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-0133 Revision: 1.1 Date: 21 September 2005

DETERMINATION OF EXHALATION BREATHING RESISTANCE - OPEN-CIRCUIT, PRESSUREDEMAND, SELF-CONTAINED BREATHING APPARATUS 

USING TWO SECOND STAGE REGULATORS 

STANDARD TESTING PROCEDURE (STP) 

1. PURPOSE

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

exhalation breathing resistance requirements on Open-Circuit, Pressure-Demand, Self-Contained 

Breathing Apparatus (SCBA) using Two Second Stage Regulators submitted for Approval, 

Extension of Approval, or examined during Approval 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 84.91(a)(c)(d) Volume 60, Number 110, June 8, 1995. 

2. GENERAL

This STP describes the Determination of Exhalation Breathing Resistance - Open-Circuit, 

Pressure-Demand, Self-Contained Breathing Apparatus Using Two Second Stage Regulators 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/MATERIAL

3.1. The list of necessary test equipment and materials follows: 

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

Indiana or equivalent.

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 
Procedure No. RCT-ASR-STP-0133 Revision: 1.1 Date: 21 September 2005 Page 2 of 8 

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

air flows - Model SR-085 or equivalent). 

3.1.3. Positive-pressure source calibrated at a flow of 85 1pm located on the silica dust 

chamber. (See Figure 1.) 

3.1.4. Ground Glass Joint 

3.1.5. Pinch Clamp 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 
Procedure No. RCT-ASR-STP-0133 Revision: 1.1 Date: 21 September 2005 Page 3 of 8 

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 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 

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

5.1. Assemble unit as per manufacturer’s instructions - except only hook up primary 

regulator. 

5.2. Mount facepiece on an anthropometric head fitted with a breathing tube, pressure tap, and 

ground glass joint connector. 

5.3. Turn on unit cylinder. 

5.4. To measure static pressure attach anthropometric head to slant manometer with pressure 

tap and block off ground glass connector. Allow at least one minute and read directly of 

manometer. 

5.5. To measure exhalation resistance, block off pressure tap and connect anthropometric 

head to positive blower adjusted to 85 liters per minute and read directly off manometer 

which is connected to positive blower. (See Figure 1.) 

5.6. Hookup secondary regulator, unhook primary regulator and repeat 5.2 through 5.5. 

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

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 
Procedure No. RCT-ASR-STP-0133 Revision: 1.1 Date: 21 September 2005 Page 4 of 8 

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), Subpart H, Section 84.91(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 

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

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

84.91 Breathing resistance test; exhalation. 

(a) Resistance to exhalation airflow will be measured in the facepiece or mouthpiece of 

open-circuit apparatus with air flowing at a continuous rate of 85 liters per minute. 

(c) The exhalation resistance of pressure-demand apparatus shall not exceed the static 

pressure in the facepiece by more than 51 mm. (2 inches) water-column height. 

(d) The static pressure (at zero flow) in the facepiece shall not exceed 38 mm. (1.5 

inches) water-column height. 

6.3. Modified Requirement 

In section 84.91, 42 CFR, Part 84 Breathing resistance test; exhalation resistance, a 

maximum static pressure of 1.5 inches of water-column height and an additional 

maximum pressure of 2 inches exhalation resistance is permitted for pressure-demand 

units. If the total exhalation resistance does not exceed 3.0 inches of water, then the 

static pressure may be increased by 0.5 inch or to a maximum of 2.0 inches of watercolumn height. 

Note: This modified requirement applies only to the primary regulator while the backup or 

secondary regulator must meet the static pressure requirement per 84.91(d), Part 84. In 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 
Procedure No. RCT-ASR-STP-0133 Revision: 1.1 Date: 21 September 2005 Page 5 of 8 

modifying this static pressure requirement by allowing an additional 0.5 inches of static 

pressure (increase of approximately 30%) the exhalation resistance level requirement was 

lowered by 1.0 inches of pressure (decrease of approximately 100%) thereby, reducing 

the scheduled maximum total respiratory workload by 15%. 

7. RECORDS/TEST SHEETS

7.1. All test data will be recorded on the BREATHING RESISTANCE - EXHALATION, 

OPEN-CIRCUIT, PRESSURE-DEMAND, SELF-CONTAINED BREATHING 

APPARATUS WITH TWO SECOND STAGE REGULATORS 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. 

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. 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 
Procedure No. RCT-ASR-STP-0133 Revision: 1.1 Date: 21 September 2005 Page 6 of 8 

BREATHING RESISTANCE - EXHALATION, OPEN-CIRCUIT, PRESSURE-DEMAND, 

SELF-CONTAINED BREATHING APPARATUS 

WITH TWO SECOND STAGE REGULATORS 

Project No.: Date: __________ 

Company : __________________________________________________ 

Respirator Type: ______________________________________________ 

Reference: 42 CFR, Part 84, Subpart H, Section 84.91(a)(c)(d). 

Requirements: 84.91(a) Resistance to exhalation airflow will be measured in the facepiece or 

mouthpiece of open-circuit apparatus with air flowing at a continuous rate of 85 liters per 

minute. 

84.91(c) The exhalation resistance of pressure-demand apparatus shall not exceed the 

static pressure in the facepiece by more than 51 mm. (2 inches) water-column height. 

84.91(d) The static pressure (at zero flow) in the facepiece shall not exceed 38 mm. (1.5 

inches) water-column height. 

Modified Requirement: 

In section 84.91, 42 CFR, Part 84 Breathing resistance test; exhalation resistance, a maximum 

static pressure of 1.5 inches of water-column height and an additional maximum pressure of 2 

inches exhalation resistance is permitted for pressure-demand units. If the total exhalation 

resistance does not exceed 3.0 inches of water, then the static pressure may be increased by 0.5 

inch or to a maximum of 2.0 inches of water-column height. 

Note: This modified requirement applies only to the primary regulator while the backup or 

secondary regulator must meet the static pressure requirement per 84.91(d). 

Results: 

 Primary Secondary Primary Secondary 

 Unit 1 "H2O Unit 1 "H2O Unit 2 "H2O Unit 2 "H2O

Exhalation: __________ 

Static: __________ 

Comments: 

_____________________________________________________________________________________

_____________________________________________________________________________________ 

Test Engineer: Pass Fail________ 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 
Procedure No. RCT-ASR-STP-0133 Revision: 1.1 Date: 21 September 2005 Page 7 of 8 

Figure 1. Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 
Procedure No. RCT-ASR-STP-0133 Revision: 1.1 Date: 21 September 2005 Page 8 of 8 

Revision History 

Revision Date Reason for Revision 

1.0 13 November 

2000 

Historic document 

1.1 21 September 

2005 

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

No changes to method 

 

 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy 

Uncontrolled Copy 

 Uncontrolled Copy