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Evaluation of Decontaminated N95 Respirators 

Date Tested: 10/7/2020-10/9/2020

Respirator Model(s): 3M 1860

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

Integrity with Tensile Testing 

Decontamination Method: Moist heat decontamination at 85°C and 65% RH for 15 minutes using the Cres Cor moist heat 

decontamination cabinet, which involved controlled convected heat and humidity introduced by a built-in water reservoir. 

With specially designed interiors to hold masks and respirators, these conditions demonstrated virus and mycobacterium 

kill at the preset time, temperature and humidity. 

Decontamination Cycles: 1; 3; 5 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). 

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

included 7 respirators that were subjected to 1 cycle of the moist heat decontamination process, 7 respirators subjected to 

3 cycles, 7 respirators subjected to 5 cycles, and an additional 4 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 98.04% and 99.34%, respectively. All 

respirators measured greater than 95%. See Table 1. 

Manikin Fit Factor Results: The manikin fit factor showed passing fit factors (greater than 100) for 6 out of 11 respirators 

(including controls and decontaminated samples) evaluated. See Table 2. 

Strap Integrity Results: No visual degradation of the straps was observed. Inconsistent changes were shown between the 

top and bottom straps. The top straps showed an increase in recorded force for all decontamination cycles. The bottom 

straps showed a decrease in recorded force for 1 and 3 cycles and an increase in recorded force for 5 cycles. See Table 3. 

Other notes: Decontaminated samples had blurring of the printed information on the front of the respirators. Figure 1D 

shows a comparison of this observation between a control sample and a treated sample. The decontaminated samples also 

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. Instron 5934 Tensile Tester Fig 1C. TSI 8130 Filter Tester

Fig 1D. Printed Information-Control Fig 1D. Printed Information-Sample

D D

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 

(%)

3M 1860, controls

Control 1 85 9.0 0.414 0.774 99.23

Control 2 85 8.5 0.446 0.734 99.27

3M 1860, moist 

heat, 1 cycle 

Min Fil Eff: 99.08%

Max Fil Eff: 99.34%

1 85 8.5 0.529 0.921 99.08

2 85 8.4 0.424 0.854 99.15

3 85 8.1 0.297 0.658 99.34

4 85 8.5 0.504 0.882 99.12

3M 1860, moist 

heat, 3 cycles 

Min Fil Eff: 99.05%

Max Fil Eff: 99.25%

1 85 8.5 0.490 0.897 99.10

2 85 9.0 0.337 0.753 99.25

3 85 8.5 0.633 0.948 99.05

4 85 8.3 0.429 0.773 99.23

3M 1860, moist 

heat, 5 cycles

Min Fil Eff: 98.04%

Max Fil Eff: 98.92%

1 85 9.6 1.29 1.29 98.71

2 85 8.0 1.62 1.96 98.04

3 85 8.6 0.806 1.41 98.59

4 85 9.2 0.856 1.08 98.92
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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

3M 1860, controls

Static Advanced 

Medium Headform 

(Hanson Robotics)

Control 3

200+ 160 200+ 185

Control 4

200+ 200+ 200+ 200+

3M 1860, moist 

heat, 1 cycle 

Static Advanced 

Medium Headform

(Hanson Robotics)

5

103 62 93 82

6

130 69 94 91

7

132 90 128 114

3M 1860, moist 

heat, 3 cycles 

Static Advanced 

Medium Headform 

(Hanson Robotics)

5

133 80 127 108

6

48 36 38 86

7

104 72 97 89

3M 1860, moist 

heat, 5 cycles 

Static Advanced 

Medium Headform 

(Hanson Robotics)

5

125 76 111 100

6

114 94 155 116

7

118 76 93 93

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)

3M 1860, controls

Control 1 2.629 2.465

Control 2 2.761 2.479

Control Strap Average 2.695 2.472

3M 1860, moist heat, 1 cycle

1 2.713 2.336

2 2.790 2.417

3 2.743 2.468

4 2.738 2.496

Decontaminated Strap 

Average 2.746 2.429

% Change

((Deconned - Controls)/ 

Controls)

1.89% -1.73%

3M 1860, moist heat, 3 cycles

1 2.760 2.444

2 2.858 2.389

3 2.728 2.476

4 2.680 2.564

Decontaminated Strap 

Average 2.757 2.468

% Change

((Deconned - Controls)/ 

Controls 

2.28% -0.15%

3M 1860, moist heat, 5 cycles

1 2.777 2.482

2 2.664 2.506

3 2.812 2.455

4 2.823 2.546

Decontaminated Strap 

Average 2.769 2.497

% Change

((Deconned - Controls)/ 

Controls 

2.75% 1.02%