NIOSH 

Conformity Assessment Interpretation Notice

NIOSH CA 2019-1011

January 2019

 

NIOSH Respirator Approval Program’s use of the NIOSH Bivariate Panel 

during Isoamyl Acetate Fit Testing beginning February 1, 2019

Supersedes 

May 18, 2005 Letter to All Respirator Manufacturers
Document Number

NIOSH CA 2019 -1011

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1 SUMMARY

NIOSH is phasing out the use of the Los Alamos National Laboratory (LANL) Panels and updated

Standard Testing Procedure (STP) TEB-APR-STP-0005-05a-06, Determination of Qualitative Isoamyl

Acetate (IAA) Facepiece Fit, Air-Purifying Respirators, to include use of the NIOSH Bivariate Panel 

(NIOSH Panel). The NIOSH Panel’s anthropometric limits and individual panel cells (1-10) are shown in 

Figure 1. The population cell distribution of the NIOSH Panel is given in Table 1, based on an 18-

member panel. 

Beginning February 1, 2019, NIOSH will implement use of the NIOSH Panel during evaluation of all new 

approvals of air-purifying respirators (half mask and full-facepiece, excluding non-powered, particulate 

only air-purifying respirators). These types of approval projects, accepted in the NIOSH Division 

Electronic Information Management System (DEIMS) on or after February 1, 2019, will be evaluated 

using the NIOSH Panel and the updated STP. A new approval may include a respirator facepiece 

configuration previously approved as part of a different respirator approval configuration. Applicants 

may continue to use the LANL panels to generate pre-submission test data however, NIOSH 

recommends using the procedure outlined in the updated STP. 

Respirators previously approved following testing with LANL Panels continue to be NIOSH-approved 

respirators. When these approvals are submitted for an extension of approval, and the application 

requires human subject testing, the respirator will be evaluated using the NIOSH Panel and if a pass is 

not achieved, the testing will be repeated using the relevant LANL Panel. 

After December 31, 2019, when respirators previously approved following testing with LANL Panels are 

submitted for an extension of approval requiring human subject testing and do not pass the NIOSH 

Panel, they will not be reevaluated using the LANL Panel. 

Certified product audit testing including the use of the anthropometric panels will allow the use of the 

panel used during the original testing for the approval until December 31, 2019. For example, if the

half-facepiece LANL panel was used during the original testing, the half-facepiece LANL panel will be 

used for certified product audit testing until December 31, 2019.

NIOSH Respirator Approval Program’s use of the NIOSH Bivariate Panel during 

Isoamyl Acetate Fit Testing beginning February 1, 2019

 Supersedes the May 18, 2005 Letter to All Respirator Manufacturers
Document Number

NIOSH CA 2019 -1011

Page 3 of 12

Figure 1. The NIOSH Bivariate Panel (NIOSH Panel) includes ten individual member cells defined by 

face width and face length (mm) 

NIOSH Panel – cell number Population distribution (%) Number of test subjects based 

on the population distribution

1 5.5 1

2 5.3 1

3 10.5 2

4 25.0 4

5 7.1 1

6 5.7 1

7 21.3 4

8 8.7 2

9 5.2 1

10 3.5 1

Total number of subjects 18

Table 1: NIOSH Panel cell designations, population distribution, and number of test subjects per cell, 

based on an 18-member panel 

NIOSH Bivariate Panel (NIOSH Panel)
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2 AUTHORITY

42 CFR Part 84, Respiratory Protective Devices

TEB-APR-STP-0005-05a-06, Determination of Qualitative Isoamyl Acetate (IAA) Facepiece Fit, AirPurifying Respirators

3 REFERENCES

Approval of Respiratory Protective Devices, 42 CFR, Part 84

NIOSH May 18, 2005 Letter to All Respirator Manufacturers, Air-Purifying Fit Test Subject Selection

Revised TEB-APR-STP-0005-5a-06

Zhuang, Z., Bradmiller, B., Shaffer, R.: New Respirator Fit Test Panels Representing the Current U.S. 

Civilian Work Force. J. Occup. Environ. Hyg. 4: 647-659 (2007).
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NIOSH CA 2019 -1011

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Appendix A – Background and Supplemental Information 

Prior to Febuary 1, 2019, the NIOSH Respirator Approval Program used human test subjects, 

identified by the LANL Panels (Figures A1 and A2) to assess fit in accordance with 42 Code of Federal 

Regulations Part 84. Use of the LANL Panels to assess fit of air-purifying respirators was included in 

the May 18, 2005 NIOSH Letter to All Respirator Manufacturers, and NIOSH TEB-APR-STP-0005-5a-06. 

Revision 2.0 (20 March 2008), Determination of Qualitative Isoamyl Acetate (IAA) Facepiece Fit, AirPurifying Respirators. 

Figure A1. Los Alamos National Laboratory Full-facepiece Panel, with 10 cell boxes identified

LANL Full-facepiece Panel
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Figure A2. Los Alamos National Laboratory Half-facepiece (mask) Panel, with 10 cell boxes identified

A.1 (Withdrawn) Proposed rulemaking and public comments

The October 30, 2009 NIOSH notice of proposed rulemaking – Total Inward Leakage Requirements for 

Respirators (NIOSH Dockets 36 and 137, RIN 0920-AA33) included a reference to the National 

Academies of Sciences, Engineering, and Medicine study Assessment of the NIOSH Head-and-Face 

Anthropometric Survey of U.S. Respiratory Users. The notice summarized; It is documented in testing 

and agreed by reviewers that the proposed panel represents a substantial improvement over its 

predecessor panel and should be implemented (p 56144, Federal Register, Vol. 74, No. 209). The use of 

the panel in the 2012 NIOSH inter-panel variability study and implementation of the panel in the NIOSH 

Respirator Approval Program was discussed during two webinars completed in July and August of 2013 

(webinar slides and recordings are available in NIOSH Docket 250 – Development of Inward Leakage 

Standards for Half-Mask Air-Purifying Particulate Respirators). 

LANL Half-facepiece (mask) Panel
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Additionally, NIOSH received comments to CDC-2013-0017 NIOSH Docket 250 (p 54432 Federal 

Register, Vol. 78, No. 171, September 4, 2013). Stakeholders responded to questions asked about 

development of an inward leakage standard for half-mask air-purifying particulate respirators and the 

use of anthropometric panels to assess respirator fit. The commenters generally supported using a 

single bivariate panel for performance testing as part of the NIOSH Respirator Approval Program. 

While some responders indicated concerns about the differences between the LANL Panels and the 

NIOSH Panel, they tended to support the use of the more recently developed NIOSH Panel. 

A.2 LANL Panel content TEB-APR-STP-0005-5a-06: Determination of Qualitative Isoamyl Acetate 

(IAA) Facepiece Fit Test, Air-Purifying Respirators

Respirator manufactured in one unique size

According to the NIOSH May 18, 2005 Letter to All Manufacturers, Air-Purifying Fit Test Subject 

Selection ten subjects, one from each cell, were tested and one failure permitted (Table A1). NIOSH

considered retaining this procedure and modifying the STP to include the use of the NIOSH Panel and 

remove the use of the LANL Panels. However, after several discussions about the multiple panel 

distributions and panel sizes used (as given in Tables A1 and A2) NIOSH decided to consider a more 

streamlined approach, and completed a statistical analysis to help identify a better panel size to be 

used when testing any model of respirator. 

Table A1. Number of subjects selected using LANL panels during isoamyl acetate testing of a respirator 

designed and manufactured in one unique size to fit persons with various facial shapes and sizes.

LANL Panel – Cell number Number of Test Subjects

One subject per cell tested, one 

failure allowed. The 

manufacturer may accept an 

unpopulated cell as a failure 

and pass the other 9 cells or the 

program could substitute an 

additional subject from a 

neighboring cell to test if 

needed. 

1 1 subject

2 1 subject

3 1 subject

4 1 subject

5 1 subject

6 1 subject

7 1 subject

8 1 subject

9 1 subject

10 1 subject
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Table A2. Number of subjects selected using LANL panels during isoamyl acetate testing of a respirator 

manufactured in one unique size as designated by the manufacturer. No failures were allowed.

NIOSH Panel – Cell number Number of Test subjects

1 6 subjects total from 

cells 1-4 (1 or 2 from 

each cell to total 6)

2

3

6 subjects total 

from cells 3-8

(1 from each cell 

to total 6)

4

5

6

7 6 subjects total 

from cells 7-10 

(1 or 2 from each 

cell to total 6)

8

9

10

Table A3. Number of subjects selected using LANL panels during isoamyl acetate testing of a respirator 

designed and manufactured in two unique sizes to fit persons with various facial shapes and sizes.

NIOSH Panel – Cell number Number of Test Subjects

1

Small/medium

6 subjects total from cells 1-6

(1 from each cell to total 6)

2

3

4

5

Medium/large

6 subjects total from cells 5-10 

(1 from each cell to total 6)

6

7

8

9

10

NIOSH NPPTL considered the identification and use of overlapping subject cell designations during the 

implementation of the NIOSH Panel. Using the anthropometric data collected [Zhuang 2007], as 

illustrated in Figure A3, the “overlapping cells” identified where a subject may be considered a 

small/medium subject or a medium/large subject. Discussions considered how the new panel “fits” 

over the LANL full-facepiece panel and determined the overlaps may occur in NIOSH Cell 2 (small and 

medium), Cell 5 (medium and large), Cell 6 (small and medium) and Cell 9 (medium and large). 
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Figure A3. NIOSH Panel (outlined in black) and the LANL Panel Full-facepiece (outlined in red) with 

individual subject anthropometric data (given in blue).

A.3 Statistical analysis and determination of consistent sample size and pass/fail criteria.

NIOSH NPPTL completed a statistical analysis to test different sample sizes representative of 5, 10, 12, 

18, and 24-member panels. The simulation study defined the true population fit test fail rate, took 75 

random samples of each distinct sample size, and compared the sample observed average fail rate and 

variance between the sample sizes. 

The true fail rate was varied between 1%, 5%, 15% and the population was set to be 100,000 “people.” 

The true population fail rate means the percentage of the population that would not fit this “sample” 

or “respirator.” For example, in the case of the 15% rate, using 100,000 samples, 15% or 15,000 are 

designated as a “1” or “failure” in the Bernoulli distribution and 85% are designated as a “0” or a nonfailure. Seventy-five distinct random samples were taken for each member panel size studied. 

Member panel sizes varied between 5, 10, 12, 18, and 24. Table 4, column C reports the average 

observed fail rate for each of the sample sizes and each of the true population fail rates over 75 

random samples with replacement. 
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Replacement was used so that the underlying true population fail rate was not effected from sample to 

sample. The analysis observed the means and compared them to the true population fail rate to 

determine how well the sample size estimates the truth over 75 random samples. The data indicated 

each of the sample sizes estimated the true population fail rate across 75 random samples. The 

information in Table A4, column E shows the p values for the comparisons between each of the mean 

fail rates by sample size compared to a sample size of 18. None of the observed fail rates were 

statistically different compared to sample size of 18.

Table A4 column D shows the standard deviation of the observed fail rates across the 75 samples for 

each sample size. This statistic shows the sampling variability and lower variability in the sampling 

distribution is better. As variability decreases there is more confidence that each individual sample 

comes as close as possible to estimating the true population fail rate. 

Using median and mean based homogeneity of variance tests Table A4, column F suggests that the 

variance within sample sizes of 5, 10, and 12 differ significantly from a sample size of 18. A sample size 

of 18 does not differ significantly from a sample size of 24. NIOSH NPPTL concluded there appears to 

be benefits to using a sample size of 18 over a sample size of 5, 10, and 12 and noted no added benefit 

of using a sample size of 24 over 18.
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Table A4. Statistical analysis data used to determine the panel sample size.

A B C D

E

Difference between observed fail 

rates among sample sizes: P value

F

Difference between observed 

variances among sample sizes:

P value

True 

Population 

Fail Rate

Sample 

Size

Observed 

Mean Fail 

Rate 

Across 75 

Samples

Standard 

Deviation of 

Sampling 

Distribution 

Across 75 

Samples

Parametric 

Maximum 

Likelihood 

Estimate

Parametric 

Ordinary 

Least 

Squares

NonParametric

Brown 

ForsytheMedian based 

homogeneity 

of variance 

test

Levene-mean 

based 

homogeneity of 

variance test

1%

5 1.87% 5.86% 0.66 0.36 0.18 0.36 0.01

10 1.07% 3.11% 0.94 0.80 0.26 0.80 0.95

12 0.89% 2.59% 0.85 0.49 0.26 0.49 0.28

18 1.19% 2.63% Reference Group

24 1.00% 2.15% 0.90 0.64 0.90 0.64 0.18

5%

5 6.67% 10.57% 0.41 0.36 0.14 0.17 <0.01

10 5.33% 6.44% 0.96 0.94 0.41 0.06 <0.01

12 6.11% 7.03% 0.65 0.50 0.74 <0.01 <0.01

18 5.41% 5.55% Reference Group

24 6.22% 4.86% 0.60 0.34 0.37 0.73 0.99

15%

5 15.20% 17.35% 0.62 0.73 0.31 <0.01 <0.01

10 15.07% 12.56% 0.69 0.72 0.38 <0.01 <0.01

12 14.78% 11.18% 0.83 0.84 0.99 0.02 0.01

18 14.44% 8.22% Reference Group

24 14.67% 7.48% 0.89 0.86 0.63 0.70 0.45

NIOSH considered pass-fail criteria for the proposed 18-member panel. A mathematical model 

developed by NIOSH Researchers estimated the probability of getting a number of failures in a single 

panel test. The model varied the true population fail rate (1, 5, 10, and 15%), the sample size (5, 10, 

12, 18, and 24-member panels) and the number of failures (0, 1, 2, 3, 4, and 5). 

Based on the analysis, NIOSH NPPTL will allow four failures when testing an 18-member panel during 

evaluations of respirators manufactured in one, two, or three unique sizes, since approximately 100% 

of the individual samples will result in four or fewer failures. Similarly, four failures will be allowed 

when testing a 21 or 24-member panel used during evaluations of respirator designed and 

manufactured in four or five unique sizes, respectively.
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REFERENCES – Appendix A

Hack, A., McConville, J.: Respirator Protection Factors: Part 1 - Development of an Anthropometric 

Test Panel. Am. Ind. Hyg. Assoc. J (39): 970-975 (1978). 

Zhuang, Z., Bradmiller, B., Shaffer, R.: New Respirator Fit Test Panels Representing the Current U.S. 

Civilian Work Force. J. Occup. Environ. Hyg. 4: 647-659 (2007).

NIOSH Docket 036 https://www.cdc.gov/niosh/docket/archive/docket036.html

NIOSH Docket 137 https://www.cdc.gov/niosh/docket/archive/docket137.html

NIOSH DOCKET 250 https://www.cdc.gov/niosh/docket/archive/docket250.html