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Evaluation of Decontaminated N95 Respirators 

Date Tested: 9/4/2020 – 9/8/2020 

Respirator Model(s): 3M 1860S 

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

Decontamination Method: Broadband UVC (DECON95). DECON95 is a field deployable, benchtop, conveyorized process 

that uses an electrodeless medium pressure mercury vapor lamp to expose all surfaces of the N95 respirator to broadband 

ultraviolet energy, especially in the UVC band (200-280nm). The respirator is placed on a specially designed carrier and 

placed on a conveyor belt that passes below the lamp. For these assessments, the conveyor was run at 2.4 fpm. At this 

speed, the underside (inside) of the respirator is exposed to 500 mJ/cm2 UVC. 

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 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). 

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

for evaluation. This included 5 respirators that were subjected to 1 cycle of the Broadband UVC 

decontamination process, 5 respirators subjected to 3 cycles, 5 respirators subjected to 5 cycles, and an 

additional 2 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. 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 97.96% and 99.24%, 

respectively. All respirators measured more than 95%. See Table 1. 

Strap Integrity Results: No visual degradation of the straps was observed. The samples treated with 1 cycle of 

Broadband UVC showed mixed results with recorded force between top and bottom straps. The samples treated 

with 3 and 5 cycles of Broadband UVC showed an increase in recorded force for both top and bottom straps. See 

Table 2. 
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Fig 1A. TSI 8130 Filter Tester Fig 1B. Instron 5943 Tensile Tester

A B
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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 1860S, control Control 1 85 11.1 0.335 0.830 99.17%

Control 2 85 11.1 0.294 0.763 99.24%

3M 1860S, 

Broadband UVC, 

1 cycle

Min Fil Eff: 98.58%

Max Fil Eff: 99.24%

1 85 11.7 0.366 1.42 98.58%

2 85 12.1 0.302 0.763 99.24%

3 85 11.5 0.500 1.08 98.92%

4 85 10.8 0.382 0.863 99.14%

5 85 11.7 0.408 1.10 98.90%

3M 1860S, 

Broadband UVC, 

3 cycles

Min Fil Eff: 97.96%

Max Fil Eff: 99.22%

1 85 11.0 0.367 0.785 99.22%

2 85 10.6 0.601 1.32 98.68%

3 85 11.4 0.469 1.04 98.96%

4 85 10.8 0.375 0.807 99.19%

5 85 10.1 1.12 2.04 97.96%

3M 1860S, 

Broadband UVC, 

5 cycles

Min Fil Eff: 98.12%

Max Fil Eff: 98.89%

1 85 11.8 0.654 1.21 98.79%

2 85 11.4 0.664 1.11 98.89%

3 85 12.4 0.621 1.38 98.62%

4 85 11.0 0.745 1.88 98.12%

5 85 11.6 0.473 1.26 98.74%
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Table 2. 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 1860S, control 

Control 1 2.658 2.818

Control 2 2.520 2.758

Control Strap Average 2.589 2.788

3M 1860S, Broadband UVC, 1 

cycle

1 2.617 2.904

2 2.542 2.854

3 2.543 2.821

Decontaminated Strap 

Average 2.567 2.860

% Change

((Deconned - Controls)/ 

Controls)

-0.85% 2.58%

3M 1860S, Broadband UVC, 3 

cycles

1 2.540 2.752

2 2.678 2.760

3 2.562 2.975

Decontaminated Strap 

Average 2.593 2.829

% Change

((Deconned - Controls)/ 

Controls 

0.15% 1.47%

3M 1860S, Broadband UVC, 5 

cycles 

1 2.754 2.979

2 2.709 2.949

3 2.702 3.073

Decontaminated Strap 

Average 2.722 3.000

% Change

((Deconned – Controls)/ 

Controls)

5.14% 7.60%