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National Institute for Occupational Safety and Health

National Personal Protective Technology Laboratory

P.O. Box 18070

Pittsburgh, PA 15236

Procedure No. TEB-CBRN-ASR-STP-0220 Revision: 0.1 Date: 30 January 2014

DETERMINATION OF POSITIVE PRESSURE - OPEN-CIRCUIT, 

PRESSURE-DEMAND, SELF-CONTAINED BREATHING APPARATUS (SCBA) DURING 

EMERGENCY BREATHING SAFETY SYSTEM (EBSS) FULL FLOW OPERATION 

STANDARD TESTING PROCEDURE (STP) 

1. PURPOSE 

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

positive pressure requirements on Open-Circuit, Self-Contained Breathing Apparatus (SCBA) 

equipped with the Emergency Breathing Safety System(EBSS) option 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 84.70(a)(2)(ii); Volume 60, Number 110, June 8, 1995. 

2. GENERAL 

This STP describes the Determination of Positive-Pressure Open-Circuit, Pressure-Demand, SelfContained Breathing Apparatus during full flow activation of the Emergency Breathing Safety 

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

air flows - Model SR-085 or equivalent. 

3.1.3. Temperature compensated pressure transducer (Validyne Engineering Model No. 

DP45) or equivalent. 

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

Company) or equivalent. 

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

City, Indiana or equivalent. 
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3.1.6. Two channel thermal tip recording system (Gould Model No. RS3200) with 

carrier amplifier (Model No. 13-4615-35) 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 

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

5.1. Turn on recorder and allow at least 30-minutes warm up. 

PRE-TEST BALANCING OF TRANSDUCER AND RECORDER 

5.1.1. Connect the transducer to be used during testing in parallel with a manometer. 
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Attach the manometer and transducer to a pressure regulated air. A pinch clamp, 

used for slight pressure changes, is placed inline with two equal lengths of tubing 

for the manometer and transducer connections. 

5.1.2. Connect the transducer cable to the carrier amplifier in the chart. Calibrate the 

recorder and carrier amplifier per instruction manual. Press the 5 mm/sec chart 

speed button. With no load applied to the transducer/manometer system, adjust 

the “POSITION” potentiometer on the chart recorder until the pen is at the midscale position. Press the STOP button on the chart recorder. 

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

Press the 5 mm/sec chart speed button. Adjust the “CAL” potentiometer on the 

carrier amplifier until the pen on the chart recorder is at the next bold line left of 

mid-scale position. This represents 0.5 inches of water. Press the STOP button 

on the chart recorder. 

5.1.4. Reduce the pressure to 0.0 inches of water to the transducer/manometer system. 

Press the 5 mm/sec chart speed button and check that the chart recorder pen is at 

the zero mid-scale position. Make any necessary adjustments. Press the STOP 

button on the chart recorder. 

5.1.5. Repeat steps 5.1.3 and 5.1.4 with a pressures of 1.0, 1.5, and 2.0 inches of water 

until no adjustments are necessary at the “CAL” potentiometer on the carrier 

amplifier. 

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

system. 

5.2. Assemble the apparatus as shown in Figure 1. Mount the pressure transducer where 

shock and vibration are minimal. 

5.3. Fill SCBA cylinder with air to pressure as noted in the instruction manual. Make sure the 

pressure is within the DOT certified pressure range. A “+” indicates that the DOT 

pressure may be exceeded by 10%. 

5.4. Assemble respirator. Mount the facepiece on the 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 attaching the pressure probe to a digital or inclined 

manometer, and use a small vacuum pump attached to the 3⁄4” copper tube from the back 

of the headform, with a shut-off valve in line, to create a negative pressure in the 

facepiece. Close off the shut-off valve when a pressure of minus 2-3 inches of water is 

achieved in the facepiece, and start timing the loss of vacuum from -1 inch to -0.8 inches 

of water. If the vacuum decay rate from 1inch to - 0.8 inches of water is more than 5 

seconds, the seal is acceptable. 

5.5. Connect regulator or breathing tube to facepiece. Do not connect head to breathing 

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

cam is operating at 24 rpm. (This will give a 40 lpm volume). 
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5.6. Zero the recorder base-line to mid point of chart paper. (While this is being done the 

transducer should be connected to the recorder but the transducer should not have any 

load on it). 

5.7. Connect the anthropocentric head with the facepiece to the breathing machine. Connect 

transducer to resistance port with a short length of tubing. Open cylinder valve full and 

open main line valve full. Make sure the by-pass valve is closed and the EBSS line is 

secure to prevent hose whip during test. 

5.8. Record all attenuation and speed settings directly on chart paper. Turn on breathing 

machine, timer and recorder simultaneously, and set the chart speed to 20 mm/sec for the 

duration of the test. Record three full breathing cycles prior to activation of the EBSS 

(Full flow will be achieved by connecting a manufacturer supplied male or female quick 

connect to the EBSS connection venting to atmosphere). 

5.9. Testing is complete when the first inhalation trace goes below zero (stop the timer). 

Terminate the test by stopping the breathing machine, securing the cylinder valve on the 

SCBA and then bleed down the high-pressure air trapped in the breathing hose by 

opening the by-pass valve and then shut the by-pass off. 

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

5.11. Data Analysis 

5.11.1. The recorder produces a trace showing the inhalation (negative) and exhalation 

(positive) breathing resistance. For this test the total duration the inhalation peak 

values remain positive is the component for analysis. With a chart speed of 20 

mm/sec., the inhalation phase should measure approximately 50 mm. 

5.11.2. For a pressure-demand unit the peak valves of the inhalation tracings shall 

remain positive with respect to the base-line (zero) established at the time the 

recorder is calibrated. (See Figure 2.) At a speed of 20 mm/sec, 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. 

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 84.70(a)(2)(ii); Volume 60, Number 110, June 8, 

1995. 

6.2. This test establishes the standard procedure for ensuring that: 
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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. 

84.70 Self-contained breathing apparatus; description. 

(a) Self-contained breathing apparatus, including all completely assembled, portable, selfcontained devices designed for use as respiratory protection during entry into and escape 

from or escape only from hazardous atmospheres, are described as follows: 

(2) Open-circuit apparatus. An apparatus of the following types from which exhalation is 

vented to the atmosphere and not rebreathed: 

(ii) Pressure-demand-type apparatus. An apparatus in which the pressure inside the 

facepiece in relation to the immediate environment is positive during both inhalation and 

exhalation. 

6.3. Pressure-demand type apparatus. 

This test establishes the standard procedure for ensuring that an apparatus with its EBSS 

operating in a full flow condition maintains positive pressure inside the facepiece in 

relation to the immediate environment during both inhalation and exhalation and is done 

at full cylinder pressure to the point at which the inhalation portion drops below the 

baseline (zero) during the test. 

7. RECORDS\TEST SHEETS 

7.1. All test data will be recorded on the POSITIVE PRESSURE TEST, OPEN-CIRCUIT, 

SELF-CONTAINED BREATHING APPARATUS test data sheet. 

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 
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Procedure No. TEB-CBRN-ASR-STP-0220 Revision: 0.1 Date: 30 January 2014 Page 7 of 14

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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Procedure No. TEB-CBRN-ASR-STP-0220 Revision: 0.1 Date: 30 January 2014 Page 8 of 14

POSITIVE PRESSURE TEST, OPEN-CIRCUIT, SELF-CONTAINED BREATHING 

APPARATUS DURING EMERGENCY BREATHING SAFETY SYSTEM FULL FLOW 

OPERATION 

Project No. : Date: __________ 

Company : ________________________________________ 

Respirator Type: ________________________________________ 

Reference: 42 CFR Part 84, Subpart H, Section 84.70(a)(2)(ii), 

Requirements: 84.70(a)(2)(ii) Pressure-Demand Type Breathing Apparatus - An apparatus in which the 

pressure inside the face piece in relation to the immediate environment is positive during 

both inhalation and exhalation. 

Procedure: A breathing machine with a 622 kg. -m./min. Cam operating at 24 rpm with a 40 lpm 

volume (115 lpm peak flow) is connected to an anthropometric head for cycling. A 

pressure tap in the head is connected to a transducer which in turn is connected to a strip 

chart recorder for determining the pressure in the face piece. After three full breathing 

cycles the EBSS line will be engaged and full line air flow will be exhausted until the 

cylinder is empty. 

Results: 

Facepiece pressure 

 

Unit #1 > or = ambient ; < ambient ; 

Cylinder Pressure Rating:________ Time Elapsed to Empty Cylinder:___________ 

Unit #2 > or = ambient ; < ambient ; 

Cylinder Pressure Rating:________ Time Elapsed to Empty Cylinder:___________ 

Comments: 

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________ 

Test Engineer: PASS FAIL________ 
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Figure 1 

Test Set-up for Measuring Inhalation Breathing Resistance 
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Figure 2 
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Revision History 

Revision Date Reason for Revision

0.0 6 January 2014 Establishment of procedure

0.1 30January 2014 Incorporate new mask leakage test, new system schematic, and new 

photos