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-0310 Revision: 1.1 Date: 13 December 2005

DETERMINATION OF CBRN FORMALDEHYDE SERVICE-LIFE TEST, AIR-PURIFYING 

RESPIRATORS STANDARD TEST PROCEDURE (STP) 

1. PURPOSE

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

Formaldehyde Service Life Test, Air-Purifying Respirators 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) Full- Facepiece Air- Purifying Respirator (APR) Dated 

March 7, 2003.

2. GENERAL

This STP describes the CBRN Formaldehyde Service Life Test, Air-Purifying Respirators 

Standard Test Procedures 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. 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%).

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 2 of 13 

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

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

3.1.4. Interscan Corporation, Model RM-16-2, formaldehyde detector or 

equivalent. This detector is an electrochemical voltammetric sensor with 

an internal vacuum pump. Detector range: 0 - 1999 ppb, resolution: 1 ppb. 

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

3.1.6. Electronic balance with accuracy of 0.01 grams (g). 

3.1.7. Permeation Tubes of formaldehyde. Used for the calibration of 

formaldehyde detectors. 

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

Used for vaporizing formaldehyde solution. 

3.1.9. 40 Liter glass jug. Used for mixing of formaldehyde vapor. 

3.1.10. Gilibrator, Primary Standard Airflow Calibrator or equivalent.

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

3.1.12. Graduated impinger, 25ml. 

3.1.13. Para-formaldehyde, purified grade. 

3.1.14. Sodium Thiosulfate (granular) or 0.1N certified sodium thiosulfate 

solution. 

3.1.15. Starch, Soluble Potato, Powder. 

3.1.16. Iodine, 0.1N certified solution. 

3.1.17. Sodium Bisulfite, granular. 

3.1.18. Sodium Carbonate, anhydrous powder. 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 3 of 13 

3.1.19. Glacial acetic acid. 

3.1.20. Heated magnetic stirrer and stir bar. 

3.2 Test fixture for mounting canister. 

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® fitting 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 

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 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. 

4.4 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. 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 4 of 13 

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 

disposing of the chemicals and gases used in this procedure.

5. PROCEDURE

5.1 Prepare solutions (must be made at least 24 hours in advance) 

5.1.1 12.5 % Paraformaldehyde solution: In a 2000 ml beaker containing 1000 

ml distilled water and a stirring bar, add 125 g paraformaldehyde. Stir and 

heat the solution to 80EC using the heated magnetic stirrer. Place a watch 

glass over the top of the beaker or cover with aluminum foil to prevent 

excessive water loss. Continue stirring and heating until the solution 

clarifies (about 24 hours). Filter the solution if not clear after 24 hours. 

Store in covered bottle or flask. 

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

calibration purposes use those described in the manufacturer's operation and 

maintenance manuals. 

5.2. Follow the 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. 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 5 of 13 

5.3. After the manufacturer's specified warm-up period, calibrate the formaldehyde 

analyzers using a Kin-Tec generator and permeation tubes to generate 

approximately 1 ppm. 

5.4. Set the high precision pump for delivery of calculated formaldehyde to obtain 500 

ppm at the testing airflow. See appendix 8.2. 

5.5. Set up test equipment as shown in Figure 1 or Figure 2 depending on the test 

parameters in section 6.3. 

5.5.1 For section 6.3.2 test: The airflow is controlled by the Mass Flow 

Controller. Humidity and temperature readings are monitored by a 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. 

5.5.2 For section 6.3.3 and 6.3.4 tests: The airflow, humidity and temperature 

are controlled by the Miller Nelson system. The temperature and humidity 

is monitored a 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. 

5.6. Verify the following equipment is on: 

5.6.1 Air and water (if needed) supplies. 

5.6.2 Miller Nelson Research Flow-Temperature-Humidity Control System. 

5.6.3 Miller Nelson Research Vaporizer system. 

5.6.4 Amersham Biosciences High Precision Pump 

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

fixture using the appropriate dry test meter. 

5.8 Establish the correct humidity and temperature depending on the test parameters 

in section 6.3. 

5.8.1 Fill pump reservoir with distilled H2O. Insert needle from pump to top of 

column. Start the high precision pump flow using the calculated value 

from section 5.3. Allow 15 minutes for equalization system. Make sure 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 6 of 13 

distilled H2O is delivered to the heated vaporizing element. 

5.8.2 Determine the humidity readings for distilled H2O. 

5.8.2.1 For section 6.3.2, the humidity value should be reading 

according to the specification required (25 % ± 5%). If the 

humidity readings are not with in the specification, make 

adjustments to the incoming compressed air or the room 

temperature to establish the specification. 

5.8.2.2 For section 6.3.3 and 6.3.4, the humidity readings can be 

adjusted using the Miller Nelson Controller to the specification 

required (50 % ± 5% or 80% ± 5%). 

5.9 Fill pump reservoir with 12.5 % paraformaldehyde solution, weigh and record 

weight of the reservoir. Insert needle from pump to top of column. Start the high 

precision pump flow. Allow 30-40 minutes for equalization of concentration. 

Make sure formaldehyde is delivered to the heated vaporizing element. 

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

5.11 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. 

5.12 Make sure diverter valve in the system is diverting the challenge concentration 

airflow to discharge and not into the testing chamber. 

5.13 Mount canister onto test fixture and place in testing chamber. 

5.14 Determine the concentration of the formaldehyde vapor being generated. 

5.14.1 Add 10 ml 1% sodium bisulfite solution to two impingers. Connect the 

two impingers together from outlet of one impinger to inlet of second 

impinger. 

5.14.2 Attach Gil-Air 3 sampling pump to intake side of the first impinger. 

Connect outlet side of second impinger 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. 

5.14.3 Connect tubing from the sample side of the first impinger into the GilAir pump and tubing from the inlet side of the second impinger to the 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 7 of 13 

test concentration. 

5.14.4 Turn on sampling pump and sample for 30 minutes at 1 Lpm. 

5.14.5 Shut off sampling pump and transfer the contents of the two impingers 

into an Erlenmeyer flask. Rinse the impinger stem and body and transfer 

the washings to the flask. 

5.14.6 Place a stir bar in the flask and place the flask on the magnetic stirrer. 

Begin stirring. 

5.14.7 Add 1 ml starch solution. 

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

5.14.9 Add 0.1N sodium thiosulfate dropwise until blue color is gone indicating 

neutralization of the excess iodine. 

5.14.10 Slowly add 0.01N iodine dropwise from a 50 ml buret until the first 

appearance of a faint blue color. 

5.14.11 Add 25 ml sodium carbonate buffer solution. The blue color should 

disappear if formaldehyde is present. 

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

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

Calculate the concentration of formaldehyde using the formula in 

Attachments 8.3. Adjust the flow from the high precision pump and 

repeat steps 5.12 through 5.26 if concentration of 500 ppm ± 10% is not 

obtained. If the concentration if correct attach sample line from high 

range detector to the tee in the system. This detector will be used to 

monitor the challenge concentration throughout the length of the test. 

Turn on the strip chart recorder to record the concentration. 

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

5.16 Direct challenge concentration airflow into test chamber. 

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

Monitor and record the upstream and downstream temperatures of the air stream 

throughout testing. 

5.18 Run test until breakthrough of 1000 ppb is observed or minimum service life is 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 8 of 13 

surpassed. Record this data on the test data sheet. 

5.19 Weigh and record on the test data sheet the final weight of test canister. 

5.20 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 Repeat steps 5.7 through 5.20 for each test described in section 6.3. 

5.22 Turn off pump and heating mantel. 

5.23 Allow clean air to purge through system for 10-15 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. Formaldehyde Test for CBRN Canisters 

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

after each test. 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 9 of 13 

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 500 ppm formaldehyde. 

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 oC ± 5 o

C and 500 ppm formaldehyde. 

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 oC ± 5 o

C and 500 ppm formaldehyde. 

Minimum service life for all canisters must be 5 minutes. 

6.3.5 End of service life concentration is 1000 ppb formaldehyde. 

7. RECORDS AND TEST SHEETS

7.1. All test data will be recorded on the FORMALDEHYDE 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 Figure 1- Bench Top Set-Up. 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 10 of 13 

8.2 Calculations for formaldehyde delivery. 

8.3 Data Sheet. 

8.4 Qualitative analysis and calculations for determining concentration of challenge 

formaldehyde vapor. 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 11 of 13 

Attachment 8.2 

Calculations for formaldehyde delivery 

Calculations for formaldehyde. 

1 ppm = 1.23 mg / m3

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

Injection rate (ml/hr) = Conc (ppm) X 30 (g / mol) X Airflow (L/hr) 

 22.4 x 106

 X 1.04 g/ml X 12.5% 

 64 Lpm 100 Lpm 

500 ppm 20 ml/hr 30 ml/hr 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 12 of 13 

Attachment 8.4 

Qualitative Analysis and Calculations for Determining Concentration of Challenge 

Formaldehyde Vapor 

 The formaldehyde equivalent Fe is given by the formula: 

 Fe= ( (N) I ) x 0.15 mg. 

 0.01 

Where (N) I is the normality of the standardized iodine. This formula is based on the fact 

that the equivalent weight of formaldehyde is 15 gm., 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. 0.01 iodine used x 0.15 mg 

 Formaldehyde concentration in ppm is given by the following formula: 

 ppm = 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 EC of the lab 

Assuming that T is equal to 25EC and p is equal to 760 mm mercury, the ppm formula 

simplifies to: 

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

 HCHO (ppm) = ml. 0.01 Iodine used x 0.15 mg x 27.14 

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Procedure No. CET-APRS-STP-CBRN-0310 Revision: 1.1 Date: 13 December 2005 Page 13 of 13 

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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