Evaluation of Decontaminated N95 Respirators

Date Tested: 4/21/2020-4/22/2020

Respirator Model: 3M 8210

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

Integrity with Tensile Testing

Decontamination Method: DiKlor®-G Sterilization: FFRs subjected to the DiKlor®-G Sterilization Process are loaded into an 

air-tight sterilization chamber with temperature and humidity control and monitoring devices and air sampling devices. 

Before DiKlor®-G is introduced, the temperature and relative humidity inside the chamber must be held continuously at/

above 70°F and 75% RH for at least one hour to precondition contaminated FFRs. These temperature and humidity 

conditions must be maintained and continuously monitored throughout the sterilization process to ensure successful 

sterilization. DiKlor®-G is then introduced in the chamber until a concentration of 100 ppmv has been achieved. Quantitative 

analysis of the DiKlor®-G concentration is regularly performed over the course of the sterilization process. This DiKlor®-G 

concentration is maintained for at least 8 continuous hours, or until 800 CT (ppmv·hrs) has been achieved. After reaching 

the CT target, residual DiKlor®-G is scrubbed from the sterilization chamber before re-entry or retrieval of the sterile FFRs.

Decontamination Cycles: 6 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 6 cycles of the DiKlor-G® sterilization 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 maximum and minimum filter efficiencies were 99.78% and 98.73%, 

respectively. All samples 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. The manikin fit test procedure used in this assessment did not show any detriments in fit associated 

with the decontamination method used. See Table 2. 

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.” 
Figure 1. Laboratory Test Photos

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

the treated samples for the top (15.15%) and bottom (16.04%) straps. 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. 

Other Notes: The nosepiece foam on the 3M 8210 (6 cycles) was discolored (brown color, whereas the control was 

gray).
Table 1. Filter Efficiency Evaluation – 3M 8210, Diklor-G, 6 Cycles

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 8210, 

DiKlor-G, 

6 cycles

Min Fil Eff: 

98.73%

Max Fil Eff: 

99.78%

1

85 7.8 0.901 1.27 98.73

2

85 8.1 0.182 0.329 99.67

3

85 8.7 0.188 0.363 99.64

4

85 8.4 0.114 0.222 99.78

5

85 8.2 0.091 0.974 99.03

6

85 8.4 0.150 0.280 99.72

7

85 8.2 0.124 0.290 99.71

8

85 7.1 0.190 0.367 99.63

9

85 8.2 0.170 0.279 99.72

10 85 7.8 0.154 0.293 99.71

Control 1 85 8.4 0.152 0.324 99.68

Control 2 85 7.9 0.175 0.395 99.61

Control 3 85 7.8 0.193 0.404 99.60
Table 2. Manikin Fit Evaluation, 3M 8210, Diklor-G, 6 Cycles

Manikin Fit Factor of Decontaminated N95s

Treated 

Sample #

mFF Normal 

Breathing 1

mFF Deep 

Breathing

mFF Normal 

Breathing 2

Overall 

Manikin Fit 

Factor

3M 8210, DiKlor-G, 

6 cycles

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+

15 200+ 200+ 200+ 200+

Control 4

200+ 200+ 200+ 200+

Control 5

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.

Table 3. Strap Integrity Evaluation – 3M 8210, DiKlor-G, 6 cycles

Tensile Force in Respirator Straps of Decontaminated N95s

(recorded force values are at 150% strain)

Straps from Treated Sample # Force in Top Strap (N) Force in Bottom Strap (N)

1 6.630 6.345

2 6.562 6.209

3 6.508 6.350

Decontaminated Strap Average 6.567 6.301

Control 1 5.759 5.383

Control 2 5.646 5.476

Control Strap Average 5.703 5.430

% Difference 

((Deconned - Controls) / Controls) 15.15 16.04