Approvals: 1st Level 2nd Level 3rd Level 

National Institute for Occupational Safety and Health 

National Personal Protective Technology Laboratory 

P.O. Box 18070 

Pittsburgh, PA 15236 

Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005

DETERMINATION OF DIAPHRAGM OVER PRESSURIZATION 

ON OPEN-CIRCUIT, SELF-CONTAINED BREATHING APPARATUS 

WITH BELT MOUNTED REGULATORS AND BREATHING TUBES 

STANDARD TESTING PROCEDURE (STP) 

1. PURPOSE

This test establishes the procedures for ensuring that the level of protection provided by the 

diaphragm over pressurization requirements on Open-Circuit, Self-Contained Breathing 

Apparatus (SCBA) with a belt mounted second stage regulator and a flexible breathing tube 

connected to the facepiece, submitted for Approval, Extension of Approval, or examined during 

Certified Product Audits, meet the minimum certification standards set forth in 42 CFR, Part 84, 

Subpart G, Section 84.63(a)(c)(d), Volume 60, Number 110, June 8, 1995. 

2. GENERAL

This STP describes the Determination of Diaphragm Over Pressurization on Open-Circuit, SelfContained Breathing Apparatus test in sufficient detail that a person knowledgeable in the 

appropriate technical field can select equipment with the necessary resolution, conduct the test, 

and determine whether or not the product passes the test. 

3. EQUIPMENT/MATERIALS

3.1. The list of necessary test equipment and materials follows: 

3.1.1. Two channel thermal tip recording system (Gould Model No. RS3200) with 

carrier amplifier (Model No. 13-4615-35) or equivalent.

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3.1.2. Mechanical Breather with 622 Kg.m/min. Cam as per U.S. BOM Drawings C1748 (3/17/69) Breathing Machine and B-1198 (3/6/69) Breathing Cam or 

equivalent. 

3.1.3. ISI Anthropometric Test heads with tube for measuring breathing resistance and 

air flows - Model SR-085 or equivalent. 

3.1.4. Temperature compensated pressure transducer (Validyne Engineering Model No. 

DP45) or equivalent. 

3.1.5. Electric Timer, calibrated to hundredths of a minute (Precision Scientific 

Company) or equivalent. 

3.1.6. Skinner Electronic Valve No. LC2DA 4l50, l50 PSI, 8 watts, l20/60 volts, New 

Britain, Conn. or equivalent. 

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3.1.7. Helicoid Standard Gauge + l/2% or equivalent. 

3.1.8. NaCl Generator and Penetrometer - Frontier Enterprises Model FE560A NaCl 

aerosol test system or equivalent. 

3.1.9. Two stage pressure reducer - Matheson or equivalent. 

3.1.10. A 300 cubic foot gas cylinder of compressed air or equivalent. 

3.1.11. N.P.T. Piping 

3.1.12. Hose Clamps 

3.1.13. Pneumatic (BOM) - Drawing PR-0011-13 (9/16/69) or equivalent. 

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3.1.14. Multiple outlet box with 6 receptacles or equivalent. 

3.1.15. Corn Oil Generator and Chamber - Dynatech Frontier Enterprises Model 260 - 

(May be substituted for No. 3.1.8., above) or equivalent. 

3.1.16. Teledyne Hastings - Ray Dist Mass Flow Meter - Model NAHL-25 (May be 

substituted for No. 3.1.13., above) or equivalent. 

4. TESTING REQUIREMENTS AND CONDITIONS

4.1. Prior to beginning any testing, all measuring equipment to be used must have been 

calibrated in accordance with the manufacturer's calibration procedure and schedule. At 

a minimum, all measuring equipment utilized for this testing must have been calibrated 

within the preceding 12 months using a method traceable to the National Institute of 

Standards and Technology (NIST). 

4.2. The compressed gas cylinder must meet all applicable Department of Transportation 

requirements for cylinder approval as well as for retesting/requalification. 

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4.3. Normal laboratory safety practices must be observed. This includes all safety precautions 

described in the current ALOSH Facility Laboratory Safety Manual. 

4.3.1. Safety glasses, lab coats, and hard-toe shoes must be worn during all testing. 

4.3.2. Work benches must be maintained free of clutter and non-essential test 

equipment. 

4.3.3. When handling any glass laboratory equipment, lab technicians and personnel 

must wear special gloves which protect against lacerations or punctures. 

5. PROCEDURE

Note: Reference Section 3 for equipment, model numbers and manufacturers. For calibration 

purposes use those described in the manufacturer’s operation and maintenance manuals. 

5.1. REGULATOR DIAPHRAGM INTEGRITY TEST

Abstract - Regulators to be tested are assembled with diaphragm and retainers (where required) 

and leak tested by the manufacturers' QA test procedure, mounted in the NaCl challenge aerosol 

test chamber and initial penetration noted. Regulator is then tested for resistance to over 

pressurization for l00 cycles at moderate and l0 cycles at high air flows, retested for penetration 

and for leakage. Criteria for rejection of the regulator are: 

5.1.1. Damage or permanent deformation in any component; or 

5.1.2. Visible damage or breach of the diaphragm, including bubbles, thinning 

stretching; or 

5.1.3. Average NaCl penetration greater than 0.002%; or 

5.1.4. Failure of any Subpart H test. 

5.2. Test Protocol

Four regulators will be tested as received from the manufacturer. All four regulators 

must successfully complete the regulator test series (tests l-4 above) before starting 

Subpart H testing. In addition, all units tested as complete assemblies must successfully 

complete all required Subpart H tests for approval or extension of approval. 

5.3. The general tests will consist of the following sequence:

5.3.1. NaCl penetration test of regulator before over pressurization. 

5.3.2. Diaphragm over pressurization test at a low flow simulating an escape with the 

bypass. 

5.3.3. Diaphragm over pressurization test at maximum flow simulating severe misuse 

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Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005 Page 6 of 13 

of the bypass without the facepiece attached. 

5.3.4. NaCl penetration test of the regulator after over pressurization. 

5.3.5. Visual and dimensional inspection. 

5.3.6. Approval tests for SCBA, Subpart H. 

*NOTE: WHEN USING CORN OIL THIS PROCEDURE REMAINS THE SAME. 

5.4. NaCl Penetration Test

5.4.1. Regulator is mounted on a ring stand in the center of a 3 feet in diameter by 3 

feet high double walled test hood. The regulator is supplied with breathing air by 

an externally mounted cylinder and is cycled by the standard breathing machine 

(l) through a special 6 feet breathing tube assembly attached to a facepiece and 

mounted on a test dummy attached to the breathing machine. 

5.4.2. The regulator is challenged with a NaCl aerosol of approximately 0.6 

micrometers MMAD at a concentration of approximately l5 milligram per cubic 

meter generated by a Frontier Enterprises model FE 560A NaCl aerosol test 

system. 

5.4.3 As the regulator in (5.4.3.1.) is cycled, air is sampled at approximately 0.3 liters 

per minute from the facepiece and passed through the Frontier flame photometer 

and the pulse height is recorded on a strip chart. The average of peak pulse 

heights for a 5 minute period is reported as average penetration. 

5.4.3.1. A breathing machine cam with a work rate of 622 kg-m/min. and 24 

respirations/min. with an approximate minute volume of 40 liters. 

5.4.4. Maximum allowable average penetration will be 0.002% which is the value 

reported for an undamaged regulator diaphragm. All four regulators must pass 

the penetration test. 

5.4.5. A similar test using DOP is available and has been used by some manufacturers 

for penetration studies. Test results seem comparable at low levels with NaCl but 

NIOSH tests will be performed with NaCl. 

5.5. Regulator Over Pressurization Test - See Figure l for test setup. 

5.5.1. The regulator, high-pressure hose assembly and variable pressure source of highpressure breathing air are connected to a pressure gage or pressure 

transducer/recorder, an electrically operated valve, and transducer/recorder, by 

the regulator outlet. 

5.5.2. The regulator by-pass valve is used to control the flow through the regulator, as 

measured by the transducer/recorder, out the electrically operated valve which is 

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Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005 Page 7 of 13 

used to interrupt the flow to over pressurize the regulator. The regulator over 

pressure is then recorded. 

5.5.3. Initial flow rate is 200 liters per minute with a source pressure of 20-25% of the 

maximum rated service pressure. 

5.5.4. Final flow rate is maximum deliverable by regulator at the maximum rated 

cylinder pressure. 

5.5.5. 100 cycles consisting of 1-2 second actuations of the valves with 1-2 second 

pause are performed at the lower flow rate. 

5.5.6. 10 similar cycles will be performed at the higher flow rate 

5.5.7. Damage or permanent deformation in any component or visible damage or 

breach to the diaphragm will be considered a failure and will be cause for 

rejection of the application. No adjustment or repair of the regulator is allowed 

before the penetration test. 

5.6. NaCl Penetration Test

Repeat this test. 

Failure of the regulator to pass the leak test before over pressurization will be cause for 

rejection of that regulator for rework and retesting. Failure of a second test will be cause 

for rejection of that regulator and substitution of another unit. 

5.7. Visual Inspection

All tested diaphragms and regulators will be visibly inspected at the completion of the 

penetration tests. No permanent damage or deformation to the components or visible 

damage or breach of the diaphragm, including bubbles or thinning or stretching, will be 

allowed. 

5.8. Subpart H Tests

Tests of complete SCBA's will be carried out in accordance with Subpart H on at least 

two units. 

Note: This test should be done on a minimum of two respirators, or more if additional testing is 

required (42 CFR, Part 84, Sections 84.12, 84.30, and 84.60.) 

6. PASS\FAIL CRITERIA

6.1. The criterion for passing this test is set forth in 42 CFR, Part 84, Subpart G, Section 

84.63(a)(c)(d), Volume 60, Number 110, June 8, 1995. 

6.2. This test establishes the standard procedure for ensuring that: 

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Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005 Page 8 of 13 

84.63 Test requirements; general. 

(a) Each respirator and respirator component shall when tested by the applicant and by 

the Institute, meet the applicable requirements set forth in subparts H through L of this 

part. 

(c) In addition to the minimum requirements set forth in subparts H through L of this 

part, the Institute reserves the right to require, as a further condition of approval, any 

additional requirements deemed necessary to establish the quality, effectiveness, and 

safety of any respirator used as protection against hazardous atmospheres. 

(d) Where it is determined after receipt of an application that additional requirements will 

be required for approval, the Institute will notify the applicant in writing of these 

additional requirements, and necessary examinations, inspections, or tests, stating 

generally the reasons for such requirements, examinations, inspections, or tests. 

6.3. Regulators to be tested are assembled with diaphragm and retainers (where required) and 

leak tested by the manufacturers' QA test procedure, mounted in the NaCl 

challenge aerosol test chamber and initial penetration noted. Regulator is then 

tested for resistance to over pressurization for l00 cycles at moderate and l0 

cycles at high air flows, retested for penetration and for leakage. Criteria for 

rejection of the regulator are: 

6.3.1. Damage or permanent deformation in any component; or 

6.3.2. Visible damage or breach of the diaphragm, including bubbles, thinning or 

stretching; or 

6.3.3. Average NaCl penetration greater than 0.002%; or 

6.3.4. Failure of any Subpart H test. 

7. RECORDS\TEST SHEETS

7.1. All test data will be recorded on the SPECIAL TEST - DIAPHRAGM OVER 

PRESSURIZATION, OPEN-CIRCUIT, SELF-CONTAINED BREATHING 

APPARATUS WITH BELT MOUNTED REGULATORS AND BREATHING TUBES 

test data sheet. 

7.2. All videotapes and photographs of the actual test being performed, or of the tested 

equipment shall be maintained in the task file as part of the permanent record. 

7.3. All equipment failing any portion of this test will be handled as follows; 

7.3.1. If the failure occurs on a new certification application, or extension of approval 

application, send a test report to the RCT Leader and prepare the hardware for 

return to the manufacturer. 

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Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005 Page 9 of 13 

7.3.2. If the failure occurs on hardware examined under an Off-the-Shelf Audit the 

hardware will be examined by a technician and the RCT Leader for cause. All 

equipment failing any portion of this test may be sent to the manufacturer for 

examination and then returned to NIOSH. However, the hardware tested shall be 

held at the testing laboratory until authorized for release by the RCT Leader, or 

his designee, following the standard operating procedures outlined in Procedure 

for Scheduling, and Processing Post-Certification Product Audits, RB-SOPUncontrolled Copy 

0005-00. 

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Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005 Page 10 of 13 

SPECIAL TEST - DIAPHRAGM OVER PRESSURIZATION, OPEN-CIRCUIT, 

SELF-CONTAINED BREATHING APPARATUS 

WITH BELT MOUNTED REGULATORS AND BREATHING TUBES

Project No : Date: __________ 

Company : ___________________________________________ 

Respirator Type: ___________________________________________ 

Reference: 42 CFR, Part 84, Subpart G, Section 84.63(a)(c)(d) 

Regulator Regulator No. Diaphragm No. Torque NaCl% Flow Rate Cycles NaCl% Visual Inspection Pass Fail

 Initial LPM Final 

1. ___________ ____________ _____ ______ 200 100 ______ _____________ ____ ____ 

 Max. 10 

2. ___________ ____________ _____ ______ 200 100 ______ _____________ ____ ____ 

 Max. 10 

3. ___________ ____________ _____ ______ 200 100 ______ _____________ ____ ____ 

 Max. 10 

4. ___________ ____________ _____ ______ 200 100 ______ _____________ ____ ____ 

 Max. 10 

 VISUAL INSPECTION NOTES 

Comments : 

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Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005 Page 11 of 13 

Data Analysis 

Regulator 1. Initial 2. Final 3. Unacceptable 4. Visible 

 No. NaC1 Penet. NaC1 Penet. Regulator or Breach in 

 Pass/Fail Pass/Fail Component Deformation Diaphragm

 I. ________ ________ ____________________ _________ 

 

 II. ________ ________ ____________________ _________ 

 

 III. ________ ________ ____________________ _________ 

 

 IV. ________ ________ ____________________ _________ 

 

 

Totals: ________ ________ ____________________ _________ 

Comments : 

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_____________________________________________________________________________________

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_____________________________________________________________________________________ 

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______________________________________________________________________________

Test Engineer: ___________________________________ Pass: ________ Fail: ________ 

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Figure 1 

Diaphragm Over Pressurization Test Setup Uncontrolled Copy 

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Procedure No. RCT-ASR-STP-0146 Revision: 1.1 Date: 12 September 2005 Page 13 of 13 

Revision History 

Revision Date Reason for Revision 

1.0 6 February 2001 Historic document 

1.1 12 September 

2005 

Update header and format to reflect lab move from Morgantown, WV 

No changes to method 

 

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