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National Institute for Occupational Safety and Health

National Personal Protective Technology Laboratory 

626 Cochrans Mill Road 

Pittsburgh, PA 15236

Procedure No. RCT-ASR-STP-0123 Revision: 1.2 Date: 13 May 2020

DETERMINATION OF GAS FLOW MEASUREMENTS - OPEN-CIRCUIT,

DEMAND AND PRESSURE-DEMAND, SELF-CONTAINED BREATHING APPARATUS

STANDARD TESTING PROCEDURE (STP)

1. PURPOSE

This test establishes the procedures for ensuring the gas flow requirements for an Open-Circuit,

Demand and Pressure-Demand, Self-Contained Breathing Apparatus (SCBA) meet the minimum

performance requirements set forth in 42 CFR, Part 84, Subpart H, Section 84.93.

2. GENERAL

This STP describes the Determination of Gas Flow Measurements - Open-Circuit, Demand and

Pressure-Demand, 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. ISI Anthropometric Test heads with tube for measuring breathing resistance and 

air flows - Model SR-085 or equivalent. 

3.1.2. Hastings Mass Flow meter Model AHL-25 (Teledyne Hastings - Raydist) or 

equivalent. 

3.1.3. Spencer Turbo Compressor (Catalog No. 075-1/3-Bushnell Machinery Co.) or 

equivalent. 

3.1.4. Dwyer series 477 AV Digital Manometer, accuracy +/- 0.5% FS or equivalent. 

3.1.5. High Pressure Test Stand. A test stand incorporating calibrated pressure gauges 

(one 0-10,000 psig and one 0-3,000 psig). 

3.1.6. Dwyer Slant Manometer 0-3", F. W. Dwyer Manufacturing Co., Michigan City, 

Indiana or equivalent. 

4. TESTING REQUIREMENTS AND CONDITIONS

4.1. Prior to beginning any testing, all measuring equipment employed has been calibrated in

accordance with the testing laboratory’s calibration procedure and schedule. All 

measuring equipment utilized for this testing must have been calibrated using a method 
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Procedure No. RCT-ASR-STP-0123 Revision: 1.2 Date: 13 May 2020 Page 2 of 6 

traceable to recognized international standards when available.

5. PROCEDURE

5.1. Assemble unit as per manufacturer's instructions with the facepiece mounted on an 

anthropometric head. 

5.2. Connect a mass flow meter in line between the anthropometric head and an adjustable 

vacuum source, keeping airflow path as straight as possible. 

5.3. Charge the test stand to a pressure equal to full cylinder pressure.

5.4. Connect the test stand in place of the cylinder.

5.5. Connect a pressure tap in the head to the slant manometer for determining facepiece 

pressure. 

5.6. The vacuum source is adjusted during the test to maintain zero pressure inside the 

facepiece for pressure-demand units and minus (-) two inches of water pressure for 

demand units. 

5.7. Flow measurements are taken directly from the mass flow meter.

5.8. Repeat the above procedure with the test stand charged to 500 psig. 

5.9. Record the readings. 

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 H, Section 

84.93. 

Reference: 84.93 Gas flow test; open-circuit apparatus.

(a) A static-flow test will be performed on all open-circuit apparatus. 

(b) The flow from the apparatus shall be greater than 200 liters per minute when the 

pressure in the facepiece of demand-apparatus is lowered by 51 mm. (2 inches) watercolumn height when full container pressure is applied. 

(c) Where pressure demand apparatus are tested, the flow will be measured at zero gage 

pressure in the facepiece.

(d) Where apparatus with compressed-breathing-gas containers are tested, the flow test 

shall also be made with 3,450 kN/m.2

 (500 psig.) container pressure applied. 
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Procedure No. RCT-ASR-STP-0123 Revision: 1.2 Date: 13 May 2020 Page 3 of 6 

7. RECORDS\TEST SHEETS

7.1. Record the test data in a format that shall be stored and retrievable. Data shall be 

reported as shown in attached example data sheet.

8. ATTACHMENTS

8.1. Sample Data Sheet

8.2. Photograph of Test Setup 
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Procedure No. RCT-ASR-STP-0123 Revision: 1.2 Date: 13 May 2020 Page 4 of 6 

8.1. Sample Data Sheet 
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Procedure No. RCT-ASR-STP-0123 Revision: 1.2 Date: 13 May 2020 Page 5 of 6 

8.2. Photograph of Test Setup 

Figure 1: Photo of the test setup
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Procedure No. RCT-ASR-STP-0123 Revision: 1.2 Date: 13 May 2020 Page 6 of 6 

Revision History

Revision Date Reason for Revision

1.0 23 August 2002 Historic document

1.1 21 September 2005 Update header and format to reflect lab move from Morgantown, 

WV. No changes to method

1.2 13 May 2020 Updated NIOSH Logo. Updated Sections 3, 4, 5, and 6, with 

changes related to equivalent equipment, outdated pictures 

(removed), calibration requirements, and the procedure.