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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-0105A Revision: 1.2 Date: 9 June 2021

DETERMINATION OF AIRFLOW - DEMAND AND PRESSURE-DEMAND,

TYPE C AND CE, SUPPLIED-AIR RESPIRATORS

STANDARD TESTING PROCEDURE (STP)

1. PURPOSE

This test establishes the procedures for ensuring that the air flow requirements on Type C and CE,

Demand and Pressure-Demand, Supplied-Air Respirators 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 J, Section 84.150, Table 8.

2. GENERAL

This STP describes the Determination of Airflow - Demand and Pressure-Demand, Type C and

CE Supplied-Air Respirators 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. A 300 cubic foot gas cylinder of compressed air or equivalent. (see Figure 1)

3.1.2. A Helicoid calibrated pressure gauge and connecting fittings or equivalent. (see 

Figure 1)

3.1.3. Air regulator, Model 8, from Matheson Gas Products or equivalent. (see Figure 

1)

3.1.4. National Instruments NI USB-9215A Portable USB-Based DAQ with 

Simultaneous Sampling; LabVIEW 2013; Dell Optiplex 755 Personal Computer, 

SCBA test software

3.1.5. 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

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

air flows - Model SR-085 or equivalent. 

3.1.7. Validyne Engineering model DP45-20 transducer used with Validyne 

Engineering model CD-19A carrier demodulator mounted in the Validyne MC1-

333 module case. Pressure range up to 3.5 inches of water - accuracy: ± 0.5% 
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Procedure No. RCT-ASR-STP-0105A Revision: 1.2 Date: 9 June 2021 Page 2 of 8 

F.S.

3.1.8. 3-Liter lung in bottle with plastic tubing, Hans Rudolph Co. part number CM 

1435 or equivalent. 

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

Company) or equivalent

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

Indiana or Setra Datum 2000 Model 239 digital manometer – accuracy: ± 

0.01%R ± 1 digit, or equivalent.

4. TESTING REQUIREMENTS AND CONDITIONS

4.1. Prior to beginning any testing, confirm that 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 traceable to recognized international standards when available. 

5. PROCEDURE

5.1. Perform pre-test balancing of transducer and recording system.

5.1.1. Connect the transducer to be used during testing in parallel with a manometer. 

Attach the manometer and transducer to a pressure regulated air supply. A pinch 

clamp, used for slight pressure changes, is placed in-line with two equal lengths 

of tubing for the manometer and transducer connections. An alternate method to 

generate low pressures for calibration is to use the Dwyer model A-396A 

calibration pump or equivalent.

5.1.2. Connect the transducer cable to the CD-19A demodulator, and then connect the 

demodulator to the National Instruments DAQ. The DAQ is then connected to 

the PC via USB port. Turn the system on and press the Calibration button. After 

the calibration screen appears, with no load applied to the transducer, press the 

Zero button to set the zero-pressure point.

5.1.3. Apply a pressure of 0.5 inches of water to the transducer/manometer system. 

Check that the demodulator reads 0.5 inches and adjust if necessary. Then check 

that the waveform displayed is at 0.5 inches and adjust the LabVIEW readout if 

necessary.

5.1.4. Repeat step 5.1.3 with the pressures of 1.0, 1.5, and 2.0 inches of water until each 

pressure point reads correctly on the waveform. No adjustments should be 

necessary at this point.

5.1.5. Verify that the pressures are correct, by applying pressure at 1.5, 0.5, and 0.0 

inches of water in descending order ensuring each pressure point reads correctly 

on the waveform. If adjustments are necessary, then repeat the calibration 
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Procedure No. RCT-ASR-STP-0105A Revision: 1.2 Date: 9 June 2021 Page 3 of 8 

process for all pressures.

5.1.6. After the calibration sequence is complete, remove the pressure source from the 

system.

5.2. Take precautions to mount the pressure transducer in a manner that isolates it from shock 

and vibration, in particular, that which is induced by the breathing machine and the 

operation of the SCBA.

5.3. Calibrate the breathing machine to 24 rpm with a stopwatch which gives 40 lpm. The 

breathing machine contains a cycle counter for obtaining exact and total cycle counts and 

is used to make precise corrections at end of test.

5.4. Mount facepiece on anthropometric head, taking care not to block resistance port below 

and left of nose, particularly if a nosecup is used. 

5.5. Connect the anthropometric head to the breathing machine. (see Figure 1.)

5.6. Mount the pressure transducer where shock and vibration are minimal. Secure the 

transducer to a ring stand and connect the transducer to the recorder. (see Figure 1.)

5.7. Attach breathing tube from facepiece to the air regulating valve, control valve, or orifice. 

The maximum length of air supply hose is attached to a cylinder of respirable air by way 

of a "T" with gauge and air regulator and the other end to the air regulating valve, control 

valve, or orifice.

5.8. Adjust the regulator until the desired pressure is reached using the minimum pressure 

with the maximum hose length and the maximum pressure with the minimum hose 

length.

5.9. Start the breathing machine and turn on the LabVIEW recorder. Run the breathing 

machine a minimum of 3 cycles for each hose length and pressure range requested by the 

manufacturer.

5.10. Data Analysis

5.10.1. The peak valves of the inhalation tracings shall remain positive with respect to 

the base-line (zero) established at the time the LabView system is calibrated. 

5.10.2. The breathing machine cam has a peak flow rate of 115 lpm; therefore, if the 

indication portion of the breathing curve remains positive, the flow is greater 

than 115 lpm.

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

required (42 CFR, Part 84, Section 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 J, Section 

84.150, Table 8.
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Procedure No. RCT-ASR-STP-0105A Revision: 1.2 Date: 9 June 2021 Page 4 of 8 

84.150 Air-supply line tests; minimum requirements.

Air supply lines employed on Types C and CE supplied-air respirators shall meet the 

minimum test requirements set forth in Table 8 of this subpart.

The air-supply hose, detachable couplings, and demand valve of the demand class or 

pressure-demand valve of the pressure-demand class for Type C supplied-air respirators, 

demand and pressure-demand classes, shall be capable of delivering respirable air at a 

rate of not less than 115 liters (4-cubic feet) per minute to the respiratory-inlet covering 

at an inhalation resistance not exceeding 50 millimeters (2 inches) of water column 

height measured in the respiratory-inlet covering with any combination of air-supply 

pressure and length of hose within the applicant's specified range of pressure and length 

of hose. The air-flow rate and resistance to inhalation shall be measured while the 

demand or pressure-demand valve is actuated 24 times per minute by a source of 

intermittent suction. The maximum rate of flow to the respiratory-inlet covering shall not 

exceed 425 liters (15 cubic feet) per minute under the specified operating conditions.

7. RECORDS\TEST SHEETS

7.1. All test data will be recorded on the AIRFLOW - DEMAND AND PRESSUREDEMAND, TYPE C AND CE, SUPPLIED-AIR RESPIRATORS test data sheet.

8. FIGURES

8.1. Flow Rate Determination Breathing Machine Set-up. (Figure 1.)
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Procedure No. RCT-ASR-STP-0105A Revision: 1.2 Date: 9 June 2021 Page 7 of 8 

Figure 1: Flow Rate Determination Breathing Machine Set-up
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Procedure No. RCT-ASR-STP-0105A Revision: 1.2 Date: 9 June 2021 Page 8 of 8 

Revision History

Revision Date Reason for Revision

1.0 2 July 2001 Historic document

1.1 27 September 2005 Update header and format to reflect lab move from Morgantown, 

WV. No changes to method

1.2 9 June 2021 Updated NIOSH Logo. Updated test procedure and figures to 

reflect new PC based recording system using LabVIEW, and other 

procedural changes related to calibration.