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Evaluation of Decontaminated N95 Respirators

Date Tested: 12/4/2020 – 12/7/2020 

Respirator Model(s): Moldex 1513 Large

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

Integrity with Tensile Testing 

Decontamination Method: UV-C germicidal irradiation, with a UV-C dose ˃ 2 J/cm2 for 1 minute per cycle. 

Decontamination Cycles: 20 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). 

Twenty respirators that were unworn and not subjected to any pathogenic microorganisms were submitted for 

evaluation. This included 15 respirators that were subjected to 20 cycles of the UV-C irradiation 

decontamination process and an additional 5 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 98.38% and 99.97%, 

respectively. All respirators measured efficiencies more than 95%. See Table 1.

Manikin Fit Factor Results: The manikin fit factor showed passing fit factors (≥ 100) for all controls and four out 

of five treated respirators evaluated. See Table 2. 

Strap Integrity Results: The top straps showed a 3.27% decrease in recorded force and the bottom straps 

showed a 3.13% decrease in force. See Table 3. 

Other notes: Treated sample 14’s foam nosepiece was beginning to detach from the respirator, exposing the 

inside of the respirator to the ambient particle concentration during manikin fit testing. This observation can be 

seen in Figure 1A. 

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: Sample Observations 

Fig. 1A. Treated Sample 14 Foam Nosepiece

A
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Figure 2. Laboratory Test Photos

Fig. 2A. Large Static Advanced Headform Fig. 2B. Instron 5943 Tensile Tester Fig. 2C. TSI 8130 Filter Tester

A B C
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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.

Respirator Model, 

Decon Method, # 

of cycles

Treated 

Sample #

Flow Rate

(Lpm)

Initial Filter 

Resistance

(mmH2O)

Initial Percent 

Leakage (%)

Maximum 

Percent 

Leakage (%)

Filter 

Efficiency 

(%)

Moldex 1513 

Large, Controls 

Control 1 85 9.1 0.870 0.870 99.13

Control 2 85 9.9 1.310 1.310 98.69

Control 3 85 10.3 0.749 0.891 99.11

Moldex 1513 

Large, UV-C 

Irradiation, 20 

cycles 

Min Fil Eff: 98.38%

Max Fil Eff: 99.97%

1 85 9.8 0.642 0.700 99.30

2 85 10.9 0.720 0.720 99.28

3 85 9.9 0.698 0.698 99.30

4 85 10.3 0.667 0.675 99.33

5 85 9.5 1.620 1.620 98.38

6 85 10.1 0.423 0.423 99.58

7 85 24.1 0.280 0.028 99.97

8 85 10.1 0.769 0.785 99.22

9 85 10.1 0.569 0.569 99.43

10 85 10.3 0.444 0.444 99.56
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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

Moldex 1513 Large, 

Controls 

Control 4 154 87 96 106

Control 5 200+ 200+ 200+ 200+

Moldex 1513 Large, 

UV-C Irradiation, 20 

cycles 

Static Advanced 

Large Headform 

(Lunar Studios)

11 200+ 200+ 200+ 200+

12 193 93 139 129

13 200+ 192 157 181

14 19 14 14 16

15 194 200+ 185 193

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.

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)

Moldex 1513 Large, Controls 

Control 1 3.195 3.106

Control 2 3.221 3.237

Control 3 3.313 3.040

Control Strap Average 3.243 3.128

Moldex 1513 Large, UV-C 

Irradiation, 20 cycles 

1 3.036 2.947

2 3.244 3.099

3 3.139 3.130

4 3.129 2.944

Decontaminated Strap 

Average 3.137 3.030

% Change

((Deconned - Controls)/ 

Controls)

-3.27% -3.13%