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. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005

DETERMINATION OF CBRN ACID GASES (SULFUR DIOXIDE) 

SERVICE-LIFE TEST, AIR-PURIFYING RESPIRATORS 

STANDARD TEST PROCEDURE (STP) 

1. PURPOSE

This test establishes the standard procedure for ensuring that the level of protection 

provided by the CBRN Acid Gases (Sulfur Dioxide) Service Life Test, Air-Purifying 

Respirators Standard test procedure submitted for Approval, Extension of Approval, or 

examined during Certified Product Audits meet the certification requirements 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) Full- Facepiece Air- Purifying Respirator (APR) Dated March 7, 2003.. 

2. GENERAL

This STP describes the Determination of CBRN Acid Gases (Sulfur Dioxide) Service Life 

Test, Air-Purifying Respirators Standard Test Procedure 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 AND MATERIAL

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

3.1.1 Flow-Temperature-Humidity Control System or equivalent. Miller-Nelson 

(MN) control system, Model HCS-201. 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 

three sensors and controlling mechanisms are incorporated electronically. 

The capacity of the unit is airflow: 20 to 200 liters / minute +/- 2%), 

relative humidity: 20 to 90 +/- 3 % and temperature ambient to 35 o

C +/- 

1o

C.

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Procedure No. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005 Page 2 of 8 

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% 

3.1.3 Interscan Corporation Model RM-24-0 sulfur dioxide detector or 

equivalent. This detector is an electrochemical voltammetric sensor. 

Detector range: 0 - 1999 ppm, resolution: 1 ppm. 

3.1.4 Interscan Corporation Model RM-24-2 sulfur dioxide detector or 

equivalent. This detector is an electrochemical voltammetric sensor. 

Detector range: 0 - 19.99 ppm, resolution: 0.01 ppm. 

3.1.5 Mass Flow Controller, Brooks Instruments, variable flow rate depending 

on use. 

3.1.6 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. 

3.1.7 Dry Gas Meter. Must have NIST traceable calibration certificate. 

3.1.8 Certified cylinders of 5 and 1500 ppm of sulfur dioxide in nitrogen. 

3.1.9 Sulfur dioxide cylinder, 99 percent purity. 

3.2 Test fixture for mounting canisters. 

3.3 The test chamber consisting of a 12" x 111⁄2" x 7" air tight metal box with door 

opening lined with gasket material. Two 1⁄2" bulkhead Swaglok® fittings located 

on the backside of 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 Resistance tester consisting of a vacuum source capable of delivering 85 Lpm, a 

6-inch water column slant manometer or electronic manometer and connections 

appropriate for items being tested. See description in RCT-APR-003 and RCTAPR-007. 

4. TESTING REQUIREMENTS AND CONDITIONS

4.1 This test procedure is only valid if the respirator system has first completed 

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Procedure No. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005 Page 3 of 8 

NIOSH Standard Test Procedure entitled Determination Of Durability Test For 

Environmental And Transportation Conditions And Rough Handling Drop Test 

On Chemical Biological Radiological Nuclear (CBRN) Air-Purifying Respirators 

(APR) And Canisters Standard Test Procedure (STP). 

4.2 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). 

4.3 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 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 follow on audits are requirements of the program. 

Additional details of the Program and its requirements can be obtained directly 

from the institute. 

4.5 Compressed gas cylinders must meet all applicable Department of Transportation 

requirements for cylinder approval as well as retesting / requalification. 

4.6 Normal laboratory safety practices must be observed. This includes safety 

precautions described in the current NIOSH Pittsburgh Health and Safety 

Program. 

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

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

equipment. 

4.6.3 When handling any broken glass laboratory equipment, lab technicians 

and personnel must wear special gloves, which protect against lacerations 

or punctures. 

4.7 Please refer to Material Safety Data Sheets and the NIOSH Health and 

Safety Manual for the proper protection and care in handling, storing, and 

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Procedure No. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005 Page 4 of 8 

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, calibrate both sulfur dioxide 

analyzers using the certified gas cylinder containing the 5 or 1500 ppm. 

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. 

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 percent purity. 

5.5 Establish the correct humidity and temperature as per the test standard in section 

6.3. 

5.6 Set the airflow to the required airflow for the test. Verify the airflow from the test 

fixture using the appropriate dry test meter. 

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

5.8 Take initial inhalation and exhalation resistances of the canister mounted on the 

facepiece and canister alone as described in RCT-APR-003 and RCT-APR-007. 

Record the values on Test Data Sheet. 

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Procedure No. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005 Page 5 of 8 

5.9 Make sure that the diverter valve in the system is diverting challenge airflow to 

the discharge and not into the testing chamber. 

5.10 Mount canister 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 1500 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. Monitor effluent concentration. Monitor upstream and downstream 

temperatures throughout testing, record beginning and final temperatures on the 

test data sheet. 

5.18 Run test until breakthrough of 5 ppm is observed or minimum service life is 

surpassed. Record this data on the test data sheet. 

5.19 Direct challenge concentration airflow out of the test chamber. 

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

5.6 Take final inhalation and exhalation resistances of the canister mounted on the 

facepiece and canister alone as described in RCT-APR-003 and RCT-APR-007. 

Record the values on Test Data Sheet. 

5.21 Allow clean air to purge through test chamber for 5 minutes 

5.22 Repeat steps 5.5 through 5.21 for each test described in section 6.3 

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

humidity to zero and allow air to pass through 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. 

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Procedure No. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005 Page 6 of 8 

 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 canisters 

6.3.1. Resistance to airflow of both canister and system will be taken before and 

after each test.. 

6.3.2. Three canisters will be tested at 64 Lpm, continuous air flow, 25 % ± 5 % 

relative humidity (RH), 25 oC ± 5 o

C, and 1500 ppm sulfur dioxide. 

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

manufacturer request. 

6.3.3 Three canisters will be tested at 64 Lpm, continuous air flow, 80 % ± 5 % 

relative humidity (RH), 25 o

C ± 5 oC, and 1500 ppm sulfur dioxide.

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

manufacturer request. 

6.3.4 Three canisters will be tested at 100 Lpm, continuous air flow, 50 % ± 5 

% relative humidity (RH), 25 o

C + 5 oC, and 1500 ppm sulfur dioxide. 

Minimum service life must be 5 minutes. 

6.3.5 End of service life concentration is 5 ppm sulfur dioxide. 

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Procedure No. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005 Page 7 of 8 

7. RECORDS AND 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 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-SOP-0005-00. 

8. ATTACHMENTS

 8.1 Bench Top Set-Up. 

8.2 Data Sheet. 

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Procedure No. CET-APRS-STP-CBRN-0306 Revision: 1.1 Date: 13 December 2005 Page 8 of 8 

Revision History 

Revision Date Reason for Revision 

00 20 September 2004 Historic document 

1.1 13 December 2005 Update header and format 

No changes to method 

 

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