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Evaluation of Decontaminated N95 Respirators 

Date Tested: 8/24/2020 – 8/31/2020

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: Each N95 respirator was exposed to ultrasonically created sub-micron droplets of a 1.06% 

peracetic acid (PAA) solution containing 0.88% hydrogen peroxide, 0.18% acetic acid, and 98.04% reverse osmosis water, all 

at room temperature. The N95 respirators were hung to provide adequate spacing to allow for full surface contact without 

shadowing. The treatment process requires approximately 1 hour and 16 minutes. The N95 respirators were allowed to air 

out until there was no vinegar odor. 

Decontamination Cycles: 1 cycle; 3 cycles; 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). 

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

evaluation. This included 8 respirators that were subjected to 1 cycle of the PAA decontamination process, 8 

respirators subjected to 3 cycles, 8 respirators subjected to 5 cycles, and an additional 6 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: All respirators measured more than 95%. See Table 1. 

Manikin Fit Factor Results: The manikin fit factor showed passing fit factors (greater than 100) for all respirators 

evaluated. See Table 2. 

Strap Integrity Results: No visual degradation of the straps was observed. Treated straps showed increases in 

recorded force at 1, 3, and 5 cycles. See Table 3. 

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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Fig 1A. Static Advanced Headform Fig 1B. Instron 5943 Tensile Tester Fig 1C. 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 

(%)

3M 1860, control

Control 1 85 9.3 0.261 0.534 99.47

Control 2 85 9.9 1.14 1.14 98.86

Control 3 85 9.2 0.332 0.590 99.41

Control 4 85 9.1 0.290 0.568 99.43

3M 1860, PAA,

1 cycle

Min Fil Eff: 98.58%

Max Fil Eff: 99.02%

1

85 9.3 0.577 0.978 99.02

2

85 9.3 0.520 1.11 98.89

3

85 8.8 0.331 1.2 98.80

4

85 9.4 1.2 1.42 98.58

5

85 9.5 0.258 1.0 99.00

3M 1860, PAA, 

3 cycles

Min Fil Eff: 99.08%

Max Fil Eff: 99.49%

1

85 9.1 0.370 0.689 99.31

2 85 9.1 0.362 0.674 99.33

3

85 9.1 0.531 0.925 99.08

4

85 9.6 0.424 0.791 99.21

5

85 9.6 0.265 0.514 99.49

3M 1860, PAA, 

5 cycles 

Min Fil Eff: 98.64%

Max Fil Eff: 99.29%

1

85 8.9 0.380 0.898 99.10

2

85 8.7 0.445 1.02 98.98

3

85 8.5 0.81 1.36 98.64

4

85 9.7 0.33 0.731 99.27

5

85 9.9 0.335 0.707 99.29
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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, control

Static Advanced 

Medium Headform 

(Hanson Robotics)

Control 5

200+ 200+ 200+ 200+

Control 6

200+ 122 200+ 165

3M 1860, PAA,

1 cycle

Static Advanced 

Medium Headform 

(Hanson Robotics)

6

200+ 137 200+ 174

7

123 77 131 104

8

200+ 61 143 106

3M 1860, PAA,

3 cycles

Static Advanced 

Medium Headform

(Hanson Robotics)

6

176 88 200+ 136

7

200+ 177 200+ 192

8

138 83 127 110

3M 1860, PAA,

5 cycles 

Static Advanced 

Medium Headform

(Hanson Robotics)

6

133 82 129 109

7

126 92 140 115

8

200+ 109 200+ 157

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, control 

Control 1 2.607 2.923

Control 2 2.645 2.865

Control 3 2.647 2.964

Control 4 2.701 2.780

Control Strap Average 2.65 2.883

3M 1860, PAA, 1 cycle

1 2.654 2.954

2 2.673 2.897

3 2.836 2.956

Decontaminated Strap 

Average 2.721 2.936

% Change

((Deconned - Controls) / 

Controls)

2.68% 1.84%

3M 1860, PAA, 3 cycles

1 2.622 2.915

2 2.730 3.012

3 2.631 2.947

Decontaminated Strap 

Average 2.661 2.958

% Change

((Deconned - Controls) / 

Controls)

0.42% 2.60%

3M 1860, PAA, 5 cycles

1 2.825 2.791

2 2.697 2.902

3 2.688 3.043

Decontaminated Strap 

Average 2.737 2.912

% Change

((Deconned - Controls) / 

Controls)

3.28% 1.01%