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-0314 Revision: 1.1 Date: 22 December 2005

DETERMINATION OF LENS FOGGING ON FULL-FACEPIECE CHEMICAL 

BIOLOGICAL RADIOLOGICAL AND NUCLEAR (CBRN) AIR-PURIFYING 

RESPIRATORS STANDARD TEST PROCEDURE (STP) 

1. PURPOSE

1.1 This test establishes the procedures for ensuring that the level of protection 

provided by the degree of lens fogging of the Full Facepiece Chemical Biological 

Radiological and Nuclear (CBRN) Air-Purifying Respirators (APR) submitted for 

Approval, Extension of Approval, or examined during Certified Product Audits, 

meet the minimum certification standards set forth in this Standard Test 

Procedure (STP) as prescribed by 42 CFR, Part 84, Subpart G, Section 

84.63(a)(c)(d); Volume 60, Number 110, June 8, 1995. 

1.2. The purpose of this test is to subject the CBRN APR to a low temperature 

environmental condition in order to test the occurrence and extent of lens fogging 

while the item is worn by a human subject. Respirator lens fogging can be 

defined as the condensation of water vapor on the internal surface of the lenses to 

such a degree that vision becomes impaired. Factors that influence fogging of the 

full facepiece APR lenses or visor include environmental conditions, moisture 

trapping within the facepiece, work intensity, airflow dynamics within the 

facepiece, and the optical surface of the lenses or visor. The procedures described 

herein are intended to test the APR for failure of manufacturers’ design 

characteristics for preventing obstruction of vision due to significant lens/visor 

fogging when subjected to potentially harsh conditions by a user. This procedure 

may be used for other types of Respiratory Protective Devices (RPD): Refer to 

the primary Statement of Standard of that RPD for the Durability Conditioning 

requirements. 

2. GENERAL

This STP describes the Determination of Lens Fogging on Full Facepiece Chemical 

Biological Radiological and Nuclear (CBRN) Air-Purifying Respirators (APR) test in 

sufficient detail that a person knowledgeable in the appropriate technical field can 

conduct the test and determine whether or not the product passes testing.

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3. EQUIPMENT/HUMAN SUBJECTS

3.1 Test Equipment 

3.1.1 Logarithmic Low Acuity Chart 2000 “New ETDRS” or equivalent. 

Double-sided low contrast (2.5% Contrast) Near Vision Chart with 40 cm 

cord to maintain appropriate viewing distance. Chart measures 18 x 23 

cm (7 x 9 in). Figure 1 is an illustration of the Logarithmic Low Acuity 

Chart 2000. 

Figure 1. Logarithmic Low Acuity, 2.5% Contrast Chart 2000 “NEW ETDRS”, Chart 1 and 2; respectively 

3.1.2 Environmental Walk-In Chamber, Model D69 manufactured by Tenny 

Engineering, Inc. or equivalent. The Environmental Walk-In Chamber 

shall possess an adequate light source that will provide between 30 to 50 

foot-candles of task lighting approximately 40 cm from the test subject’s 

eyes in their line of sight. Figure 2 illustrates a Model D69 Environmental 

Walk-In Chamber that can attain temperatures ranging from negative 25o

C 

(-13o

F) to 35oC (95oF), adjustable humidity up to 100% RH and the 

adequate light source. 

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Procedure No. CET-APRS-STP-CBRN-0314 Revision: 1.1 Date: 22 December 2005 Page 3 of 14 

Figure 2. Environmental Walk-In Chamber, Model D69 manufactured by Tenny Engineering, Inc. 

3.1.3. Trackmaster TM 500E Treadmill (JAS Manufacturing) or equivalent. 

Figure 3 illustrates a Trackmaster TM 500E Treadmill machine that test 

subjects will use to perform exercise during the Fogging Test. 

Figure 3. Trackmaster TM 500E Treadmill by JAS Manufacturing 

3.1.4. Stopwatch or timer graduated in specific increments. (photo not shown) 

3.1.5. Light Meter, Model 401036, manufactured by Extech Instruments or 

equivalent. Model 401036 has a range of measurement between 20-20000 

Foot-candles and a resolution of 0.1 foot-candles. Figure 4 is an 

illustration of the Light Meter. 

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Procedure No. CET-APRS-STP-CBRN-0314 Revision: 1.1 Date: 22 December 2005 Page 4 of 14 

Figure 4. Light Meter, Model 401036, by Extech Instruments 

3.1.6. NIOSH or their test representative will supply the following cold weather 

gear: cold weather boots, cold weather trousers, cold weather parkas with 

permanently attached hoods, and cold weather mittens or gloves. The cold 

weather gear shall be available in multiple sizes to accommodate both 

small and large individuals, male or female, and multiple sizes in-between. 

(photo not shown) 

3.2. Human Subjects 

3.2.1. Test administrator(s): Shall have successfully completed the 

CDC/ATSDR Scientific Ethics Training, DHHS/NIH Human Participant 

Protections Education for Research Teams or an equivalent course. Note: 

The NIOSH Human Subject Review Board will deem if courses are 

equivalent. 

3.2.2. Both male and female volunteers between the ages of 18 and 45 will be 

recruited to participate in this test that meet the requirements of the 

currently and subsequently approved NIOSH Human Subject Review 

Board (HSRB), Protocol No. HSRB-02-NPPTL-05XP. Informed consent 

will be obtained from each volunteer upon completion of the Volunteer 

Agreement Affidavit and Volunteer Agreement Affidavit Explanation 

contained in Protocol No. HSRB-02-NPPTL-05XP. 

3.2.3. Since the testing procedures set forth in this test require reading from 

visual acuity charts, volunteer recruits will be excluded from participation 

if they have an unaided visual acuity of 20/40 or worse. However, 

individuals with contact lenses will be allowed to volunteer for testing as 

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Procedure No. CET-APRS-STP-CBRN-0314 Revision: 1.1 Date: 22 December 2005 Page 5 of 14 

long as visual acuity measured with their contacts meets or exceeds the 

20/40 acuity requirement. 

3.2.4. A minimum of two (2) volunteers will be used to complete visual 

performance testing under the low temperature lens fogging condition for 

each respirator system submitted for CBRN APR certification. 

3.3. Required CBRN APR Test Items 

3.3.1. If an APR is available in sizes of small, medium, and large, the 

manufacturer shall supply a minimum of four small, four medium, and 

four large facepieces. 

3.3.2. If an APR is available in two sizes, there shall be four of each size 

available for the testing. 

3.3.3. There shall be four CBRN APRs of each one-size mask system. 

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

precautions described in the current Bruceton Facility Laboratory Safety Manual 

or site-specific procedures that are applicable to the health and safety 

requirements. 

4.2.1. All equipment shall be in a safe operating order, and the test 

administrators shall comply with all equipment safety operating 

procedures. The treadmill must have emergency stop lanyard or other 

equivalent means to automatically stop treadmill movement if the human 

subject falls during the test. 

4.2.2. All electrical equipment cables and wires must be fastened securely to the 

floor by tape or some form of cover to eliminate trip hazards. 

5. PROCEDURES

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Procedure No. CET-APRS-STP-CBRN-0314 Revision: 1.1 Date: 22 December 2005 Page 6 of 14 

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 This procedure describes the Determination of the Lens Fogging Test for ensuring 

that the level of protection provided by the CBRN APR meets or exceeds the 

performance requirements outlined in the Statement of Standard for Chemical, 

Biological, Radiological and Nuclear (CBRN) Full Facepiece Air-Purifying 

Respirator (APR), 7 March 2003 with Revision 2, April 4, 2003. Other types of 

CBRN Respirator Protective Devices (RPD) may be tested for Lens Fogging 

using this procedure: Refer to the primary Statement of Standard for the CBRN 

RPD being tested for the Lens Fogging performance requirements. This 

procedures describes the required sample size, test equipment, test procedure and 

data collection methods for conducting the Determination of the Lens Fogging 

Test on CBRN Full Facepiece RPD. 

5.2 Test Material/Items 

5.2.1 Test Items 

Indicate on the Lens Fogging of Full Facepiece CBRN Air-Purifying 

Respirators Data Sheets in Appendix A the following general pretest 

information about the APR on the test record documentation: 

- NIOSH Application Number 

- Name of Manufacturer 

- Type of RPD being Tested (APR, PAPR, ETC): 

- Model Number of CBRN RPD 

- Model Number of Canister (If Applicable) 

- Date Arrived 

- Date of Fogging Test 

- General Condition of Packaging 

- Appearance of CBRN RPD and Canisters 

- Any Specific Physical Anomalies 

- Type of Test being Conducted 

5.2.2 Number Test Items 

All test items shall be individually numbered without affecting form, fit or 

function using an indelible pen or tagged in a sequence that the number 

can be correlated to the NIOSH application number, manufacturer, and 

model number so it can be tracked throughout the series of tests. For 

example, the number sequence can be LFTS1, LFTS2...; LFTM1, 

LFTM2...; or LFTL1, LFTL2..... In this example, the LFTS1 would 

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Procedure No. CET-APRS-STP-CBRN-0314 Revision: 1.1 Date: 22 December 2005 Page 7 of 14 

indicate a Small sized CBRN APR # 1 that is subjected to the Lens 

Fogging test and LFTL2 would indicate a Large sized CBRN APR #2. 

5.3. Low Temperature Environment 

5.3.1. The environmental test chamber shall be set at minus 21 oC +/- 1o

C (-6 oF 

+/- 2 oF) and be allowed to equalize before preconditioning any of the 

CBRN APR. 

5.3.2. The Treadmill machine shall be set at a speed of 4.8 kilometers per hour 

and at a grade setting of level ground. 

5.3.3. There shall be 2 CBRN APR of each size preconditioned in the chamber at 

the specified temperature [minus 21 oC +/- 1o

C (-6 oF +/- 2 oF)] for 4 

hours. 

5.3.4. Before any visual acuity tests are administered, the antechamber room and 

environmental chamber shall possess an adequate light source that will 

provide between 30 to 50 foot-candles of task lighting approximately 40 

cm (16 in) from the test subject in their line of sight. Measurements shall 

be taken with the Light Meter’s light sensor being placed approximately 

40 cm (16 in) from the human subject’s eye position in their line of sight. 

Measurements shall be taken in the absence of the Visual Acuity Chart. 

The foot-candle values shall be recorded on the Test Data Sheet. 

5.3.5. Prior to entering the chamber, each volunteer will be sized and fitted for 

the test APR per manufacturer’s instructions. Where an individual is 

qualified to wear multiple sizes of the APR, the subject shall select the 

respirator size that provides the most comfortable fit. The test subjects 

shall be trained in the donning and usage of the APR per manufacturer’s 

instructions and be given time to perfect donning techniques under the 

guidance of a test administrator. The subject shall self-don their assigned 

CBRN APR in accordance with the manufacturer’s instructions and the 

Initial Visual Acuity test shall then be administered. Visual acuity shall be 

recorded on the test data sheet using the double-sided low contrast near 

vision chart or an equivalent method. Subjects will be asked to identify 

and read aloud all letters of the smallest line of letters that they are able to 

see when properly positioned 40 cm (16 in) from the test eye chart. If a 

subject correctly identifies all five letters on the chosen line, they will be 

asked to attempt to read the next smallest line of letters on the chart. This 

progression shall continue until a subject is unable to correctly identify at 

least two letters of a single chart line. If a subject is unable to identify all 

five letters of a single line, they will be asked to identify the letters of the 

next largest chart line. 

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5.3.6. Subjects will dress in clean, serviceable, cold weather gear in an airconditioned antechamber room maintained at approximately 22o

C (72oF). 

Test administrators will be available to assist with the donning of the cold 

weather clothing and will ensure that it has been properly donned. 

Volunteers will wear their own clothing under the cold weather gear for 

testing. 

5.3.7. The wear trial will be completed by one subject at a time and will begin as 

the test participant enters the chamber. Upon entering the chamber, the 

subject shall self-don their assigned CBRN APR in accordance with the 

manufacturer’s instructions and a visual acuity test shall then be 

administered. Visual acuity shall be scored using visual acuity 

measurements obtained from the double-sided low contrast near vision 

chart or an equivalent method and shall be recorded as a Visual Acuity 

Score (VAS) value, which is a letter count score. The VAS awards one 

point for each letter read on the visual acuity chart with five letters per 

line. The VAS method assigns a zero score value to a visual acuity of 

20/2000, which results in 50 points for 20/200 and 100 points for 20/20. 

When an individual reads two lines without errors, credit is given for the 

larger lines of the chart that were not actually read. The VAS (VAS #1) 

shall be recorded on the Test Data Sheet contained in Appendix A. 

5.3.8. Subjects will be asked to identify and read aloud all letters of the smallest 

line of letters that they are able to see when properly positioned 40 cm (16 

in) from the test eye chart. If a subject correctly identifies all five letters 

on the chosen line, they will be asked to attempt to read the next smallest 

line of letters on the chart. This progression shall continue until a subject 

is unable to correctly identify at least two letters of a single chart line. If a 

subject is unable to identify all five letters of a single line, they will be 

asked to identify the letters of the next largest chart line. 

5.3.9. The test subject shall be constantly monitored during the test to determine 

that the CBRN APR is functioning satisfactorily and that they are not 

experiencing undue discomfort because of air-flow restrictions or other 

physical changes in the operation of the APR. 

5.3.10. The test participant shall then exercise for five minutes by walking on the 

treadmill at the specified settings. 

5.3.11. Immediately after the exercise, the test participant shall rest for two 

minutes in the standing position at which time a visual acuity test shall be 

administered using the same VAS scoring methods described previously 

in paragraphs 5.3.6 and 5.3.7. The VAS (VAS #2) shall be recorded on 

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Procedure No. CET-APRS-STP-CBRN-0314 Revision: 1.1 Date: 22 December 2005 Page 9 of 14 

the Test Data Sheet. 

5.3.12. The test participant shall then exercise for an additional five minutes by 

walking on the treadmill at the specified settings. 

5.3.13. Immediately after the exercise, the test participant shall remain on the 

treadmill in the standing position at which time another visual acuity test 

shall be administered. Again, the VAS (VAS #3)shall be recorded on the 

Test Data Sheet. 

5.3.14. After completion of the visual acuity test, the subject shall remove the 

CBRN APR and then exit the environmental chamber with the CBRN 

APR. 

5.3.15. The CBRN APR shall normalize in the ambient room temperature for 1 

hour and then be cleaned and sanitized in accordance with instructions 

provided by the manufacturer. 

5.3.16. Once a confirmed seal is attained by the test subject during the pre test 

procedure, test procedure and post test procedure, the test administrator or 

an observer shall not touch the test APR in order to adjust the fit or 

comfort of the APR on the test subject. Standard practice involving hair 

line infractions, nose cup distortion, improper head harness orientation etc 

must be addressed by the applicant’s user instructions since this is a selfdonning and not an expert donning test. 

5.4. Data Analysis 

5.4.1. The average VAS shall be calculated from the VAS obtained after post 

chamber don, after five minutes of exercise, and at the end of final 

exercise period for each individual subject. Record the average VAS (VAS 

#1, VAS #2, and VAS #3) for each individual on the Test Data Sheet and 

assess a pass or fail rating.. 

5.4.2. Record remarks concerning unit operation and test subject’s comments on 

test data sheet. 

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). 

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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. 

(b) 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. 

(c) 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. A candidate CBRN APR in accordance with the Statement of Standard for 

Chemical Biological Radiological and Nuclear (CBRN) Full Facepiece Air 

Purifying Respirators (APR), March 7, 2003 with Revision 2, April 4, 2003 must 

obtain an Average Visual Acuity Score of greater than or equal to 75 points for 

each participant to meet the Low Temperature/ Fogging requirement. Other types 

of CBRN RPD may be tested for Lens Fogging using this procedure: Refer to the 

primary Statement of Standard for that particular CBRN RPD being tested for the 

Lens Fogging requirements. 

7. RECORDS/TEST SHEETS

7.1. All test data shall be recorded on the Lens Fogging Of Full Facepiece CBRN AirPurifying Respirators Data Sheets. 

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 shall be handled as follow: 

7.3.1. If the failure occurs on a new certification application, or extension of 

approval application, send a test report to the Certification, Evaluation and 

Testing Section Chief and prepare the hardware for return to the 

manufacture. 

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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 Certification, 

Evaluation and Testing Section Chief 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 Certification, 

Evaluation and Testing Section Chief, or designee, following the standard 

operating procedures outlined in the Procedure for Scheduling, and 

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Processing Post-Certification Product Audits, RB-SOP-0005-00. 

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Appendix A 

Lens Fogging of Full Facepiece CBRN Air-Purifying Respirators Data Sheets

(Test Data Sheet 1 of 2) 

NIOSH Application Number ______________________________________________ 

Name of Manufacturer ___________________________________________________ 

Type of RPD being Tested (APR, PAPR, ETC): _________________________________

Model Number of CBRN RPD _____________________________________________ 

Model Number of Canister ________________________________________________ 

Date Arrived ___________________________________________________________ 

Date of Fogging Test______________________________________________________ 

General Condition of Packaging ___________________________________________ 

Appearance of CBRN APRs and Canisters___________________________________ 

Any Specific Physical Anomalies ___________________________________________ 

Type of Test being Conducted _____________________________________________ 

Requirements: 

For the CBRN Full Facepiece APR, An Average visual acuity scores for each participant shall be greater 

than or equal to 75 points. 

Other types of CBRN RPD may be tested for Lens Fogging using this procedure: Refer to the primary 

Statement of Standard for that particular CBRN RPD being tested for the Lens Fogging requirements. 

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Lens Fogging of Full Facepiece CBRN Air-Purifying Respirators Data Sheets 

(Test Data Sheet 2 of 2) 

NIOSH Application No. Date: ______________ 

Name of Manufacturer: ________________________________________________________ 

Respirator Type/Model Number: _________________________________________________ 

Requirement: Average visual acuity scores for each test participant shall be greater than or equal to 75 

points. 

Results: 

1. Subject: ; Test Item #_________; Chamber Temp. _ o

C; RH________% 

Task Lighting Requirement:30-50 foot-candles 

Area Foot-candles 

Antechamber Room 

Environmental Chamber 

Comments: 

 

2. Subject: ; Test Item #_________; Chamber Temp. _ o

C; RH________% 

Task Lighting Requirement:30-50 foot-candles 

Area Foot-candles 

Antechamber Room 

Environmental Chamber 

Comments: 

 

Test Administrator Pass Fail ________ 

Time Visual Acuity Score 

Post-chamber don (VAS #1) 

Post 5-min walk (VAS #2) 

End of exercise (VAS #3) 

 Average VAS 

Time Visual Acuity Score 

Post-chamber don (VAS #1) 

Post 5-min walk (VAS #2) 

End of exercise (VAS #3) 

Average VAS 

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Revision History 

Revision Date Reason for Revision 

0 21 September 2004 Historic document 

1.1 22 December 2005 Update header and format 

No changes to method 

 

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