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-0062 Revision: 1.1 Date: 6 September 2005

DETERMINATION OF NITROGEN DIOXIDE SERVICE LIFE TEST, 

AIR-PURIFYING RESPIRATORS 

STANDARD TESTING PROCEDURE (STP) 

1. PURPOSE

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

nitrogen dioxide service life requirements on chemical cartridge, air-purifying respirators 

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), and Subpart L, Section 84.190; Volume 60, Number 110, June 8, 1995. 

2. GENERAL

This STP describes the Determination of Nitrogen Dioxide Service Life Test, Air-Purifying 

Respirators 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. 

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

or equivalent.

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Procedure No. RCT-APR-STP-0062 Revision: 1.1 Date: 6 September 2005 Page 2 of 17 

 3.1.2. 

Interscan Corporation Model 1152 Nitrogen Dioxide Analyzer or equivalent. 

3.1.3. Nitrogen dioxide (NO2) cylinder, 99% purity with 61A-660 regulator. 

 3.1.4. 

Nitrogen dioxide certified gas cylinder, 1 ppm NO2, balance gas helium with 

3510-660 regulator. 

 3.1.5. 

Brooks Rotameters, R 215-D for cartridges or mass flow controller, 0-50 ml/min. 

 3.1.6. 

Digi Sense Scanning Thermocouple Thermometer Model 92800-10. 

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 3.1.7. 

Radiometer America Multi-Titration System, Model DTS 800, or equivalent. 

 

3.1.8. 

"The Gilbrator", Primary Standard Airflow Calibrator, or equivalent. 

 

3.1.9. 

Gilian Gil-Air-3 Sampling Pump, or equivalent. 

 

3.1.10. Water bath, cylinder wrap, or room heater, regulated to provide cylinder with 

constant 80-85o

F. 

3.1.11. 

Fisher Scientific Gas washing bottle or bubbler, catalog #03-036, or equivalent. 

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 3.1.12. 

Erlenmeyer flasks, 250 to 500 milliliters (mL). 

 3.1.13. 

Pipets, 5 mL. 

 3.1.14. Potassium Iodide (KI) (granular). 

 3.1.15. Potassium Iodate (KIO3) (granular). 

 3.1.16. Starch, Soluble Potato, Powder. 

 3.1.17. Boric Acid (granular). 

 3.1.18. Sodium Thiosulfate (Na2S2O3) (granular). 

 3.1.19. 

Electronic Balance with an accuracy of 0.001 grams (g). 

3.1.20. 

Houston Instruments, Model 451BE, strip chart recorder or equivalent. 

 3.1.21. Test fixture for holding cartridges. The test fixture is specific to each 

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Procedure No. RCT-APR-STP-0062 Revision: 1.1 Date: 6 September 2005 Page 5 of 17 

manufacturer depending on how the cartridge is mounted to the facepiece. In 

most cases the cartridge cups of the respirator are affixed by hot melt glue to a 

PVC pipe tee of appropriate size. The T end has a 29/42 ground glass joint glued 

in place. 

3.1.22. 

Test chamber consisting of a 12" x 111⁄2" x 7" air tight box, made of 

1⁄2" plexiglass with two hinge type locks on the door opening lined with gasket 

material. A 1⁄2" hole is located on the back side of the test chamber for the 

introduction of the test concentration, and a 11⁄2" hole on the top for the exit of 

the test fixture and to detect the breakthrough concentration. This fixture is not 

commercially available. 

3.1.23. 

Resistance tester consisting of a vacuum source capable of delivering 85 liters 

per minute (lpm), a 6-inch slant manometer, a 29/42 female ground glass joint. 

The resistance testers currently being used are located on the silica dust and lead 

fume chambers. 

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. 

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

described in the current ALOSH Facility Laboratory Safety Manual. 

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Procedure No. RCT-APR-STP-0062 Revision: 1.1 Date: 6 September 2005 Page 6 of 17 

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

4.2.2. Work benches must be maintained free of clutter and non-essential test 

equipment. 

4.2.3. When handling any glass laboratory equipment, lab technicians and personnel 

must wear special gloves which protect against lacerations or punctures. 

 4.3. NITROGEN DIOXIDE BENCH TEST FOR CARTRIDGES 

 4.3.1. Resistance to air flow will be taken before and after each test 

 (see 84.203). 

4.3.2. Three "as received" cartridges (or pairs of cartridges) will be tested at 64 lpm, 

continuous air flow, 50 " 5% relative humidity (RH), approximately 25 degrees 

Celsius (°C), and 500 ppm of NO2. 

 4.3.3. Two cartridges or pairs of cartridges will be equilibrated at room temperature by 

passing 25% RH air through them at 25 lpm for 6 hours and then testing them at 

25% RH, approximately 25°C, and 64 lpm continuous flow rate containing 500 

ppm NO2. 

 4.3.4. Two cartridges or pairs of cartridges will be equilibrated at room temperature by 

passing 85% RH air through them at 25 lpm for 6 hours and then testing them at 

85% RH, approximately 25°C, and 64 lpm continuous flow rate containing 500 

ppm NO2. 

 4.4. Please refer to Material Safety Data Sheet 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, calibration, and maintenance of 

equipment used in this procedure prior to beginning any 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 warmup period, calibrate the NO2 analyzer using the 

certified gas cylinder containing the 1 ppm standard as follows: 

5.2.1. With a tee in line on the gas cylinder, insert the intake tubing into the tee. 

5.2.2. Turn on the cylinder. 

5.2.3. Wait till reading stabilizes, and adjust span control to read 1 ppm. 

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 5.3. Prepare solutions: 

 5.3.1. 5% Potassium Iodide/1% Potassium Iodate: Dissolve 50 g KI and 10g KIO3 in 1 

liter distilled water. 

 5.3.2. 0.0025 Normal (N) Sodium Thiosulfate Solution: Dissolve 0.6205 g sodium 

thiosulfate in 1 liter of distilled water. Commercially bought certified sodium 

thiosulfate solutions can be used. 

 5.3.3. Starch Indicator: Weigh 1 g boric acid and add to 100 mL of distilled water, 

bring to a boil. 

5.3.3.1. Weigh 1-2 g potato starch, add cold water to make a paste. 

 5.3.3.2. Add to boiling water and continue to boil for 1 minute. 

 5.3.3.3. Discard when starch solution becomes cloudy. 

 5.4. Connect the Gil-Air-3 Sampling Pump to the Gillibrator and calibrate to draw 1 lpm. 

This will be used to draw and collect the test concentration sample onto the KI/KIO3

solution. 

 5.5. Set up test equipment as shown in Figure 1. 

 5.6. Heat cylinder to 80-85o

F to force nitrogen dioxide gas from cylinder. 

 5.7. Turn on: 

 5.7.1. Miller Nelson Unit. 

 5.7.2. Air and water supplies. 

 

5.7.3. NO2 cylinder. 

 5.7.4. NO2 analyzer. 

 5.8. Establish test concentration for approximately 500 ppm NO2. 

 5.9. Measure 100 mL of the 1%KIO3/5% KI solution into the gas bubbler. Attach Gil-Air 3 

sampling pump to intake side of the gas bubbler. Connect outlet side of bubbler to 

Gillibrator. Check 1 lpm flow of the pump pulling through the 1%KIO3/5% KI solution. 

 5.10. Adjust the rotameter or flow controller to deliver approximately 32 cc/min. NO2 into the 

airstream to obtain 500 ppm NO2. 

 5.11. Connect sample side of gas bubbler into the Gil-Air-3 Sampling Pump and intake into the 

test gas concentration. 

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Procedure No. RCT-APR-STP-0062 Revision: 1.1 Date: 6 September 2005 Page 8 of 17 

 5.12. Turn pump on and sample at 1 lpm for 10 minutes. The KI/KIO3 solution should change 

to dark yellow in the presence of nitrogen dioxide. 

 5.13. Remove gas bubbler, and transfer the solution into an Erlenmeyer flask. 

 5.13.1. Rinse the gas bubbler with distilled water and transfer the washings into the 

flask. 

 5.14. Titrate the solution with 0.0025N sodium thiosulfate until it is pale yellow. 

 5.15. Add 5 mL of starch indicator. Solution will turn dark blue. 

 5.16. Continue titration until the blue color just disappears. 

5.17. Calculate the concentration of NO2 in air using the following formula: 

 9.168 x mL of .0025N Na2S2O3 = ppm NO2

 5.18. Once the NO2 concentration has been established testing may begin. 

 5.19. Weigh the cartridge and record the weight. 

 5.20. Take inhalation and exhalation resistances of the cartridges mounted on the facepiece at 

85 lpm. See Section 84.203 Title 42, Code of Federal Regulations, Part 84 for breathing 

resistance requirements. 

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

 5.22. Direct challenge concentration airflow into test chamber. Start timer. Mount small piece 

of tygon tubing onto outlet of test fixture. Insert intake tubing of detector into side wall 

of tygon tubing to allow the detector to sample at the flow rate of the detector without 

interference from airflow back pressure. Monitor and record upstream and downstream 

temperatures throughout testing. Record breakthrough values and times. 

5.23. Run test until breakthrough of 1.0 ppm is observed or minimum service life is surpassed. 

 5.24. Dismount cartridge or canister, weigh and record final weight, and take final inhalation 

and exhalation resistances. 

 5.25. Turn off nitrogen dioxide cylinder. 

 5.26. Allow clean air to purge system for 15 minutes. Disconnect NO2 tubing from test system 

to prevent humidity sensor contamination. 

 5.27. Turn off air and water supply. 

 5.28. Turn off Miller Nelson System. 

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 5.29. Turn off nitrogen dioxide detector. 

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 L, Section 84.190; 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. 

 84.190 Chemical cartridge respirators: description. 

(a) Chemical cartridge respirators including all completely assembled respirators which 

are designed for use as respiratory protection during entry into or escape from 

atmospheres not immediately dangerous to life and health, are described according to the 

specific gases or vapors against which they are designed to provide respiratory 

protection, as follows: 

Type of chemical cartridge respirator1 Maximum use concentration, parts per 

million 

Ammonia 300 

Chlorine 10 

Hydrogen chloride 50 

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Procedure No. RCT-APR-STP-0062 Revision: 1.1 Date: 6 September 2005 Page 10 of 17 

Methyl amine 100 

Organic vapor 21,000 

Sulfur dioxide 50 

Vinyl chloride 10 

1

Not for use against gases or vapors with poor warning properties (except where MSHA or Occupational 

Safety and Health Administration standards may permit such use for a specific gas or vapor) or those 

which generate high heats of reaction with sorbent material in the cartridge. 

2

Maximum use concentrations are lower for organic vapors which produce atmospheres immediately 

hazardous to life or health at concentrations equal to or lower than this concentration. 

(b) Chemical cartridge respirators for respiratory protection against gases or vapors, 

which are not specifically listed with their maximum use concentration, may be approved 

if the applicant submits a request for such approval, in writing, to the Institute. The 

Institute shall consider each such application and accept or reject the application after a 

review of the effects on the wearer's health and safety and in the light of any field 

experience in use of chemical cartridge respirators as protection against such hazards. 

 6.3 The criterion for passing this test is that the penetration of NO2 shall not exceed 1.0 ppm 

for a minimum service life of 30 minutes (Standard SO2 test time) for negative pressure 

cartridges. If the penetration does not exceed 1.0 ppm during the service life of 30 

minutes for negative pressure cartridges, the units pass the test. If the penetration does 

exceed 1.0 ppm for a minimum service life of 30 minutes for negative pressure 

cartridges, the units fail the test. The units will be run until the penetration of NO2 is 

equal to 1.0 ppm. 

7. RECORDS/TEST SHEETS

 7.1. All test data will be recorded on the NITROGEN 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 

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Procedure No. RCT-APR-STP-0062 Revision: 1.1 Date: 6 September 2005 Page 11 of 17 

for Scheduling, and Processing Post-Certification Product Audits, 

RB-SOP-0005-00. 

8. ATTACHMENTS

 8.1. List of Test Equipment Manufacturers. 

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Procedure No. RCT-APR-STP-0062 Revision: 1.1 Date: 6 September 2005 Page 12 of 17 

Attachment 8.1.

8.1.1. Miller Nelson Research 

 8 Harris Court 

 Monterey, CA 93940 

 408-647-1551 

8.1.2. Interscan Corporation 

 21700 Nordhoff St. 

 Chatsworth, CA 91311 

8.1.3. Matheson Gas Products 

 1650 Enterprise Parkway 

 PO Box 358 

 Twinsburg, OH 44087 

8.1.4. Brooks Instrument Div. 

 Emerson Electric Co. 

 Hatfield, PA 07630 

8.1.5. Radiometer America 

 811 Sharon Drive 

 Westlake, OH 44145 

8.1.6. Gilian Instrument Corp. 

 35 Fairfield Place 

 W. Caldwell, NJ 07006 

8.1.7. Fisher Scientific 

 585 Alpha Drive 

 Pittsburgh, PA 15338 

8.1.8. Cole Parmer Instrument Co. 

 7425 North Oak Park Avenue 

 Niles, IL 60714 

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Revision History 

Revision Date Reason for Revision 

1.0 5 June 2000 Historic document 

1.1 6 September 

2005 

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

No changes to method 

 

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