National Institute for Occupational Safety and Health 

National Personal Protective Technology Laboratory 

P.O. Box 18070 

Pittsburgh, PA 15236 

Procedure No. TEB-APR-STP-0039C Revision: 2.1 Date: 3 February 2009

DETERMINATION OF FORMALDEHYDE SERVICE LIFE TEST, 

POWERED AIR-PURIFYING RESPIRATORS WITH CARTRIDGES 

 STANDARD TESTING PROCEDURE 

1. PURPOSE

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

air-purifying respirators (PAPR) with cartridges submitted for Approval, Extension of Approval, 

or examined during Certified Product Audits meet the formaldehyde service life requirements set 

forth in 42 CFR Part 84, Subpart G, Section 84.63(a)(c)(d), Subpart L, Section 84.190(b) and 

Subpart KK, Section 1157 (f). 

2. GENERAL

This Standard Testing Procedure (STP) describes the Determination of Formaldehyde Service 

Life Test, Air-Purifying Respirators with Cartridges 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 / REFERENCES

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

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

(250 lpm) or equivalent. Air flow control accuracy is ± 2% F.S. Temperature 

control accuracy is ± 1° C. Humidity control accuracy is ± 3% R.H. 

3.1.2. Edge Tech Heated Dew Point Hygrometer with platinum mirror, Model DPS1 or 

equivalent. Accuracy is ± 0.2° C, ±0.5% RH. 

 3.1.3. Interscan Corporation Model 1168 Formaldehyde Monitor 0-1999 ppb or 

equivalent. Accuracy ±2.0% of reading, ±1 least significant digit. 

3.1.4. Mass Flow Controllers, Brooks Instruments model series 5850S and 5853S with 

Read Out and Control Electronics, Brooks Instruments model 0154, variable flow 

rate depending on use. Accuracy is 0.7% set point & 0.2% FS. 

3.1.5. American Meter Co. Dry Test Meter Model DTM-325. 

Approvals: First Level Second Level Third Level Fourth Level 

 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 2 of 14 

3.1.6. Amersham Biosciences High Precision Pump, Model P-500 with reservoir. Flow 

rate range: l ml/hr to 400 ml/hr ± 1.5% of setting. 

3.1.7. Electronic balance with an accuracy of 0.01grams. 

3.1.8. Miller Nelson Research, Model SV-2000 Vaporizer system or equivalent. Used 

for vaporizing formaldehyde solution. 

3.1.9. Kin-Tek Laboratories Inc. Model 491M Precision Gas Standards Generator. 

3.1.10. Permeation tubes of formaldehyde. Used for the calibration of formaldehyde 

 detectors. 

3.1.11. "The Gilibrator", Primary Standard Airflow Calibrator or equivalent. 

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

3.1.13. Graduated impinger, 25ml. 

3.1.14. Erlenmeyer flasks, 100 and 250 ml, beakers, 200 and 600 ml, polyethylene 

bottles, 500 ml, and flasks with ground glass joints, 1000 and 2000 ml. 

3.1.15. Pipets, 5 and 10 ml. 

3.1.16. Electronic balance with accuracy of 0.01 gram (g). 

 3.1.17. Paraformaldehyde, purified grade ≥ 95%. 

 3.1.18. Sodium thiosulfate (granular) or 0.1N certified sodium thiosulfate solution. 

 3.1.19. Starch, soluble potato, powder. 

 3.1.20. Iodine, 0.1N certified solution. 

 3.1.21. Sodium bisulfite, granular. 

 3.1.22. Sodium carbonate, anhydrous powder. 

 3.1.23. Glacial acetic acid. 

 3.1.24. Hot plate with magnetic stirrer and stir bar. 

 

 3.1.25. Media bottles, Pyrex Plus, 1000 ml. 

3.2. Test fixture for mounting cartridges inside the test chamber. The test fixture used is 

specific to each manufacturer depending on how the cartridge is mounted to the 

facepiece. Some cartridges use a standard 40 mm male thread which mates with the test 

port in the chamber. In some cases the manufacturer is willing to provide a machined 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 3 of 14 

adapter for mounting cartridges with unique threads. Alternatively, the cartridge adapters 

of the respirator are affixed by hot melt glue to a PVC pipe tee of appropriate size which 

mates with the test port. All adapters are checked for leak-tightness with soap solution. 

3.3. The test chamber consisting of an approximately 12" x 12" x 7" air tight box, with 2 

clamp type locks on the door opening lined with gasket material, and appropriate inlet, 

outlet and sampling ports. This fixture is not commercially available. 

3.4. Refer to the following Work Instructions for further information on performing this test: 

 TEB-RCT-APR-WI-1007 – Laboratory Safety Procedures for Formaldehyde Tests 

 TEB-RCT-APR-WI-1107 – Calibration Procedures for Formaldehyde Tests 

TEB-RCT-APR-WI-1207 – Start–Up and Shut–Down Procedures for Formaldehyde 

 Tests 

TEB-RCT-APR-WI-1407 – Reporting Results for Formaldehyde Tests 

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 testing laboratory’s calibration procedure and schedule. 

All measuring equipment utilized for this testing must have been calibrated using a 

method traceable to the National Institute of Standards and Technology (NIST) when 

available. 

4.2. Any laboratory using this procedure to supply certification test data as a contractor 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.* 

*Note 4.2 does not apply to Pretest data from applicants as required under 42 CFR 

84.64. 

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. The precision and accuracy of this method was determined by validation testing of a 

single lot of commercially available multi-gas type cartridges. The results of these tests 

are shown in the table below. 

 

TEST TYPE 

MEAN SERVICE LIFE 

(MINUTES) STD. DEV. 

 

AS RECEIVED 142.10 8.77 

EQUIL. 25% RH 202.79 5.53 

EQUIL. 85% RH 203.06 15.22 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 4 of 14 

4.5. Normal laboratory safety practices must be observed. Please refer to Material Safety 

Data Sheets and the current NIOSH Pittsburgh Health and Safety Program for the proper 

protection and care in handling, storing, and disposing of the chemicals used in this 

procedure. 

 

 4.6. Formaldehyde is considered a probable human carcinogen (Group B1) by EPA. 

 Containers of paraformaldehyde and formaldehyde solution are typically used inside the 

 laboratory fume hood. If there is a release of formaldehyde such as a spill outside the 

 hood, sound an alarm, and any personnel in the laboratory should immediately exit from 

 the building. Formaldehyde is considered hazardous waste by EPA and must be disposed 

 of accordingly. 

4.7. FORMALDEHYDE BENCH TEST FOR PAPR CARTRIDGES 

4.7.1. Resistances and airflows for tight fitting PAPR will be taken before and after 

each test. Airflows only for loose fitting PAPR will be taken before and after 

each test. The standard testing procedures are described in TEB-APR-STP-003, 

TEB-APR-STP-007 and TEB-APR-STP-0012. 

4.7.2. Test conditions as required by 42 CFR 84 

SAMPLE CONDITION EQUILIBRATION CONDITIONS TEST CONDITIONS CONCENTRATION

FOR 6 HOURS PPMV FORMALDEHYDE

TEMP. AIRFLOW R.H. TEMP. AIRFLOW R.H. TEST BREAKTHROUGH

° C

TIGHT 

FITTING

LOOSE 

FITTING % ° C

TIGHT 

FITTING

LOOSE 

FITTING %

LPM LPM LPM LPM

1-3

AS 

RECEIVED NA NA NA NA 25 115 170 50 100 1

4-5

EQUIL. 25% 

R.H. 25 115 170 25 25 115 170 25 100 1

6-7

EQUIL. 85% 

R.H. 25 115 170 85 25 115 170 85 100 1

 Tolerances: 

 

PARAMETER TOLERANCE 

 

25°C ± 2.5°C 

115 LPM ± 1.0 LPM 

170 LPM ± 1.0 LPM 

25% R.H. ± 3% R.H. 

50% R.H. ± 3% R.H. 

85% R.H. +0/-5% R.H. 

100 ppmv ± 10% 

 

NOTES: R.H. levels greater than 85% are difficult to maintain and may cause rapid 

degradation of service life. 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 5 of 14 

Tolerance on accuracy of air flow rates exceeds specification on Miller Nelson control 

unit because flow rates are calibrated for every test. This improves the precision of the 

measurement and allows for the tighter tolerance on short-term drift. 

4.7.3. All equilibrated cartridges will be resealed, kept in a position such that the 

direction of airflow would be horizontal, at room temperature, and testing shall 

begin within 18 hours. 

 4.8. It is particularly important to control the upstream temperature within the specified 

 tolerance range because of the tendency of formaldehyde vapor to polymerize. 

5. PROCEDURE

Note: Reference Section 3 for equipment, model numbers and manufacturers. 

 Work Instructions are to be used in conjunction with standard NIOSH test apparatus. 

5.1. Set up the test equipment as shown in Figure 1. The hygrometer sample line is located 

after the formaldehyde injection point. The paraformaldehyde - water solution will 

increase the RH and must be included in the RH measurement. The hygrometer has a 

platinum coated mirror to resist chemical attack. 

 5.2. Set up the Kin-Tek permeation system with the certified 1 ppm permeation tube for 

analyzer calibration. 

5.2.1. Follow the instruction manual for the permeation system with regard to the 

proper dilution air flow rate, preconditioning of the permeation tube, and the 

correct temperature setting. Preconditioning and calibration may take 48-72 

hours before testing of the respirator can begin. 

5.2.2. Once the concentration has been determined from the permeation system, insert 

the intake tubing from the model 1168 formaldehyde monitor into the stream 

outlet of the permeation system. 

5.2.3. Wait until the reading stabilizes, and adjust the span control to read the 

predetermined calculated concentration of the permeation tube. 

 5.3. Prepare solutions: 

5.3.1. 10%-15% W/V Paraformaldehyde solution: In a 2000 ml beaker containing 

1000 ml distilled water and a stirring bar, add 100-150 g paraformaldehyde. Stir 

and heat the solution to approximately 80-90 ̊C using the heated magnetic stirrer. 

Do not overheat. Place a watch glass over the top of the beaker or cover with 

aluminum foil to prevent excessive water loss, or use a reflux system consisting 

of a flask with a ground glass joint connected to an Alihn condenser. Continue 

stirring and heating until the solution clarifies (about 8-12 hours w/o refluxing, 4-

8 hours w/ refluxing). Filter the solution if not clear after 24 hours. Store in 

the Media Bottle (plastic coated bottle). 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 6 of 14 

5.3.2. 1% starch: Weigh 1g starch and add to 100 ml boiling distilled water. Continue 

boiling until starch has dissolved. Discard when solution becomes cloudy. 

 5.3.3. 0.01N Iodine: Pipet 10 ml of 0.1N iodine into a 100 ml flask. Fill to mark with 

distilled water and invert 10-12 times to ensure complete mixing. Store in amber 

polyethylene bottle. Certified standard solution may also be used. 

 5.3.4. 1% Sodium Bisulfite: Weigh out 5g sodium bisulfite and dissolve in 500 ml 

distilled water. Store in polyethylene bottle. 

 5.3.5. Sodium Carbonate Buffer: Weigh out 40g sodium carbonate and transfer it to a 1 

liter beaker containing a magnetic stir bar. Place the beaker on a magnetic stirrer. 

Add 250 ml of distilled water and stir until fully dissolved. Slowly add 10 ml 

glacial acetic acid while stirring. Dilute to 500 ml. Store in polyethylene bottle. 

 5.3.6. 0.1N Sodium Thiosulfate: Dissolve 24.82g sodium thiosulfate in 1 liter of 

distilled water. Certified standard solution may also be used. 

5.4. Set the airflow to the required level for the sample being tested as per the test 

requirements in paragraph 4.7. Calibrate the total airflow, including any additional flow 

arising from hygrometer flow rates, from the test fixture using the dry test meter. 

5.5. Make sure diverter valve in the system is diverting the challenge concentration airflow to 

discharge and not into the testing chamber. 

5.6. Mount cartridge(s) onto test fixture and place in testing chamber. 

5.7. Fill pump reservoir with formaldehyde solution from the bottle of solution. Insert needle 

from pump to septum tee in airline. 

5.8. Set the high precision pump for delivery of calculated formaldehyde solution to obtain 

100 ppmv at the testing airflow. See appendix 8.2. 

 5.9. Start flow from the high precision pump to the needle. Make sure formaldehyde is 

delivered to the heated vaporizing element. Establish the correct humidity and 

temperature for the sample being tested as per the test requirements in paragraph 4.7. 

Allow 30-40 minutes for equalization of concentration and RH. 

 5.10. Add 10 ml 1% sodium bisulfite solution to the impinger. 

 5.11. Attach Gil-Air 3 sampling pump to intake side of the impinger. Connect outlet side of 

bubbler to Gilibrator. Check 1 lpm flow of the pump pulling through the sodium bisulfite 

solution. This setting will be used to sample the formaldehyde concentration. Remove 

outlet side from Gilibrator. 

 5.12. Connect tubing from the sample side of the impinger into the Gil-Air pump and tubing 

from the inlet side of the gas bubbler into the test concentration. 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 7 of 14 

 5.13. Turn on sampling pump and sample for 30 minutes at 1 lpm. 

 5.14. Shut off vacuum pump and transfer the contents of the impinger into an Erlenmeyer 

flask. Rinse the impinger stem and body and transfer the washings to the flask. 

5.15. Place a stir bar in the flask and place the flask on the magnetic stirrer. Begin stirring. 

5.16. Add 1 ml starch solution. 

5.17. Add 0.1N Iodine dropwise until solution is dark blue. 

5.18. Add 0.1N sodium thiosulfate dropwise until blue color is gone indicating neutralization 

of the excess iodine. 

 5.19. Slowly add 0.01N iodine dropwise from a 50 ml. buret until the first appearance of a faint 

blue color. 

 5.20. Add 25 ml sodium carbonate buffer solution. The blue color should disappear if 

formaldehyde is present. 

 5.21. Record the initial buret reading of the 0.01N Iodine. 

 5.22. Slowly add the 0.01N Iodine until the appearance of a faint blue color. 

 5.23. Record the final buret reading. Calculate the challenge concentration of formaldehyde 

(see 8.2). Adjust syringe pump injection rate if necessary and repeat titration. 

5.24. Note: Alternate direct reading methods for measuring the challenge concentration of 

formaldehyde in this test have been investigated but have been found to be unreliable. 

5.25. Once the test concentration has been established, testing may begin. 

5.26. Weigh the cartridge(s) and record the weight. 

5.27. Measure initial inhalation and exhalation resistances of the cartridge(s) mounted on the 

facepiece as described in TEB-APR-STP-003 and TEB-APR-STP-007. Record values on 

the data sheet. 

5.28. Record the initial weight of the formaldehyde solution bottle and start test. 

5.29. Monitor and record challenge and breakthrough temperatures, challenge RH and 

breakthrough values and times throughout testing. 

5.30. Run test until breakthrough of 1.0 ppmv is observed or minimum service life shown in 

section 6.2 is surpassed by 10%. At end of test, manually turn diverter valve to vent 

position. Weigh and record the final weight of the formaldehyde solution reservoir 

bottle. 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 8 of 14 

5.31. Calculate and record the challenge concentration of formaldehyde (see attachment 8.2). 

5.32. Dismount cartridge(s), weigh and record final weight, and take final inhalation and 

exhalation resistances as described in TEB-APR-STP-003 and TEB-APR-STP-007. 

Measurement of the final inhalation and exhalation resistances is required for 

certification and audit testing. 

5.33. If there is another sample to test, repeat steps 5.6 – 5.31. 

5.34. After all tests are completed for the shift, turn off syringe pump and heater, set 

temperature and humidity to zero on the Miller Nelson system and allow clean air to pass 

through the system for 30 minutes. Purge the breakthrough detector with clean air for 15 

minutes. 

6. PASS/FAIL CRITERIA

6.1. The requirement for passing this test is set forth in 42 CFR Part 84 Subpart G, Section 

84.63(a)(c)(d), Subpart L, Section 84.190(b) and Subpart KK, Section 84.1157(f). 

6.2. Minimum service life requirements for PAPR cartridges are shown below. 

 

Cartridge Test condition Test atmosphere 

Gas or 

vapor 

Concentration 

(p.p.m.v.) 

Flowrate 

(l.p.m.)2

Number of 

tests 

Penetration 1 

(p.p.m.v.) 

Minimum life 

(min.) 

Formaldehyde As received CH2 O 100 115 / 170 3 1.0 50 

Formaldehyde Equilibrated CH2O 100 115 / 170 4 1.0 50 

1

Minimum life will be determined at the indicated penetration. 

2

Test flowrate shall be 115 lpm for tight fitting facepieces and 170 lpm for loose fitting facepieces.

 

7. RECORDS/TEST SHEETS

7.1. Record the test data in a format that shall be stored and retrievable. 

8. ATTACHMENTS

 8.1. Calculation for syringe pump injection rates 

 8.2. Calculation for formaldehyde concentration 

 8.3. Figure 1- Bench Top Set-Up 

 8.4. Data Sheet 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 9 of 14 

8.1. Calculations for formaldehyde delivery – Amersham Syringe Pump 

Calculations for theoretical formaldehyde injection rate 

Molecular weight = 30.0 g/mol 

 1 ppmv = 1.23 mg / m3 @ 25 oC ; 760 mm Hg 

Airflow (L/hr) = Airflow (L / min) x 60 min 

Injection rate (ml/hr) = Conc (ppmv) X 30.0 (g / mol) X Airflow (L/hr) 

 24.45 L/mol x 106 X 1.04 g/ml X (Sol’n. concentration in 

 g/ml) 

For 100 ppmv and 115 lpm, using 12.5% W/V solution: 

 = 100 X 30 g/mol X 115 Lpm X 60 minutes

24.45 X 106 X 1.04 g/ml X 0.125 

= 6.51 ml/hr 

For 100 ppmv and 170 lpm, using 12.5% W/V solution: 

 = 100 X 30 g/mol X 170 Lpm X 60 minutes

24.45 106 X 1.04 g/ml X 0.125 

 = 9.63 ml/hr 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 10 of 14 

8.2. Calculation of Formaldehyde Concentration 

 The formaldehyde equivalent Fe is given by the formula: 

 Fe= ( N I ) x 0.15 mg. 

 .01 

Where NI is the normality of the standardized iodine. This formula is based on the fact that the 

equivalent weight of formaldehyde is 15 g., which means that 1 ml. of 0.01N iodine is equivalent 

to 0.15 mg. of formaldehyde. 

 The amount of formaldehyde in the sample volume collected is given by the formula: 

 Fc = final buret reading - initial buret reading x Femg 

 Fc = total ml. .01 iodine used x 0.15 mg 

 Formaldehyde concentration in ppmv is given by the following formula: 

 ppmv = Fc x 24.45 x 760 x T+273 x 103

 V MW P 298 

 

 Where: 

 V = volume of sample collected (30 Lpm) 

 MW = molecular weight formaldehyde (30.03 g/mole) 

 P = pressure in mm of mercury in the lab 

 T = temperature in  ̊C of the lab 

Assuming that T is equal to 25 ̊C and p is equal to 760 mm mercury, the ppmv formula simplifies 

to: 

 HCHO (ppmv) = Fc x 27.14 assuming volume of sample collected 30 liters 

 HCHO (ppmv) = ml. 0.01 Iodine used x 0.15 mg x 27.14 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 11 of 14 

8.3. Figure 1- Bench Top Set-Up 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 12 of 14 

8.4. Data Sheet 

RB - RESPIRATOR CERTIFICATION TEAM 

 GAS & VAPOR RESPIRATOR TEST DATA SHEET (Ref.33-48,50,62) STP No.: [ ] 

 Task Number: TN- Gas Name: 

Manufacturer: Item Tested: 

RESISTANCE Maximum Allowable Resistance 

 (mm of H2O) 

 Actual Resistance 

 (mm of H2O) 

 Inhalation Exhalation Inhalation Exhalation 

 Test 

Initial Initial 

Final Initial Final 

 Result 

 1

 2

 3

 4

 5

 6

 7

 Overall Results: Pass Fail Comment: 

WEIGHTS WEIGHTS (g) AIRFLOW (Lpm)

 AND 

 AIRFLOWS Test Rate (PAPR Only)

 Test 

Con'd Conc. 

(ppmv) RH% Lpm Initial Final 

 1

 2

 3

 4

 5

 6

 7 

 Overall Results: Pass Fail Comment: 

DATA TABLE Temperature (oC) 

 Test 

 Test 

 Cond. 

 Final 

 Time (min) 

 Leakage 

 (ppmv) 

 Dns

tream 

 Upstr

eam 

 Corrected 

 Time (min) 

 1 

 2 

 3 

 4 

 5 

 6 

 7 

 Overall Results: Pass Fail Comment: 

 Was all testing equipment in calibration throughout all testing: Yes No 

 Signature: Date: 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 13 of 14 

RB - RESPIRATOR CERTIFICATION TEAM Page 2 

GAS & VAPOR RESPIRATOR TEST DATA SHEET (Ref.33-48,50,62) STP No.: [ ] 

 Task Number: TN- Gas Name: 

Manufacturer: Item Tested: 

 

Additional Comments: 

Signature: Date: 
Procedure No. TEB-APR-STP-0039C Revision: 2.0 Date: 24 October 2008 Page 14 of 14 

Revision History 

Revision Date Reason for Revision 

1.0 11 March 2002 Historic document 

1.1 6 June 2005 Update header and format to reflect lab move from Morgantown, WV 

No changes to method 

2.0 1 December 2008 Significant rewrite of RCT-APR-STP-0039. Changes affect form and 

provide clarification of technical content. 

2.1 3 February 2009 Correction to test conditions as specified in table, section 4.7.2. RH 

values in rows two and three changed to 25% and 85 % respectively.