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-0137 Revision: 1.1 Date: 27 September 2005

DETERMINATION OF CONTINUOUS GAS FLOW ON CONSTANT FLOW WITH DEMAND, 

CLOSED-CIRCUIT, 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 gas 

flow requirements on Constant Flow with Demand, 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), and Subpart H, Section 84.94(b); Volume 60, Number 110, June 8, 

1995. 

2. GENERAL

This STP describes the Determination of Continuous Gas Flow on Constant Flow with Demand, 

Closed-Circuit, Self-Contained 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. Electric Timer, calibrated to hundredths of a minute (Precision Scientific 

Company) or equivalent.

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Procedure No. RCT-ASR-STP-0137 Revision: 1.1 Date: 27 September 2005 Page 2 of 13 

3.1.2. Dry test - Gas meter, (Singer-American Meter Division - Model DTM-200A) or 

equivalent. 

3.1.3. Wet Test - Gas Meter (Singer-American Meter Company - Model AL17-1) 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 at all times. 

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

5.1. The regulator or constant flow outlet is connected to a calibrated wet test meter (traceable 

to NIST using Dry Test Gas Meter). 

5.2. Flow readings are recorded initially and every 10 minutes for the rated service time of the 

unit. The last 10 minutes are monitored every other minute. 

5.3. Data Analysis 

Record flow readings directly from the wet test gas meter. 

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), and Subpart H, Section 84.94(b); 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 

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

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

84.94 Gas flow test; closed-circuit apparatus. 

(b) Where constant flow is used in conjunction with demand flow, the constant flow shall 

be greater than 1.5 liters per minute for the entire rated service time. 

7. RECORDS\TEST SHEETS

7.1. All test data will be recorded on the GAS FLOW TEST, CONSTANT FLOW WITH 

DEMAND, CLOSED-CIRCUIT, SELF-CONTAINED BREATHING APPARATUS test 

data sheet. 

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Procedure No. RCT-ASR-STP-0137 Revision: 1.1 Date: 27 September 2005 Page 4 of 13 

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

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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GAS FLOW TEST, CONSTANT FLOW WITH DEMAND, CLOSED-CIRCUIT, 

SELF-CONTAINED BREATHING APPARATUS

Project No. : Date: __________ 

Company : ____________________________________________ 

Respirator Type : ____________________________________________ 

Reference: 42 CFR 84, Subpart H, Section 84.94(b). 

Requirement: Where constant flow is used in conjunction with demand flow, the constant flow shall be 

1.5 1pm for entire rated service time of unit. 

Results: 

 Unit #1 Time/Min. Flow/LPM Unit #2 Time/Min. Flow/LPM

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Test Engineer: PASS FAIL________ 

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Revision History 

Revision Date Reason for Revision 

1.0 24 May 2001 Historic document 

1.1 27 September 

2005 

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

No changes to method 

 

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