/min

dB

kg

L

L/breath

lb

L/min

mL/min

mm

mm H2O

%

ppm

breaths per minute

decibel(s)

kilogram(s)

liter(s)

liter(s) per breath

pound(s)

liter(s) per minute

milliliter(s) per minute

millimeter(s)

millimeter(s) of water pressure

percent

parts per million
16

 

 

Appendix B: BMS Testing of the Dräger OXY K PLUS SCSRs Stressors 

Figure 15. Average Duration of Dräger Oxy K Plus SCSRs

Figure 16. Average Percent Carbon Dioxide of Dräger Oxy K Plus SCSRs
17

 

 

Figure 17. Average Percent Oxygen of Dräger Oxy K Plus SCSRs

Figure 18. Average Dry Bulb/Wet Bulb Temperature of Dräger Oxy K Plus SCSRs
18

Figure 19. Average Peak Inspired Pressure of Dräger Oxy K SCSR

Figure 20. Average Peak Expired Pressure of Dräger Oxy Plus K SCSR
19

 

 

Appendix C: BMS Testing of the Ocenco EBA 6.5 SCSRs Stressors

Figure 21. Average Duration of Ocenco EBA 6.5 SCSR

Figure 22. Average Percent Carbon Dioxide of Ocenco EBA 6.5 SCSR
20

 

 

Figure 23. Average Percent Oxygen of Ocenco EBA 6.5 SCSR

Figure 24. Average Dry/Wet Bulb Temperature of Ocenco EBA 6.5 SCSR
21

 

 

Figure 25. Average Peak Inspired Pressure of Ocenco EBA 6.5 SCSR

Figure 26. Average Peak Expired Pressure of Ocenco EBA 6.5 SCSR
22

 

 

Appendix D: BMS Testing of the Ocenco M-20 SCSRs Stressors

Figure 27. Average Duration of Ocenco M-20 SCSR

Figure 28. Average Percent Carbon Dioxide of Ocenco M-20 SCSR
23

 

 

Figure 29. Average Percent Oxygen of Ocenco M-20 SCSR

Figure 30. Average Dry/Wet Bulb Temperature of Ocenco M-20 SCSR

30

32

34

36

38

40

42

44

0 10 20 30 40 50 60

Average Dry/Wet Bulb Temperatures, oC

Sample Number

Dry Bulb Wet Bulb
24

 

 

Figure 31. Average Peak Inspired Pressure of Ocenco M-20 SCSR

Figure 32. Average Peak Expired Pressure of Ocenco M-20 SCSRs
25

 

 

Acknowledgements 

Thanks are extended to: MSHA, UMWA, Mine Operators, Self-Contained Self-Rescuer Manufacturers, Mine 

Workers, and NIOSH personnel that supported and continue to support the long-term field evaluation of SCSRs 

in U.S. underground coal mines. The authors gratefully acknowledge Courtney Neiderhiser2

, Nicholas Kyriazi2, 

and John P. Shubilla2who developed the initial draft of this document and for their contributions on the LongTerm Field Evaluation Project that include developing the sampling strategy, arranging the collection from the 

various mines, and testing of SCSRs. 

The following additional NIOSH National Personal Protective Technology Laboratory personnel are 

acknowledged for their contributions in providing assistance with developing this report: 

Gary Walbert, William D. Monaghan, and Michael Dojcak who compiled, reviewed, and analyzed the original 

LTR1 test data.

Judi Coyne, Marisa Fries, and Jordan Moore for their editorial support.

All photos courtesy of NIOSH NPPTL. 

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27

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Suggested Citation

NIOSH [2017]. PPE CASE: point-of-use assessment for self-contained self-rescuers randomly sampled from mining districts: 

first phase. By Coffey C, Murray D, Palya F. Pittsburgh PA: U.S. Department of Health and Human Services, Centers for 

Disease Control and Prevention, National Institute for Occupational Safety and Health, NPPTL Report Number P2018-0101.