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-0127 Revision: 1.1 Date: 20 September 2005

DETERMINATION OF BY-PASS VALVE FLOW TEST - CLOSED-CIRCUIT, DEMAND AND 

PRESSURE-DEMAND, SELF-CONTAINED BREATHING APPARATUS 

STANDARD TESTING PROCEDURE (STP) 

1. PURPOSE

This test establishes the procedures for ensuring that the level of protection provided by the bypass valve flow requirements on Closed-Circuit, Self-Contained Breathing Apparatus (SCBA) 

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 By-Pass Valve Flow Test for Closed-Circuit SCBA 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. ISI Anthropometric Test heads with tube for measuring breathing resistance and 

air flows - Model SR-085 or equivalent.

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Procedure No. RCT-ASR-STP-0127 Revision: 1.1 Date: 20 September 2005 Page 2 of 8 

3.1.2. Electric timer, calibrated to hundredths of a minute (Precision Scientific 

Company) or equivalent. 

3.1.3. Singer Dry Test Meter (Model 806) one cubic foot per revolution 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. 

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 

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Procedure No. RCT-ASR-STP-0127 Revision: 1.1 Date: 20 September 2005 Page 3 of 8 

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

5.1. Fully pressurize the oxygen cylinder to service pressure of the respirator. 

5.2. Mount the facepiece on an anthropometric head form. Connect a dry test meter to the 

outlet port at the rear of the head form. 

5.3. Use the tool provided by the manufacturer to override the relief valve. 

5.4. Open by-pass valve fully. 

5.5. Open cylinder valve and simultaneously start timer. 

5.6. When cylinder is down to 500 psig stop timer and turn off cylinder valve. 

5.7. Record number of revolutions on dry test meter and time on timer on test data sheet. 

5.8. Refer to data analysis. 

5.9. Data Analysis 

One revolution on dry test meter is equal to 28.32 liters per minute. Take number of 

revolutions recorded in Step 5.7 and multiply by 28.32. Divide this number by the time 

also recorded in Step 5.7. 

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: 

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 

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Procedure No. RCT-ASR-STP-0127 Revision: 1.1 Date: 20 September 2005 Page 4 of 8 

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

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

6.3. All by-pass valves for closed circuit SCBA shall deliver a minimum average flow rate of 

30 lpm in the fully open position from full service pressure down to and including 500 

psig. 

7. RECORDS\TEST SHEETS

7.1. All test data will be recorded on the SPECIAL TEST - BY-PASS FLOW - CLOSEDCIRCUIT, SELF-CONTAINED BREATHING APPARATUS test data sheets. 

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. 

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-SOP0005-00. 

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Procedure No. RCT-ASR-STP-0127 Revision: 1.1 Date: 20 September 2005 Page 5 of 8 

SPECIAL TEST - BY-PASS FLOW - CLOSED-CIRCUIT, 

SELF-CONTAINED BREATHING APPARATUS

Project No. : Date: __________ 

Company : ______________________________________________ 

Respirator Type : ______________________________________________ 

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

Requirement: All by-pass valves for closed circuit SCBA shall deliver a minimum flow rate of 30 lpm 

in the full open position when tested from full cylinder pressure down to 500 psig. 

Results: 

Unit #1 - _______________ 

Unit #2 - _______________ 

Comments : 

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________ 

Test Engineer: PASS FAIL________ 

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Procedure No. RCT-ASR-STP-0127 Revision: 1.1 Date: 20 September 2005 Page 7 of 8 

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Procedure No. RCT-ASR-STP-0127 Revision: 1.1 Date: 20 September 2005 Page 8 of 8 

Revision History 

Revision Date Reason for Revision 

1.0 13 November 

2000 

Historic document 

1.1 20 September 

2005 

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

No changes to method 

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