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-APR-STP-0065 Revision: 1.1 Date: 12 September 2005

DETERMINATION OF AIR FLOW RESISTANCE OF 

BREATH RESPONSIVE, POWERED AIR-PURIFYING RESPIRATORS (PAPR’s) 

STANDARD TESTING PROCEDURE (STP) 

 

1. PURPOSE

 

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

responsive powered air-purifying respirators (PAPR’s) meets the requirements deemed as 

appropriate under 42 CFR 84.157 for air flow and breathing resistance. Breath responsive 

powered air-purifying respirators (PAPR’s) are designed to maintain a positive pressure in the 

facepiece in order to match the respiratory requirements of the user. The requirements for the 

evaluation of a PAPR under Part 84 do not address these design features. Therefore, in 

accordance with the applicable sections of 42 CFR § 84.60 and § 84.63, these types of PAPR’s 

will be evaluated under the requirements for PAPRs in 42 CFR Part 84 which are applicable to its 

design and under those additional requirements which NIOSH determines are necessary to ensure 

the quality, effectiveness and safety of the respirator. Since, there is no applicable test or 

requirements for a breath responsive respirator in the PAPR requirements, the airflow resistance 

of this device will be evaluated under the requirements of §84.157 for pressure-demand supplied 

air respirators which can adequately test the quality, effectiveness and safety of this type of 

design feature. These are as follows: 

 

84.157. Airflow resistance test; Type C supplied-air respirator, pressure-demand class; minimum 

requirements. 

(a) The static pressure in the facepiece shall not exceed 38 mm. 

(1.5 inches) of water-column height. 

 

 (b) The pressure in the facepiece shall not fall below atmospheric at inhalation 

airflows less that 115 liters (4 cubic feet) per minute.

(c) The exhalation resistance to a flow of air at a rate of 85 liters 

 (3 cubic feet) per minute shall not exceed the static pressure in the 

 facepiece by more than 51mm (2 inches) of water-column height.

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 2 of 10 

2. GENERAL

2.1. This STP describes the Determination of Breathing Resistance of Breath Responsive 

Powered Air-Purifying Respirators (PAPR’s) 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 (Model Number 1102B Hewlett 

Packard) with Carrier Preamplified (Number 8805A) or equivalent. 

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. 

3.1.3. Anthropometric test head with probe at upper lip for measuring breathing 

resistance (Sierra Engineering Company Model 428) or equivalent. 

3.1.4. Temperature compensated strain sensitive resistance wire type transducer 

(Stratham Instruments). Pressure rate + 0.5 psig 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-air 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. 

4.3. 42 CFR, Part 84, Subpart J, Section 84.156 and 84.157, Volume 60, Number 110, June 8, 

1995. 

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 3 of 10 

84.156 Air Flow resistance test; Type C supplied-air respirator, demand class; minium 

requirement. 

(a) Inhalation resistance shall not exceed 50 millimeters (2 inches) 

of water at an air flow of 115 liters (4 cubic feet) per minute. 

(b) The exhalation resistance to a flow of air at a rate of 85 liters (3 

cubic feet) per minute shall not exceed 25 millimeters (1 inch) of water. 

84.157 Air Flow resistance test; Type C supplied-air respirator, pressure-demand 

class; minimum requirements. 

(a) The static pressure in the facepiece shall not 

exceed 38 mm (1.5 inches) of water-column 

height. 

(b) The pressure in the facepiece shall not fall below 

atmospheric at inhalation airflows of 115 liters 

(4 cubic feet) per minute. 

5. PROCEDURE

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

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

5.1.1. Turn on recorder and allow at least 30-minute warmup. 

5.1.2. Assemble the apparatus as shown in Figure 1. Mount the pressure 

 transducer where shock and vibration are minimal. 

5.1.3. Assemble respirator and mount facepiece on anthropometric head, taking care 

not to block resistance port below and left of nose, particularly if a nosecup is 

used. Make sure that the face seal is leak tight by blocking off the inhalation port 

of the facepiece and inhaling through the breathing tube port exiting the back of 

head. After building up several inches of negative pressure hold breathing 

several seconds, which will enable you to determine if a leak is present. If there 

is a leak, readjust headstraps and facepiece position and repeat leak test until a 

seal is obtained. 

 

 5.1.4. Connect the breathing tube to facepiece. Do not connect head to breathing 

machine. Turn on breathing machine and use a timer to determine that the cam is 

operating at 24 rpm. (This will give a 40 lpm volume). When calibrated, turn 

breathing machine off. 

5.1.5. Zero the recorder base-lines to mid-point of chart paper. Calibrate the pressure 

transducer and balance the carrier preamplifier as instructed in the manual. 

5.1.6. Connect the anthropometric head to the breathing machine. 

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5.1.7. Turn on the blower unit with fully charged batteries. 

5.1.8. Turn on breathing machine for three complete cycles to obtain inhalation 

resistance. (See data Analysis, Appendix C.) Then turn off breathing machine 

leaving blower turned on. 

5.1.9. With the blower unit still turned on connect transducer port from head form to a 

slant manometer to obtain static pressure in facepiece. 

5.1.10. When tracings are complete shut off breathing machine and blower unit, 

disconnect transducer from head (make sure recorder speed and attenuator switch 

are both off). 

5.1.12. Retrieve the tracings on chart paper for data analysis. 

NOTE: This test should be done on a minimum of three respirators, or more if additional 

testing is required. 

 5.2. Data Analysis. Reference Appendix B. 

 5.2.1. Take the peak values of the inhalation tracings and read 

resistances in inches of water column height. 

 5.2.2. All values read in paragraph 1 may not exceed 50 mm (2 inches) of water 

column height in order to meet Part 84 performance requirements. 

 5.2.3. For pressure-demand units the inhalation resistance cannot fall below the 

zero pressure base line. A negative spike is allowed as long as there is 

no area between the point where the spike goes negative and the point 

where it returns to positive. 

 

 5.2.4. All values obtained in paragraph 5.1.9. of test procedure may not exceed 38 mm 

(1.5 inches) of water column height in order to meet Part 84 performance 

requirements. 

6. PASS\FAIL CRITERIA

6.1. The criterion for passing this test is set forth in Subpart J, Sections 84-157.

7. RECORDS\TEST SHEETS

7.1. All test data will be recorded on the Determination of Air Flow Resistance of Breath 

Responsive Powered Air-Purifying Respirators 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. 

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 5 of 10 

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

7.3.1. If the failure occurs on new certification application hardware, send a test report 

to the Team Leader and prepare the hardware for return to the manufacturer. 

7.3.2. If the failure occurs to hardware examined under an Extension of Approval or 

Off-the-Shelf Audit; the hardware will be examined by a technician and the 

Team Leader for cause. All equipment failing any portion of this test may be 

returned to the manufacturer applicant for examination. However, the hardware 

tested shall be held at the testing laboratory until authorized for release by the 

Team Leader, or his designee, following the standard operating procedures 

outlined in Procedure for Scheduling, and Processing Post-Certification Product 

Audits, RB-SOP-0005-00. 

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 6 of 10 

Appendix A 

Equipment Required 

1. Two channel thermal tip recording system (Model Number 1102B Hewlett 

Packard) with Carrier Preamplifier (Number 8805A) or equivalent. 

2. Mechanical breather with 622 Kg m/min. cam as per U.S. BOM Drawings Cl748 (3/l7/69) Breathing Machine and B-ll98 (3/6/69) Breathing Cam. 

3. Anthropometric test head with probe at upper lip for measuring breathing 

resistance (Sierra Engineering Company Model 428) or equivalent. 

4. Temperature compensated strain sensitive resistance wire type transducer 

(Stratham Instruments). Pressure range + 0.5 psig or equivalent. 

5. Dwyer slant manometer with a range of 1 to 3 inches of water or equivalent. 

 

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 7 of 10 

Appendix B 

 Test/Data Sheets 

1. Determination of Air Flow Resistance of Breath Responsive Powered AirUncontrolled Copy 

Purifying Respirators Test Data Sheet. Uncontrolled Copy 

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 8 of 10 

AIR FLOW RESISTANCE 

 BREATH RESPONSIVE POWERED AIR-PURIFYING RESPIRATORS (PAPR’s)

Date: _____________ 

Project No.: 

Company: 

Respirator Type: 

42 CFR Part 84 Reference: 42 CFR 84.60 & 84.63, Subpart J 84.157 

Pressure- Demand Class SAR. 

 Requirement: (a) Inhalation resistance shall not exceed 50 mm 

(2 inches) of H2O column height at an airflow 

of 115 lpm. (4 cfm). 

 (b) The exhalation resistance to a flow of air at a 

rate of 85 lpm. (3 cfm.) shall not exceed 

25 mm (1 inch) of H2O column height. 

Results: 

 (a) Air Flow 115 lpm. (4 cfm.) 

 Inhalation Resistance: 

 (b) Air Flow 85 lpm. (3 cfm.) 

 Exhalation Resistance: 

Comments: 

Test Engineer: 

Pass Fail 

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 9 of 10 

Appendix C 

Figures: 

1. Set up for Measuring Breathing Resistance. 

 

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Procedure No. RCT-APR-STP-0065 Revision: 1.1 Date: 12 September 2005 Page 10 of 10 

Revision History 

Revision Date Reason for Revision 

1.0 13 March 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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