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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-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009

DETERMINATION OF CBRN ACID GASES (SULFUR DIOXIDE) SERVICE 

LIFE TEST, LOOSE-FITTING POWERED AIR-PURIFYING RESPIRATORS 

(PAPR) STANDARD TEST PROCEDURE (STP) 

1. PURPOSE

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

Determination of CBRN Acid Gases (sulfur dioxide) Service Life Test, Loose-Fitting Powered 

Air-Purifying Respirators (PAPR) Standard Test Procedure 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); Volume 60, Number 110, June 8, 

1995 and the Statement of Standard for Chemical, Biological, Radiological, and Nuclear (CBRN) 

Powered Air-Purifying Respirators (PAPR).

 

2. GENERAL

This STP describes the Determination of CBRN Acid Gas (sulfur dioxide) Service Life Test, 

Loose-Fitting Powered Air-Purifying Respirators (PAPR) Service Life Test, Standard Test 

Procedure 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 AND MATERIAL

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

3.1.1. Miller Nelson Research Model 401 Flow-Temperature-Humidity Control System 

or equivalent. This system is an automated system to control the airflow, 

temperature, and humidity of an air supply for an operating system. Laboratory 

air and distilled water are supplied to the unit. The unit output is air of the 

variable volume/flow dependant on the size of unit (10% of max flow to max 

flow in liters per minute (Lpm)  2%), and relative humidity (10%–98%  3%) 

and temperature (20oC–30o 0

C  0.3%). 

3.1.2. EdgeTech Dew Prime II Hygrometer, Model 2000 or equivalent. A microprocessor based programmable chilled mirror dew point hygrometer. The 

hygrometer uses the dew point and ambient temperature to calculate the relative 

humidity. Ambient temperature range is: -50oC to 130oC  0.2oC; relative 

humidity is 1% to 95%  0.5%. 

Approvals: First Level Second Level Third Level Fourth Level 

 
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 2 of 10 

3.1.3. Labview software developed for NIOSH Service Life Test. 

3.1.4. Interscan Corporation Model RM-17-0 sulfur dioxide detector or equivalent. This 

detector is an electrochemical voltammetric sensor. Detector range: 0 - 1999 

ppm, resolution: 1 ppm. 

3.1.5. Interscan Corporation Model RM-17-2 sulfur dioxide detector or equivalent. 

This detector is an electrochemical voltammetric sensor. Detector range: 0 - 

19.99 ppm, resolution: 0.01 ppm. 

3.1.6. Mass Flow Controller, Brooks Instruments, variable flow rate depending on use. 

3.1.7. Read out and Control Electronics, Brooks Instruments, Model 0154. Power 

supply and controller for the Brooks Mass Flow Controller or equivalent. The 

flow controllers are an integrally mounted control valve module with which 

stable gas flows can be achieved. Various flow rates are used with an accuracy of 

 0.7 % of rate and  0.2 % full scale. 

3.1.8. Dry Test Meter. American Meter Co., model and size depending on air flow rate 

to be measured. Must have NIST traceable calibration certificate. 

3.1.9. Certified cylinders of approximately 5 ppm and 750 ppm sulfur dioxide in 

nitrogen. 

3.1.10. Sulfur dioxide cylinder, 99 % purity. 

3.2. Test fixture for mounting cartridges. 

3.3. The test chamber consisting of an air-tight box with door opening lined with gasket 

material. Two fittings located on the test chamber for the introduction of the test 

concentration and for the exit of the test fixture. This fixture is not commercially 

available. 

3.4. Airflow measurement equipment as described in standard test procedure RCT-APR0012. 

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. Any laboratory using this procedure to supply certification test data to NIOSH will be 

subject to the provisions of the NIOSH Supplier Qualification Program (SQP). This 

program is based on the tenets of ISO/IEC 17025, the NIOSH Manual of Analytical 

Methods and other NIOSH guidelines. An initial complete quality system audit and 
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 3 of 10 

follow on audits are requirements of the program. Additional details of the Program and 

its requirements can be obtained directly from the institute. 

4.3. Precision and accuracy (P&A) must be determined for each instrument in accordance 

with laboratory procedures and NIOSH/NPPTL guidance. Sound practice requires, under 

NIOSH Manual of Analytical Methods, demonstrating a tolerance range of expected data 

performance of a plus or minus 25% of a 95% confidence interval of the stated standard 

requirement. NIOSH/NPPTL P&A tolerance can be higher but not lower. 

4.4. Compressed gas cylinders must meet all applicable Department of Transportation 

requirements for cylinder approval as well as retesting / requalification. 

4.5. Normal laboratory safety practices must be observed. This includes safety precautions 

described in the current NIOSH Pittsburgh Health and Safety Program. 

4.5.1. Safety glasses, lab coats and hard-toe shoes must be worn at all times. 

4.5.2. Workbenches must be maintained free of clutter and non-essential test 

equipment. 

4.5.3. When handling any broken glass laboratory equipment, lab technicians and 

personnel must wear special gloves, which may protect against lacerations or 

punctures. 

4.6. Please refer to Material Safety Data Sheets and the NIOSH Health and Safety 

Manual for the proper protection and care in handling, storing, and disposing of the 

chemicals and gases used in this procedure.

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. Follow individual instruction manuals for set up and maintenance of equipment used in 

this procedure prior to beginning testing. Malfunctioning equipment must be repaired or 

replaced and properly set up and calibrated before starting all tests. 

5.2. After the manufacturer's specified warm-up period adjust instruments to read zero and 

make adjustment for Labview software to read 0 ppm. The challenge monitor is 

calibrated from the challenge concentration of approximately 750 ppm using the certified 

gas cylinder and the downstream monitor is calibrated for the breakthrough concentration 

of approximately 5 ppm using the certified gas cylinder. 

 

5.3. Set up test equipment as shown in Figure 1. The humidity reading controlled by the 

Miller Nelson system and monitored the Dew Point Hygrometer. The sample pickup for 

the hygrometer is place into the air stream via a tee after the Miller Nelson and before the 

introduction point of challenge agent. The thermocouple for the hygrometer is placed in 

the challenge gas stream immediately before the test chamber. 
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 4 of 10 

5.4. Verify the following equipment is on: 

5.4.1. Miller Nelson Unit. 

5.4.2. Air and water supplies. 

5.4.3. NIOSH Service Life Apparatus Controller software program. 

5.4.4. Sulfur dioxide cylinder, 99 % purity.

5.5. Establish the correct humidity and temperature as per the test standard in paragraph 6.3. 

5.6. Set the required airflow for the system. Individual cartridges will be tested by dividing 

170 Lpm by the number of air purifying elements on the system. See appendix 8.2. 

Verify the airflow from the test fixture using the appropriate dry test meter. 

5.7. Weigh and record initial weight of the test cartridge on Test Data Sheet. 

5.8. Take and record initial airflow measurements in accordance with RCT-APR-012. See 

section 84.1702 (b) Title 42, Code of Federal Regulations, Part 84 for minimum airflow 

requirements. 

5.9. Ensure that the diverter valve in the system is diverting the challenge concentration 

airflow to discharge and not into the testing chamber. 

5.10. Mount cartridge onto test fixture and place in testing chamber. 

5.11. Divert 0.5 Lpm airflow from air flow line to the sulfur dioxide challenge detector. 

5.12. Ensure that the nitrogen gas is ready for immediate flushing of regulator through the 

purge valve. 

5.13. Turn on sulfur dioxide cylinder. 

5.14. Establish the test concentration of 750 ppm  75 ppm sulfur dioxide. 

5.15. Once the sulfur dioxide concentration has been established, testing may begin. 

5.16. Direct challenge concentration airflow into test chamber. 

5.17. Start timer. Airflow out of the test chamber is directed into the breakthrough detector. 

Monitor and record the upstream and downstream temperatures of the airflow throughout 

test. 

5.18. Run test until breakthrough of 5 ppm is observed or selected service life time is 

surpassed. Record this data on the test data sheet. 
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 5 of 10 

5.19. Direct challenge concentration airflow out of the test chamber. 

5.20. Weigh and record final weight of the test cartridge on Test Data Sheet. 

5.21. Take and record final airflow measurements in accordance with RCT-APR-012. See 

section 84.1702 (b) Title 42, Code of Federal Regulations, Part 84 for minimum airflow 

requirements. 

5.22. Allow clean air to purge through system for 5 minutes. 

5.23. Repeat steps 5.5 through 5.22 for each test described in section 6.3. 

5.24. When all tests are completed turn off sulfur dioxide cylinder, set temperature and 

humidity to zero and allow air to pass through the system for 30 minutes. 

6. PASS OR 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); 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. 

6.3. Acid Gas (sulfur dioxide) test for CBRN cartridges 

6.3.1. Airflow measurements of system must be taken before and after each test. 

6.3.2. Three cartridges will be tested at the determined continuous air flow, 25 %  2.5 

% relative humidity (RH), 25 o

C  2.5 oC and 750 ppm sulfur dioxide. 

6.3.3. Three cartridges will be tested at the determined continuous air flow, 80 %  2.5 

% relative humidity (RH), 25 o

C  2.5 oC and 750 ppm sulfur dioxide. 
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 6 of 10 

6.3.4. Minimum service life will be 15, 30, 45, 60, 90 or 120 minutes as per 

manufacturer request. End of service life concentration is 5 ppm sulfur dioxide. 

7. RECORDS OR TEST SHEETS

7.1. All test data will be recorded on the SULFUR DIOXIDE SERVICE LIFE 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 TEB Team 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 TEB Team 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 Branch Chief, or 

the Branch Chief’s designee, following the standard operating procedures 

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

Audits, RB-SOP-0005-00. 

8. APPENDIXES

 8.1. Bench Top Set-Up 

8.2. Test Data Sheet 

8.3. Service life testing airflow calculations
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 7 of 10 

8.1. Bench Top Set-Up 
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 8 of 10 

8.2. Test Data Sheet
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 9 of 10 

8.3. Service-life testing airflow calculations 

Loose-fitting PAPR 

___________ Number of filtering elements on a loose-fitting PAPR System. 

170 Lpm airflow 

Airflow for service life test = 170 Lpm / number of filtering elements 

Test Flow 

4 Cartridges 3 Cartridges 2 Cartridges 1 Cartridge 

28.8 Lpm 38.3 Lpm 57.5 Lpm 170 Lpm 
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Procedure No. TEB-APR-STP-0516-CBRN Revision: 0.1 Date: 9 February 2009 Page 10 of 10 

Revision History 

Revision Date Reason for Revision 

0.0 21 November 2006 Original Issue 

0.1 9 February 2009 Name changed in alignment with current naming convention, 

paragraph 6.3.4. correctly numbered to reflect its inherent order, 

minor editorial revision, no change to procedure