Evaluation of Decontaminated N95 Respirators 

Date Tested: 4/22/2020 

Respirator Model: 3M 8200

Tests: Filtration with NaCl (modified version of STP-0059) and Strap Integrity with Tensile Testing

Decontamination Method: High energy (10 MeV), high dose rate (3 kGy/s) electron beam irradiation at 25 kGy per 

decontamination cycle. 

Decontamination Cycles: 1, 2, and 3 

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). 

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

evaluation. This included 3 respirators that were subjected to 1 cycle of the electron beam irradiation process, 3 

respirators that were subjected to 2 cycles, 3 respirators that were subjected to 3 cycles, and 3 respirators that 

served as controls. Manikin fit factor testing was not conducted as part of this assessment due to the limited 

number of samples provided. 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. 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; 46.6% and 55.7% (1 cycle); 

47.2% and 51.1% (2 cycles); 47.4% and 50.6% (3 cycles). All samples measured less than 95%. See Table 1. 

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

found in the treated samples for the top (3.49%) and bottom (0.80%) straps subjected to 1 cycle, the top 

(11.78%) and bottom (0.99%) straps subjected to 2 cycles, and the top (14.64%) and bottom (7.19%) straps 

subjected to 3 cycles. 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 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
Table 1. Filter Efficiency Evaluation – 3M 8200, Electron beam irradiation (1,2, and 3 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. 

• 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 (%)

3M 8200

electron beam 

irradiation

1 cycle

Min Fil Eff: 46.6%

Max Fil Eff: 55.7%

1

85 10.4 44.3 44.3 55.7%

2

85 10.0 52.1 52.1 47.9%

3

85 10.1 53.4 53.4 46.6%

3M 8200

electron beam 

irradiation

2 cycles

Min Fil Eff: 47.2%

Max Fil Eff: 51.1%

1

85 10.9 51.3 52.3 47.7%

2

85 10.2 52.8 52.8 47.2%

3

85 11.1 48.9 48.9 51.1%

3M 8200

electron beam 

irradiation

3 cycles

Min Fil Eff: 47.4%

Max Fil Eff: 50.6%

1

85 12.0 49.4 49.4 50.6%

2

85 11.7 51.0 51.0 49.0%

3

85 10.5 52.6 52.6 47.4%

3M 8200

(control)

1

85 12.4 1.33 1.33 98.7%

2

85 10.4 1.06 1.08 98.9%

3

85 11.5 0.96 0.99 99.0%
Table 2. Strap Integrity Evaluation – 3M 8200, Electron beam irradiation (1, 2, and 3 cycles)

Tensile Force in Respirator Straps of Decontaminated N95s

(recorded force values are at 150% strain)

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

1 cycle, sample #1 4.61 5.062

1 cycle, sample #2 4.286 4.881

1 cycle, sample #3 4.446 4.777

Decontaminated Strap Average (1 cycle) 4.447 4.907

2 cycles, sample #1 4.631 4.916

2 cycles, sample #2 4.534 4.67

2 cycles, sample #3 5.244 5.162

Decontaminated Strap Average (2 cycles) 4.803 4.916

3 cycles, sample #1 4.79 5.069

3 cycles, sample #2 4.92 5.332

3 cycles, sample #3 5.069 5.254

Decontaminated Strap Average (3 cycles) 4.926 5.218

Control 1 4.411 5.035

Control 2 4.183 4.701

Control Strap Average 4.297 4.868

% Change – 1 cycle

((Deconned-Control) / Controls) 3.49% 0.80%

% Change – 2 cycles

((Deconned-Control) / Controls) 11.78% 0.99%

% Change – 3 cycles

((Deconned-Control) / Controls) 14.64% 7.19%