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-0312 Revision: 1.1 Date: 22 December 2005

DETERMINATION OF FIELD OF VIEW FOR FULL FACEPIECE CHEMICAL, 

BIOLOGICAL, RADIOLOGICAL AND NUCLEAR (CBRN) RESPIRATORY PROTECTIVE 

DEVICES (RPD) STANDARD TEST PROCEDURE (STP) 

1. PURPOSE

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

provided by the peripheral field of view (FOV) for full facepiece chemical, 

biological, radiological and nuclear (CBRN) respiratory protective devices (RPD) 

submitted for approval, extension of approval, or examined during certified 

product audits, meets 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) and Federal Register, Volume 60, Number 110, June 8, 

1995. 

The purpose of this test is to quantify the FOV of a CBRN full facepiece RPD by 

measuring the functional visual field of full facepiece respirators with either a 

single visor-type lens or a dual eyepiece lens system. This test method utilizes 

procedures similar to those defined in EN136: 19981

 for measuring peripheral 

FOV, but uses the visual field score (VFS) method described by the American 

Medical Association (AMA) to measure the functional impact of the full 

facepiece on the visual field loss. Visual field loss has the most functional impact 

on visual orientation and an individual’s mobility skills.2 In order to gauge the 

functional impact of such losses as a single score, the AMA Guides to the 

Evaluation of Permanent Impairment, 5th edition3

 utilizes the VFS to estimate the 

consequences rather than the causes of visual field loss.

 

1

 89/686/EEC. European Directive Design. EN136:1998. Minimal Requirements for Overall Masks. 

2

 The International Council of Ophthalmology. Visual Standards-Aspects and Ranges of Vision Loss. Resolution of 

the 29th International Congress of Opthalmology; 2002 April 20; Sydney, Australia. 

3 Guides to the Evaluation of Permanent Impairment, American Medical Association, Chicago. 5th Edition (2002). 

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Multidiscipline emergency responders including firefighters, emergency medical 

technicians, law enforcement officers, decontamination crews and medical staff 

will most likely wear the CBRN RPD. It is vital that these emergency responders 

have an adequate functional field of view while wearing a CBRN full facepiece 

RPD to fulfill their primary operational duties during a response to a terrorist 

event. This test method objectively measures the FOV of a CBRN full facepiece 

RPD to ensure the functional field of view requirement is met as defined in the 

applicable standard. 

2. GENERAL

This STP describes the determination of FOV for full facepiece CBRN RPD test in 

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

conduct the test and determine whether or not the product meets the test requirements. 

3. EQUIPMENT AND MATERIALS

3.1 Test Equipment

3.1.1 Apertometer, Manufactured by INSPEC, as Defined in EN 136:1998 or 

Equivalent. Figure 1 shows a complete apertometer assembly that consists 

of a head form and a graduated spherical shell or hemisphere. Details for 

dimensions of the hemisphere and head form and positioning of the head 

form are available in EN 136:1998. 

Figure 1. Stoll apertometer test fixture 

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3.1.2 Head Form With Light Bulbs Positioned in Each Eye Socket or 

Equivalent. Figure 2 shows the head form equipped with electrical light 

bulbs in the eye sockets with a 67 mm distance between the bulb centers. 

Figure 2. Head form front and side views 

3.1.3 Graduated Spherical Shell or Hemisphere. Figure 3 illustrates the 

graduated spherical shell or hemisphere with numbered radiuses and 

meridians on the convex side of the shell. 

Figure 3. Graduated spherical shell or hemisphere 

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3.1.4. Field of Vision Plotting Chart. A field of vision chart is needed for 

plotting the peripheral field of view that is projected into the test 

assembly. Figure 4 illustrates a plotting chart. 

Figure 4. Field of vision plotting chart

3.1.5. Visual Field Score Scoring Grid Overlay. Figure 5 is an illustration of the 

visual field score scoring grid overlay that is used as an overlay for the 

field of vision chart illustrated in Figure 4. The grid assigns 110 points to a 

field within a radius of 70°. Fifty points are assigned to the central area, up 

to 10° of fixation. The remaining 60 points are assigned to the area beyond 

10°

. The grid points are located along ten meridians (two in each of the 

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upper quadrants, three in each of the lower quadrants) at 25°, 65°, 115°, 

155°, 195°, 225°, 255°, 285°, 315°, and 345° (Fig.5). On each meridian 

dots are placed at 1°, 3°, 5°, 7°, 9°, 15°, 25°, 35°, 45°, 55°, and 65°. In 

order to be used as an overlay, the scoring grid and the field of vision 

plotting chart of Figure 4 must be made to the same scale. 

Figure 5. Visual Field Score Scoring Grid Overlay

3.1.6. Talcum Powder. 

3.2. Human Subjects

No human subjects will be used in the FOV test described in this STP. 

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3.3. Required CBRN RPD Test Items

All facepiece sizes of the CBRN RPD application shall be used in the FOV test; 

however, only the facepiece that anatomically fits the head form the best will be 

tested. Only the associated canister or filter model received with the application 

will be used in the FOV test; in other words, the larger 5” diameter canister used 

for other interoperability tests will not be used in this test. 

4. TESTING REQUIREMENTS AND CONDITIONS

4.1. Any laboratory using this procedure to supply certification test data to NIOSH 

will be subject to the provisions of the NIOSH Supplier Qualifications 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. 

4.2. 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. 

4.3. 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). 

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

precautions described in the current Centers for Disease Control and Prevention 

(CDC) General Laboratory Health and Safety Manual or site-specific procedures 

that are applicable to the health and safety requirements.

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

equipment. 

5. PROCEDURE

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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 procedures describes the FOV test for ensuring that the level of protection 

provided by full facepiece CBRN RPD meets or exceeds the requirements 

outlined in the Statement of Standard for Chemical, Biological, Radiological and 

Nuclear (CBRN) Full Facepiece Air-Purifying Respirator (APR), 7 March 2003. 

Other types of CBRN RPD may be tested for FOV using this procedure: Refer to 

the primary statement of standard for the CBRN RPD being tested for the FOV 

performance requirements. This procedure describes the required sample size, test 

equipment, test procedure, data collection methods and the pass or fail criteria for 

the type of CBRN RDP being tested. 

5.2. Test Items

5.2.1. Test Items. 

Indicate on the test data sheet the following general pretest information 

about the CBRN RPD on the test record documentation: 

- NIOSH application number (TN): 

- Name of manufacturer: 

- Model number of CBRN RPD: 

- Model number of canister (if applicable): 

- Date arrived: 

- Date tested: 

- General condition of packaging: 

- Appearance of CBRN RPD and canisters (if applicable): 

- Any specific physical anomalies: 

- Type of test being conducted: 

5.2.2. Number Test Items. 

All test items shall be individually numbered with a tag 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 S1, M1, and L1. The 

S1 meaning a small CBRN RPD# 1, M1 meaning a medium CBRN 

RPD#1 and L1 meaning a large CBRN RPD#1. 

5.3. Mount Respirator on Head Form

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From all the full facepiece sizes associated with the NIOSH CBRN RPD 

application, select the full facepiece that anatomically best fits the head form of 

the Apertometer by mounting the CBRN RPD on the head form in accordance 

with the manufacture’s donning instructions. Apply talcum powder to the facepiece 

being tested as required to allow easy sliding of the facepiece when adjusting. If 

the CRBN RPD has a chin-cup on the facepiece, first place the head form chin in 

the “cup” of the facepiece and seal facepiece against the face of the head form. 

The headharness straps shall be passed over the head form and adjusted to 

maximize the field of view. The facepiece shall be symmetrically mounted on the 

head form. Perform this procedure with all the full facepieces in order to 

determine which size full facepiece fits best on the test head form. 

5.3.1. Once the correct size RPD is determined, mount the full facepiece onto the 

head form as described in the above paragraph 5.3.1. and in accordance 

with manufacture’s donning instructions. 

5.4. Obtain Performance Data

5.4.1. Illuminate both lights located in the eye-sockets of the head form by 

plugging the cord’s plug into a 110 volt electrical outlet. 

5.4.2. The light from the head form will be projected through the RPD lens 

system onto the apertometer hemisphere. Using the field of vision plotting 

chart (see Fig. 4), transfer the outline of the light projected onto the 

hemisphere’s surface by marking the point at which the light changes to a 

shadow along each of the 36 meridians within the hemisphere. An 

alternate method is to transfer the outline of the light projected onto the 

hemisphere’s surface directly to the visual field score scoring grid overlay 

(see Fig. 5): For alternate method, use visual field score scoring grid 

overlay on page 3 of 3 of the data sheet in Appendix A. 

5.4.3. Once the points have been plotted along each meridian, connect the points 

from one meridian to the next in numerical order. The solid line 

connecting the points represents the peripheral isopter for the CBRN RPD. 

5.4.4. Repeat the procedures identified in Sections 5.3.2. through 5.4.3. to obtain 

the VFS for the other two facepeice fittings. The final VFS will be the 

average of three fittings of the same respirator on the head form. 

5.5. Data Analysis

5.5.1. Properly align the visual field score scoring grid overlay (see Fig. 5) over 

the plotted field of view grid that was transferred onto the field of vision 

plotting chart from Section 5.4.2. NOTE: In order for the visual field 

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score scoring grid overlay (see Fig. 5) to be used as an overlay, it and the 

field of vision plotting chart (see Fig. 4) must be made to the same scale. 

NOTE: If the alternate method described in Section 5.4.2. was used, then 

the solid line drawn that connects the points representing the peripheral 

isopter already exists encompassing the grid points. 

5.5.2. Count the VFS grid points that fall on or inside of the peripheral isopter 

for the CBRN RPD. For example, the points that are contained internal to 

the line of Figure 6 are the VFS grid points that shall be counted. All 

points that are outside of the peripheral isopter shall be ignored. 

5.5.3. Record remarks concerning unit operation and adequacy of the RPD fit to 

the test head form on field of view for full facepiece CBRN RDP Test 

Data Sheet 1 of 2 in Appendix A. 

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Figure 6. Example FOV test results analysis 

23 25 

22 22 

VFS = 92

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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). 

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. 

6.3 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. 

6.4 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 must obtain an average visual field 

score of greater than or equal to 90 to meet the field of view requirement. A 

candidate CBRN (air-purifying or self contained) escape respirator in accordance 

with the Statement of Standard for Chemical, Biological, Radiological, and 

Nuclear (CBRN) (Air Purifying/Self Contained) Escape Respirators, August, 2003

must obtain an average visual field score of greater than or equal to 70 to meet the 

field of view requirement. Other types of CBRN RPD may be tested for FOV 

using this procedure: Refer to the primary statement of standard for that particular 

CBRN RPD being tested for the FOV performance requirements. 

7. RECORDS AND TEST DATA SHEETS

7.1. All test data shall be recorded on the Field Of View for Full Facepiece Chemical 

Biological Radiological Nuclear (CBRN) Respiratory Protective Devices (RPD) 

Data Sheet located in Appendix A. 

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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 follows: 

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 (CET) Team Leader and prepare the hardware for return to the 

manufacture. 

7.3.2. If the failure occurs on hardware examined under an off-the shelf audit, 

the hardware will be examined by the test operator and the CET Section 

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 CET Team Leader, or his designee, following 

the standard operating procedures outlined in the Procedure for 

Scheduling, and Processing Post-Certification Product Audits, RB-SOP0005-00.

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APPENDIX A 

Field of View for Full Facepiece CBRN 

Respiratory Protective Devices (RPD) Data Sheets 

(Test Data Sheet 1 of 3) 

NIOSH Application Number:____________________________________________________ 

Type RPD being Tested:_________________________________________________________ 

Name of Manufacturer:_________________________________________________________ 

Model Number of CBRN RPD:___________________________________________________ 

Model Number of Canister (If Applicable):_________________________________________ 

Date Arrived:__________________________________________________________________ 

Date Tested:___________________________________________________________________ 

General Condition of Packaging:_________________________________________________ 

Appearance of CBRN RPS and Canisters:__________________________________________ 

Any Specific Physical Anomalies:_________________________________________________ 

Remarks concerning unit operation and adequacy of the RPD fit to the test head form 

______________________________________________________________________________ 

______________________________________________________________________________ 

______________________________________________________________________________ 

______________________________________________________________________________ 

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APPENDIX A 

Field of View for Full Facepiece CBRN 

Respiratory Protective Devices (RPD) Data Sheets 

(Test Data Sheet 2 of 3) 

NIOSH Application Number:_____________________________________________________ 

Date:________________________________________________________________________ 

Manufacturer of the RPD:_______________________________________________________ 

Respirator Type (APR, Escape Mask PAPR, Etc):___________________________________ 

Requirement: A full facepiece CBRN gas mask must obtain an average visual field score (VFS) of greater 

than or equal to 90 to meet the field of view requirement. 

A CBRN escape respirator must obtain an average visual field score (VFS) of greater 

than or equal to 70 to meet the field of view requirement. 

Results: 

Number of Points within Peripheral Isopter 

Meridian (o

) Fitting 1 Fitting 2 Fitting 3 

25 

65 

115 

155 

195 

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285 

315 

345 

Total VFS Grid Score 

Average VFS = 

Average VFS = ____________________ 

Comments: 

 

Test administrator signature: ______________________Date:_ Pass _ Fail ___ 

Laboratory supervisor signature: ___________________Date: ___________ 

VFS Grid Score Fitting 1 + VFS Grid Score Fitting 2 + VFS Grid Score Fittings 3

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APPENDIX A 

Field of View for Full Facepiece CBRN 

Respiratory Protective Devices (RPD) Data Sheets 

Visual Field Score Scoring Grid Overlay 

(Test Data Sheet 3 of 3) 

NIOSH Application Number __________________________; RPD Being Tested ___________ 

Name of Manufacturer _______________________________; Date of Testing ______________ 

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Revision History 

Revision Date Reason for Revision 

00 16 September 2004 Historic document 

1.1 22 December 2005 Update header and format 

No changes to method 

 

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