Evaluation of Decontaminated N95 Respirators

Date(s) Tested: 4/17/2020-4/21/2020

Respirator Model(s): 3M 1860, 3M V-flex 1805, VWR 89201-508

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

Integrity with Tensile Testing

Decontamination Method: ClorDiSys Solutions Minidox-M, Chlorine Dioxide Generator, Concentration: 1 mg/L, RH: 65%, 

Exposure: 720 ppm/hrs (120 min) 

Decontamination Cycles: 4 cycles (3M 1860 and VWR), 1 cycle (3M V-flex 1805) 

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). 

Fifty-nine respirators, of varying manufacturers/models, that were unworn and not subjected to any pathogenic 

microorganisms were submitted for evaluation. This included 30 respirators that were subjected to 4 cycles of 

the Chlorine Dioxide decontamination process, 14 respirators subjected to 1 cycle of the Chlorine Dioxide 

decontamination process, and an additional 15 respirators that served as controls. Figure 1 photos document 

the procedures used. Photos of the samples and information received are shown in Figures 2 and 3. 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 maximum and minimum filter efficiency were as follows; 3M 1860, 4 cycles 

(99.73% and 98.82%); 3M V-flex 1805, 1 cycle (99.80% and 99.50%); VWR 89201, 4 cycles (99.59% and 97.91%).

All samples of all three respirator models had filtration efficiencies measured more than 95%. See Table 1 for 

3M respirators and Table 4 for VWR. 

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

the 3M 1860 (4 cycles) and 3M V-flex 1804 (1 cycle). See Table 2 for 3M respirators. 

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.” 
The manikin fit factor did not show consistent passing fit factors for the VWR 89201 (4 cycles) (range=37-96). 

See Table 5 for VWR respirators. 

The manikin fit test procedure used in this assessment did not show any detriments in fit associated with the 

decontamination method used for the 3M 1860 (4 cycles) and 3M V-flex 1805 (1 cycle), though a significant 

reduction in manikin fit factor was seen in the VWR 89201 (4 cycles). We consider >=100 as the passing criterion 

for Overall Manikin Fit Factor (mFF), as OSHA considers >=100 as a passing Fit Factor (FF). Both control samples 

had an overall mFF >=100, while all five treated samples had an overall mFF<=100. These observations indicate a 

decreased fit of the treated samples as compared to the controls. Small changes in fit factors may be attributed 

to manufacturing variation, variation in donning on the manikin, the decontamination method, or a combination 

of these factors. Larger variations, as seen in this model, may require further research to understand the cause. 

Strap Integrity Results: No visual degradation of the straps was observed. Decreases in recorded force of the 

treated samples were found in the VWR 89201 model for both top (6.15%) and bottom (5.57%) straps. This 

respirator also showed a significant detriment in fit. 

Increases in recorded force of the treated samples were found in the following models for both top and bottom 

straps, respectively; 3M 1860 (15.24% and 18.37%); 3M V-flex 1805 (0.54% and 9.82%). 

While the exact correlation between the force exerted by straps and fit is not well understood, higher force 

values may be associated with a tighter fit of the respirator to the face. Significant reductions in this force would 

be associated with a loss of elasticity of the straps, thereby reducing their ability to create a tight fit. See Table 3 

for 3M respirators and Table 6 the VWR respirator. 

Other Notes: The nosepiece foam on the 3M 1860 (4 cycles) was discolored (brown color, whereas the control 

was gray).
Figure 1. Laboratory test photos from a portion of respirators evaluated
Table 1. Filter Efficiency Evaluation – 3M

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, 

Chlorine 

Dioxide, 4 

cycles

Min Fil Eff: 

98.82%

Max Fil Eff: 

99.73%

1 85 8.4 0.379 0.509 99.49

2 85 8.3 0.247 0.412 99.59

3 85 8.5 0.570 0.751 99.25

4 85 9.3 0.226 1.18 98.82

5

85 8.6 0.530 0.639 99.36

6

85 8.6 0.402 0.525 99.48

7

85 8.5 0.639 0.787 99.21

8

85 9.1 0.294 0.555 99.45

9

85 9.0 0.599 1.14 98.86

10 85 9.1 0.243 0.319 99.68

Control 1 85 9.1 0.379 0.509 99.63

Control 2 85 9.4 0.247 0.412 99.73

Control 3 85 8.7 0.570 0.751 99.69

3M V-flex 1805, 

Chlorine 

Dioxide, 1 cycle

Min Fil Eff: 

99.80%

Max Fil Eff: 

99.50%

1 85 3.7 0.145 0.200 99.80

2 85 4.1 0.153 0.234 99.77

3 85 3.7 0.170 0.269 99.73

4

85 3.8 0.171 0.265 99.74

5

85 3.7 0.174 0.271 99.73

6

85 3.7 0.149 0.239 99.76

7

85 3.7 0.167 0.276 99.72

8

85 3.7 0.213 0.353 99.65

9

85 3.8 0.232 0.293 99.71

10 85 4.0 0.151 0.234 99.77

Control 1 85 3.7 0.321 0.496 99.50

Control 2 85 3.5 0.194 0.337 99.66

Control 3 85 3.9 0.340 0.429 99.57
Table 2. Manikin Fit Evaluations – 3M 

*only 14 samples were received of the 3M V-flex 1805

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.

Manikin Fit Factor (mFF) 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, Chlorine 

Dioxide, 4 cycles

Static Advanced 

Large Headform 

(Lunar Studios)

11 200+ 200+ 200+ 200+

12

200+ 200+ 200+ 200+

13

200+ 200+ 182 194

14

200+ 200+ 200+ 200+

15 200+ 200+ 200+ 200+

Control 4 200+ 200+ 200+ 200+

Control 5

200+ 200+ 200+ 200+

3M V-flex 1805, 

Chlorine Dioxide, 

1 cycle

Static Advanced 

Medium 

Headform 

(Hanson Robotics)

11 200+ 200+ 200+ 200+

12

200+ 200+ 200+ 200+

13

200+ 200+ 200+ 200+

14

200+ 200+ 200+ 200+

15 n/a *

Control 4 200+ 200+ 200+ 200+

Control 5

200+ 200+ 200+ 200+
Table 3. Strap Integrity Evaluation of 3M Respirators

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, Chlorine 

Dioxide, 4 cycles

1 3.529 3.598

2 3.400 3.320

3 3.776 3.988

Decontaminated Strap Average 3.568 3.635

Control 1 3.089 3.068

Control 2 3.102 3.073

Control Average 3.096 3.071

% Change

((Deconned - Control) / Control)

15.24 18.37

3M V-flex 1805, 

Chlorine Dioxide, 1 

cycle

Straps from Treated Sample # Force in Top Strap 

(N)

Force in Bottom Strap 

(N)

1 3.150 3.225

2 2.836 3.160

3 2.918 3.347

Decontaminated Strap Average 2.968 3.244

Control 1 2.981 2.843

Control 2 2.922 3.064

Control Average 2.952 2.954

% Change

((Deconned - Control) / Control)

0.54 9.82
Table 4. Filter Efficiency Evaluation – VWR

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 (%)

VWR 89201, 

Chlorine 

Dioxide, 4 

cycles

Min Fil Eff:

97.91%

Max Fil Eff: 

99.59%

1 85 8.8 1.92 2.09 97.91

2 85 9.4 1.36 1.51 98.49

3 85 9.3 0.553 0.621 99.38

4 85 8.9 1.11 1.79 98.21

5

85 10.2 0.315 0.410 99.59

6

85 9.5 1.01 1.24 98.76

7

85 9.3 0.236 0.307 99.69

8

85 9.0 0.815 0.921 99.08

9

85 9.8 0.452 0.464 99.54

10 85 8.9 0.807 0.944 99.06

Control 1 85 9.0 5.26 5.63 94.37

Control 2 85 8.5 0.743 0.743 99.26

Control 3 85 9.5 4.14 4.16 95.84
Table 5. Manikin Fit Evaluations – VWR

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 less than 100.

Table 6. Strap Integrity Evaluation of VWR Respirator

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)

VWR 89201, Chlorine 

Dioxide, 4 cycles

1 3.702 4.142

2 3.727 3.758

3 4.199 3.902

Decontaminated Strap Average 3.876 3.934

Control 1 4.095 4.074

Control 2 4.164 4.257

Control Average 4.130 4.166

% Change

((Deconned - Control) / Control)

-6.15 -5.57

Manikin Fit Factor (mFF) 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

VWR 89201, 

Chlorine Dioxide, 

4 cycles

Static Advanced 

Medium 

Headform 

(Hanson Robotics)

11 91 61 56 67

12

200+ 61 100 96

13

126 50 70 71

14

62 32 38 41

15 33 34 47 37

Control 4 200+ 64 200+ 117

Control 5

200+ 115 154 149