Evaluation of Decontaminated N95 Respirators

Date Tested: 6/3/2020 – 6/11/2020

Respirator Model(s): 3M 1860, 3M 1870, 3M V-flex 9105

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

Integrity with Tensile Testing

Decontamination Method: The reprocessing cycle was executed with a Steam Sterilizer using a gravity steam cycle 

consisting of an exposure temperature of 121°C and an exposure time of 30 minutes followed by 30 minutes of subsequent 

drying.

Decontamination Cycles: 3 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).

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

evaluation. This included 21 respirators that were subjected to 3 cycles of the Gravity Steam decontamination 

process and an additional 11 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: 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 3M 1870 

and 3M V-flex 9105 respirators evaluated. The manikin fit factor did not show passing fit factors for the treated 

3M 1860 samples. See Table 2.

Strap Integrity Results: No visual degradation of the straps was observed. Increases in strap force were seen for 

both the top and bottom straps of the 3M 1860. Decreases in strap force were seen for the top and bottom 

straps of the 3M 1870, and inconsistent changes were shown between the top and bottom straps of the 3M Vflex 9105, with the top strap showing a slight increase and the bottom strap showing a decrease in force. 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.” 
Other notes: Treated samples of all models evaluated (3M 1860, 3M 1870, and 3M V-flex 9105) had blurred, 

illegible, respirator information on the outer surface of the respirator. The 3M 1860 had increased roughness on 

the inner surface of the mask, including along the face seal area.

Figure 1. Laboratory Test Photos
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, Gravity 

Steam, 3 cycles

Min Fil Eff: 96.93%

Max Fil Eff: 98.24%

1

85 9.2 2.24 3.40 96.60

2

85 8.8 1.92 3.07 96.93

3

85 8.4 1.08 1.76 98.24

4

85 9.1 1.52 2.54 97.46

5

85 8.7 1.33 2.15 97.85

Control 3 85 8.4 0.503 0.811 99.19

Control 4 85 9.2 0.502 0.805 99.19

3M 1870, Gravity 

Steam, 3 cycles

Min Fil Eff: 97.49%

Max Fil Eff: 98.59%

1

85 8.2 1.80 2.51 97.49

2

85 8.4 1.01 1.41 98.59

3

85 7.8 1.03 1.46 98.54

4

85 8.3 1.56 1.98 98.02

5

85 8.1 1.28 1.81 98.19

Control 3 85 7.8 1.03 1.10 98.90

Control 4 85 7.9 1.53 1.67 98.33

3M V-flex 9105, 

Gravity Steam, 3 

cycles

Min Fil Eff: 98.47%

Max Fil Eff: 98.99%

1 85 4.4 0.962 1.53 98.47

2 85 4.1 0.650 1.01 98.99

3 85 4.8 0.908 1.21 98.79

4 85 5.9 0.803 1.28 98.72

5 85 4.7 0.959 1.46 98.54

Control 3 85 4.6 0.355 0.622 99.38
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, Gravity 

Steam, 3 cycles

Static Advanced 

Medium Headform 

(Hanson Robotics)

6

17 18 19 18

7

21 17 23 20

Control 1 200+ 200+ 200+ 200+

Control 2 200+ 200+ 200+ 200+

3M 1870, Gravity 

Steam, 3 cycles

Static Advanced 

Medium Headform 

(Hanson Robotics)

6

200+ 200+ 200+ 200+

7

200+ 200+ 200+ 200+

Control 1 200+ 200+ 200+ 200+

Control 2 200+ 196 200+ 199

3M V-flex 9105, 

Gravity Steam, 3 

cycles

Static Advanced 

Medium Headform 

(Hanson Robotics)

6

146 124 160 142

7

153 123 116 129

Control 1 159 191 155 167

Control 2 200+ 200+ 200+ 200+

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 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)

3M 1860, Gravity Steam, 3 

cycles

1 3.726 3.488

2 3.822 3.628

3 3.746 3.596

Decontaminated Strap 

Average 3.765 3.571

Control 3 3.771 3.623

Control 4 3.082 3.370

Control Strap Average 3.427 3.497

% Change

((Deconned - Controls) / 

Controls)

9.86% 2.12%

3M 1870, Gravity Steam, 3 

cycles

1 1.452 1.755

2 1.479 1.821

3 1.471 1.640

Decontaminated Strap 

Average 1.467 1.739

Control 3 1.867 1.844

Control 4 1.874 1.843

Control Strap Average 1.871 1.844

% Change

((Deconned - Controls) / 

Controls)

-21.59% -5.69%

3M V-flex 9105, Gravity Steam, 

3 cycles

1 3.105 2.724

2 2.990 2.885

3 2.788 2.987

Decontaminated Strap 

Average 2.961 2.865

Control 3 2.922 3.324

Control Strap Average n/a n/a

% Change

((Deconned - Controls) / 

Controls)

1.33% -13.81%