Evaluation of Decontaminated N95 Respirators

Date Tested: 9/17/2020 

Respirator Model(s): 3M 1860

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

Integrity with Tensile Testing 

Decontamination Method: UV-C irradiation produced by low pressure mercury germicidal 254nm lamps that are contained 

within an enclosure designed to protect users from harmful exposure to the UV-C irradiation. The enclosure was a UVConcepts Inc. model UVE (UV-C Enclosure). There are 19 lamps that are strategically positioned within this enclosure: 6 

lamps on each side wall, 4 on the rear wall, and 3 on the ceiling. The interior side of the door has a highly reflective surface, 

and each lamp is surrounded by a curved highly reflective material. This enclosure design minimizes shadowing, which 

allows for 360-degree irradiation exposure to the target subject. The N95 masks are clipped to a rack with the exterior 

surfaces of the masks facing towards the lamps. The masks are also staggered on the rack to provide exposure both on the 

outside and inside of the masks. The cycle is 180 seconds and produces ~1000 mJ/cm2 of UV-C “dose.” This process was 

then repeated 10 times. 

Decontamination Cycles: 10 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). 

Ten respirators that were unworn and not subjected to any pathogenic microorganisms were submitted for evaluation. This 

included 7 respirators that were subjected to 10 cycles of the UV-C (1000 mJ/cm2) irradiation decontamination process and 

an additional 3 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: All respirators measured greater than 95%. See Table 1. 

Manikin Fit Factor Results: The manikin fit factor showed passing fit factors (greater than 100) for all respirators evaluated. 

See Table 2. 

Strap Integrity Results: No visual degradation of the straps was observed. A decrease in recorded force for both the top and 

bottom straps were measured. 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.” 
Figure 1. Laboratory Test Photos

Fig 1A. Static Advanced Headform Fig 1B. Instron 5943 Tensile Tester Fig 1C. TSI 8130 Filter Tester

A B C
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, controls 

Control 1 85 9.1 0.390 0.654 99.35

Control 2 85 9.0 1.42 2.20 97.80

3M 1860, UV-C 

(1000 mJ/cm2), 10 

cycles

Min Fil Eff: 98.97%

Max Fil Eff: 99.61%

1 85 9.4 0.762 1.03 98.97

2 85 10.0 0.311 0.465 99.54

3 85 9.4 0.326 0.529 99.47

4 85 9.7 0.168 0.388 99.61

5 85 10.0 0.944 0.944 99.06
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, control

Static Advanced 

Medium Headform 

(Hanson Robotics)

Control 3 127 99 123 115

3M 1860, UV-C 

(1000 mJ/cm2), 10 

cycles

Static Advanced 

Medium Headform

(Hanson Robotics)

6

200+ 200+ 200+ 200+

7

200+ 101 158 141

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

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, controls 

Control 1 3.074 2.749

Control 2 2.408 2.927

Control Strap Average 2.741 2.838

3M 1860, UV-C (1000 mJ/cm2), 

10 cycles

1 2.775 2.726

2 2.711 2.608

3 2.647 2.842

Decontaminated Strap 

Average 2.711 2.725

% Change

((Deconned – Controls)/ 

Controls)

-1.09% -3.98%