1

Evaluation of Decontaminated N95 Respirators 

Date Tested: 10/9/2020 – 10/14/2020 

Respirator Model(s): Makrite 9500-N95S 

Tests: Filtration with NaCl (modified version of STP-0059), Manikin Fit Factor with Static Advanced Headform, and Strap 

Integrity with Tensile Testing 

Decontamination Method: Conditioning of the chamber to 45°C over a 20-minute period. Then, a sterilization period of 25 

minutes with vaporized H2O2 (35% concentration). The H2O2 is then inactivated using a catalyst for 60 minutes. 

Decontamination Cycles: 10; 20; 30 cycles 

While decontamination and reuse of FFRs are not consistent with standard and approved usage, these options may need to 

be considered when FFR shortages exist. This assessment was developed to quantify the filtration efficiency and manikin fit 

factor1 of an N95 respirator that has been decontaminated. This assessment is not to determine the effectiveness of the 

decontamination procedure at killing pathogenic microorganisms. The results provided in this report are specific to the 

subset of samples that were provided to NPPTL for evaluation. These results may be used to update the CDC guidance for 

Crisis Capacity Strategies (during known shortages). 

39 respirators that were unworn and not subjected to any pathogenic microorganisms were submitted for evaluation. This 

included 8 respirators that were subjected to 10 cycles of the VHP decontamination process, 8 subjected to 20 cycles, 8 

subjected to 30 cycles, and an additional 15 respirators that served as controls. Figure 1 photos document the procedures 

used. The samples were tested using a modified version of the NIOSH Standard Test Procedure (STP) TEB-APR-STP-0059 to 

determine particulate filtration efficiency. The TSI, Inc. model 8130 using sodium chloride aerosol was used for the filtration 

evaluation. For the laboratory fit evaluation, a static manikin headform was used to quantify changes in manikin fit factor. 

The TSI, Inc. PortaCount® PRO+ 8038 in “N95 Enabled” mode was used for this evaluation. Additionally, tensile strength 

testing of the straps was performed to determine changes in strap integrity. The Instron® 5943 Tensile Tester was used for 

this evaluation. The full assessment plan can be found here. 

Filtration Efficiency Results: The minimum and maximum filter efficiencies were 85.60% and 99.55%, respectively. 13 of the 

15 decontaminated respirators measured more than 95%. 2 of the 15 decontaminated respirators measured efficiencies 

less than 95%. See Table 1. 

Manikin Fit Factor Results: The manikin fit factor showed passing fit factors (greater than 100) for 9 of the 15 respirators 

evaluated (this included controls and treated samples). 1 control and 5 treated samples showed failing fit factors that were 

less than 100. See Table 2. 

Strap Integrity Results: All top straps showed a decrease in recorded force. The bottom straps from the 10 and 30 

decontamination cycles showed a decrease in recorded force and the bottom straps from the 20 decontamination cycles 

showed an increase in recorded force. See Table 3. 

Other notes: Discoloration of the nose foam was observed with the treated samples. Figures 1D and 1E show a comparison 

of this observation between a control sample (grey nose foam) and a treated sample (yellow/brown nose foam). The 

decontaminated samples were also observed to be stiffer and felt rougher to the touch on the inside when compared to the 

controls.

1The American Industrial Hygiene Association defines the Manikin Fit Factor as “An expression related to the amount of leakage measured through the 

face or neck seal of a respirator mounted to a manikin under specified airflow and environmental conditions. If the challenge to the seal is an airborne 

substance, it is the ratio of its airborne concentration outside the respirator divided by the concentration that enters the respirator through the seal. If the 

challenge is airflow or air pressure, conditions and assumptions for quantifying leakage must be specified. Leakage from other sources (e.g., air purifying 

elements) must be essentially zero. The respirator may be mounted to the manikin without sealants; be partially sealed to the manikin; or be sealed to the 

manikin with artificially induced leaks.” 
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Figure 1. Laboratory Test Photos

Fig 1A. Medium Static advanced Headform Fig 1B. TSI 8130 Filter Tester

Fig 1D. Nose Foam-Control (grey) Fig 1E. Nose Foam-Sample (yellow/brown)

1A 1B

1D 1E

E

Fig 1C. Instron 5934 Tensile Tester

1C
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Table 1. Filter Efficiency Evaluation

Notes:

• The test method utilized in this assessment is not the NIOSH standard test procedure that is used for certification

of respirators. Respirators assessed to this modified test plan do not necessarily meet the requirements of STP0059, and therefore cannot be considered equivalent to N95 respirators that were tested to STP-0059.

• BOLD filter efficiencies < 95%.

Respirator Model, 

Decon Method, # 

of cycles

Treated 

Sample #

Flow Rate

(Lpm)

Initial Filter 

Resistance

(mmH2O)

Initial Percent 

Leakage (%)

Maximum 

Percent 

Leakage (%)

Filter 

Efficiency 

(%)

Makrite 9500-

N95S, controls 

Control 1 85 11.4 0.493 0.78 99.22

Control 2 85 11.0 0.651 1.15 98.85

Control 3 85 12.2 0.549 0.702 99.30

Control 4 85 11.6 0.373 0.626 99.37

Control 5 85 15.2 1.420 1.42 98.58

Control 6 85 12.0 0.714 0.851 99.15

Control 7 85 13.0 0.527 0.621 99.38

Control 8 85 13.9 0.531 0.631 99.37

Control 9 85 11.5 0.745 0.822 99.18

Makrite 9500-

N95S, VHP, 10 

cycles 

Min Fil Eff: 96.15%

Max Fil Eff: 99.46%

1 85 10.4 0.922 1.34 98.66

2 85 11.9 0.398 0.58 99.42

3 85 11.8 3.710 3.85 96.15

4 85 11.7 0.409 0.539 99.46

5 85 10.5 0.307 0.604 99.40

Makrite 9500-

N95S, VHP, 20 

cycles 

Min Fil Eff: 85.60%

Max Fil Eff: 99.55%

1 85 15.5 14.40 14.4 85.60

2 85 12.1 2.040 2.24 97.76

3 85 12.3 0.644 0.929 99.07

4 85 12.7 0.381 0.454 99.55

5 85 12.8 6.600 6.89 93.11

Makrite 9500-

N95S, VHP, 30 

cycles 

Min Fil Eff: 98.10%

Max Fil Eff: 99.54%

1 85 10.2 0.965 1.9 98.10

2 85 11.5 0.791 0.907 99.09

3 85 12.2 0.386 0.463 99.54

4 85 12.9 0.498 0.63 99.37

5 85 11.9 0.485 0.527 99.47
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Table 2. Manikin Fit Evaluation

Manikin Fit Factor of Decontaminated N95s

Respirator Model, 

Decon Method, # 

of cycles

Treated

Sample #

mFF Normal 

Breathing 1

mFF Deep 

Breathing

mFF Normal 

Breathing 2

Overall 

Manikin Fit 

Factor

Makrite 9500-

N95S, controls

Static Advanced 

Medium Headform 

(Hanson Robotics)

Control 10 200+ 113 146 145

Control 11 157 68 121 102

Control 12 200+ 117 200+ 162

Control 13 146 66 108 96

Control 14 200+ 112 92 121

Control 15 179 73 102 103

Makrite 9500-

N95S, VHP, 10 

cycles 

Static Advanced 

Medium Headform 

(Hanson Robotics)

6

144 85 145 117

7

151 88 116 113

8

200+ 175 200+ 191

Makrite 9500-

N95S, VHP, 20 

cycles 

Static Advanced 

Medium Headform

(Hanson Robotics)

6

150 47 69 71

7

55 39 41 44

8

200+ 99 97 118

Makrite 9500-

N95S, VHP, 30 

cycles

Static Advanced 

Medium Headform 

(Hanson Robotics)

6

33 25 28 28

7

123 78 76 88

8

45 25 56 37

Notes:

• Per OSHA 1910.134(f)(7), if the fit factor as determined through an OSHA-accepted quantitative fit testing protocol 

is equal to or greater than 100 for tight-fitting half facepieces, then the fit test has been passed for that respirator.

• This assessment does not include fit testing of people and only uses two exercises (normal and deep breathing) on 

a manikin headform. 

• This assessment is a laboratory evaluation using a manikin headform and varies greatly from the OSHA individual 

fit test. This headform testing only includes normal breathing and deep breathing on a stationary (non-moving) 

headform; therefore, fit results from this assessment cannot be directly translated to using the standard OSHAaccepted test. Instead, this testing provides an indication of the change in fit performance (if any) associated with 

the decontamination of respirators. 

• BOLD overall manikin fit factors < 100.
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Table 3. Strap Integrity Evaluation

Tensile Force in Respirator Straps of Decontaminated N95s

(recorded force values are at 150% strain)

Respirator Model, Decon 

Method, # of cycles Straps from Treated Sample # Force in Top Strap (N)

Force in Bottom 

Strap (N)

Makrite 9500-N95S, controls

Control 1 3.450 4.068

Control 2 3.891 3.920

Control 3 3.910 4.110

Control 4 3.567 3.679

Control 5 3.933 3.814

Control 6 3.963 3.559

Control 7 3.968 3.789

Control 8 3.889 3.883

Control 9 4.027 3.884

Control Strap Average 3.844 3.856

Makrite 9500-N95S, VHP, 10 

cycles 

1 3.521 3.716

2 3.626 3.895

3 3.588 3.694

4 3.605 3.864

5 3.613 3.609

Decontaminated Strap 

Average 3.591 3.756

% Change

((Deconned - Controls)/ 

Controls)

-6.59% -2.60%

Makrite 9500-N95S, VHP, 20 

cycles 

1 3.572 3.835

2 3.580 3.798

3 3.707 3.925

4 3.817 4.061

5 3.765 3.686

Decontaminated Strap 

Average 3.688 3.861

% Change 

((Deconned - Controls)/ 

Controls)

-4.05% 0.13%

Makrite 9500-N95S, VHP, 30 

cycles 

1 3.213 3.350

2 3.560 3.384

3 3.630 3.455

4 3.581 3.464

5 3.580 3.384

Decontaminated Strap 

Average 3.513 3.407

% Change

((Deconned - Controls)/ 

Controls 

-8.62% -11.63%