PPE CASE

Personal Protective Equipment Conformity Assessment Studies and Evaluations

Performance of Stockpiled Air-Purifying Respirators, Facility Ten of 

Ten: Inhalation and Exhalation Resistance and Filtration Efficiency 

Performance

National Institute for Occupational Safety and Health (NIOSH)

National Personal Protective Technology Laboratory (NPPTL)

Lee A. Greenawald, Susan M. Moore, Patrick L. Yorio

March 1, 2020

In the event of a national emergency, eighteen million U.S. healthcare 

workers may face high-consequence infectious disease exposures

[NIOSH 2017]. Personal protective equipment (PPE), such as gowns, 

gloves, goggles, and respirators, is an important measure within the

infection prevention hierarchy of controls. During public health 

emergencies, the sudden increase in PPE demand may exceed 

supplies for upwards of three months while manufacturers increase 

production [ASTHO 2013; Carias et al. 2015]; [Patel et al. 2017]. For 

example, during the 2009 H1N1 pandemic, local respirator shortages 

were reported and, during the 2016 Ebola outbreak and the first U.S. fatality, there was a 10-200 fold increase in 

PPE orders [DHHS 2012; NIOSH 2018]. To prepare for these shortages, large quantities of PPE are strategically 

stockpiled at hospital, local, state, and federal facilities [NIOSH 1997].

Due to the decision to stockpile PPE, stockpile personnel and decision makers have sought to understand if 

stockpiled PPE is still viable following long-term storage. NIOSH does not require approval holders (i.e. those 

granted the approval from NIOSH) to designate a shelf life for particulate-only air-purifying respirators (APR), 

although some choose to do so and may provide this information on product packaging or online. There is 

limited published data to understand the viability of respirators that have undergone long-term storage with or 

without a designated shelf life. Over the past decade, the Strategic National Stockpile (SNS) and state and local 

stockpile personnel asked NIOSH to evaluate the performance of stockpiled PPE as well as better understand 

storage conditions in U.S. stockpile facilities that store PPE. 

In 2017, NIOSH established a PPE Stockpile Partnership consisting of 1) federal entities and stockpiles; 2) state, 

county, and city stockpiles; 3) hospital-related stockpile entities; and 4) a manufacturer trade association to 

inform the design and execution of an empirical study to evaluate stockpiled APRs. NIOSH obtained samples of 

PPE from geographically dispersed stockpiles with varying storage conditions.

This report details the inhalation/exhalation resistance and filtration performance of N95 filtering facepiece 

APRs collected from Facility Ten of Ten. This facility is a federal stockpile facility. 

NIOSH found that 430 of 430

N95 filtering facepiece 

respirators stockpiled at Facility 

Ten that were 12-13 years old 

maintained their inhalation and 

exhalation resistance and 

filtration performance in 

accordance with NIOSH 

performance standards. 
2

How NIOSH Evaluated Respirators and Storage Conditions

Description of Facility Ten

• NIOSH researchers visited Facility Ten in January 2019 (Figure 1). This facility was located within the U.S. 

Department of Health and Human Services Region 6, representing Arkansas, Louisiana, New Mexico, 

Oklahoma, and Texas. 

Assessment of Storage Conditions

• NIOSH, in conjunction with the PPE Partnership members, developed checklists to document site and 

packaging (i.e. pallet, case, and box) conditions that may impact respirator performance.

• NIOSH documented the following storage conditions: 1) the PPE packaging presence of dust, shrinkwrapping, chemicals, and moisture, 2) exposure to sunlight and direct light; 3) proximity to fans, 

windows, doors, and ventilation systems; 4) damage to pallet and product packaging; and 5) location of 

pallet on storage rack (e.g., top, bottom) and location of PPE product on pallet (e.g., top/not loadbearing, bottom/load-bearing).

Figure 1: NIOSH researchers documented storage practices at Facility Ten such as location and type of 

lighting, pallet stacking practices, and conditions of the flooring, roofing, and exterior walls.

• NIOSH reviewed facility temperature and percent relative humidity (%RH) data provided by Facility Ten

stockpile personnel. This data was collected from January 2014 to February 2019.
3

Collection of Respirator Samples

• Facility Ten’s inventory included APRs that are classified as N95 filtering facepiece respirators (FFRs). 

Samples were collected from five different manufacturing models1

: 1) 3M 1860; Kimberly Clark (KC) 

46827; 3M 8000; 3M 8210; and Gerson 1730 (Table 1). 

• Upon reviewing the detailed APR inventories and storage location by lot within Facility Ten, two 

different manufacturing lots for each model were identified and sampled within Facility Ten. Two lots 

were sampled to evaluate and attempt to account for inter-lot variation. Products were sampled and 

shipped to the NIOSH facility overnight to reduce exposure to non-climate-controlled conditions. 

• Forty-three respirators were tested from each manufacturing lot for inhalation and exhalation

resistance (n=3) and filtration performance testing (n=40)2

.

Selection of Control Respirators

• Control respirators of the same model as those sampled from the facility were purchased from the open 

market to be used as a comparison between stockpiled and new respirators.

Characteristics of Sampled Respirators

• Table 1 provides a summary of the respirator models sampled from Facility Ten. 

Table 1. FFRs Sampled from Stockpile Facility Ten

Model Lot # Year of 

Manufacture

Shelf Life on 

Packaging?

Respirator Age at 

Time of Testing3

Shelf Life 

Status at Time 

of Testing

3M 1860 Lot A 2006 No 13 years

Past 5-year shelf 

life 4 3M 1860 Lot B 2006 No

3M 8000 Lot A 2006 No

13 years

Past 3-year shelf 

life4 3M 8000 Lot B 2006 No

3M 8210 Lot A N/A5 No N/A N/A

3M 8210 Lot B N/A5 No N/A N/A

KC 46827 Lot A 2006 No 12-13 years Past 5-year shelf 

life6 KC 46827 Lot B 2007 No

Gerson 1730 Lot A 2006 No 13 years No shelf life 

Gerson 1730 Lot B 2006 No designated

1 Based on the other nine collaborating stockpiles’ inventories, these six models were sampled in order to compare 

performance within common respirator models when stored under disparate conditions.

2 NIOSH testing requirements state that a minimum of three respirator units must be tested for inhalation and exhalation 

resistance and a minimum of 20 must be tested for filtration efficiency [NIOSH 2018].

3 Testing was completed in 2019. 4 3M designated a five-year shelf life for the 3M 1860 model [3M 2018]. As of February 2020, the 3M 1860 still has a fiveyear shelf life. The 3M 8000 has a three-year shelf life and is no longer produced or sold by 3M. 5 3M was consulted and could not determine the manufacturing date for this lot; it is estimated to be ~2006 based on the 

other APR inventory.

6 KC designated a five-year shelf life for this model [KC 2018]. As of February 2020, this model still has a five-year shelf life.
4

• Twenty-three control respirators were tested for inhalation and exhalation resistance and filtration 

performance. The 3M 1860 controls were manufactured in 2016, the 3M 8000 controls were 

manufactured in 20067

, the KC 46827 controls were manufactured in 2017, and the Gerson 1730

controls were manufactured in 2017. NIOSH testing requirements state that a minimum of three 

respirator units must be tested for inhalation and exhalation resistance. The same three respirators can 

be used for both inhalation and exhalation resistance testing [NIOSH 2018].

• Inhalation and exhalation resistance and filtration performance of the stockpiled and control respirators 

were evaluated using the same Standard Test Procedures (STPs) NIOSH uses for approving respirators 

under 42 Code of Federal Regulations Part 84, “Approval of Respiratory Protective Devices” [NIOSH 

2018] (Table 2). 

• Table 2 describes the method for evaluating the inhalation and exhalation resistance and filtration 

performance of sampled respirators and control respirators.

Table 2. NIOSH Tests Conducted to Evaluate Inhalation and Exhalation Resistance and Filtration Performance. 

NIOSH Standard Test 

Procedures (STPs) Pass/Fail Criteria for APRs

Stockpiled Respirators 

Tested Per 

Manufacturing Lot

Control Respirators 

Tested

STP 3: Exhalation Resistance <25 mm H2O column @ 85 liters 

per minute (LPM) 38 38

STP 7: Inhalation Resistance <35 mm H2O column @ 85 LPM 38 38

STP 59: Particulate Filter 

Efficiency for N95

<5.0% particulate penetration 

(>95.0% filter efficiency) 409 20

What NIOSH Found Through Inspection, Testing, and Evaluation 

Storage Conditions

• Visual Inspections—Dust and damage to product packaging was limited or not observed at Facility Ten; 

an example of the most amount of product case damage is shown in Figure 2. Four product boxes 

showed damage. Of the 430 respirators visually inspected, no concerns were noted.

7 3M 8000 is no longer produced or sold by 3M. 8 NIOSH testing requirements state that a minimum of three respirator units must be tested for inhalation and exhalation 

resistance. The same three respirators can be used for both inhalation and exhalation resistance testing.

9 An increased sample size was used for the stockpiled respirators as opposed to the control respirators to increase the 

precision of the performance estimates investigated.
5

Figure 2: Most amount of damage observed on product cases from Facility Ten.

• Temperature in the facility was controlled; temperature and %RH were monitored. Temperature was 

monitored in 24 locations around the facility, with four temperature probes per location (for a total of 

96 temperature probes). Percent relative humidity was monitored in one location. Fans were activated if 

the temperature reached a set point. Stockpile personnel were automatically alerted if the temperature 

or %RH were close to going out of range. Facility lights had motion sensor capabilities and were on for 

10 minutes each time they were activated. Windows were covered with installation. No evidence of 

excess moisture or chemical spills that persisted beyond immediate mitigation were observed. Pallets 

were generally shrink wrapped around the four pallet sides and across the top. Generally, all pallets 

were separated by a metal rack to reduce weight/load applied to a single pallet. 

• Percent RH (Figure 3) and Temperature (Figure 4)

o At the time of publication, the recommended storage requirements for %RH and temperature 

are

 3M 1860: remain under 80 %RH; remain within -4°F to 86°F [3M 2017]

 3M 80007

: remain under 80 %RH; remain within -4°F to 86°F [3M 2017]

 KC 46827: remain under 60 %RH; remain within 68°F to 77°F [KC 2020]

 Gerson 1730: remain under 80 %RH; remain within -4°F to 95°F [Gerson 2019]

o Facility Ten stockpile personnel provided annual average, minimum, and maximum temperature 

and %RH data for 96 temperature probes and one %RH probe stored within the facility between 

January 2014 – February 2019. 

o The average temperature between the 2014 – 2019 time period was 71.9°F. The average %RH 

between 2014 – 2019 was 44.6%; these averages were within the KC, 3M, and Gerson

recommended temperature and %RH storage conditions.

o 11 of the 15 maximum %RH probe readings provided from 2014 – 2019 exceeded KC’s 

recommended minimum %RH of 60%. As shown in Figure 3, the largest deviation observed was 

23.3 %RH, which was between January 2016 – January 2017.
6

o 75 of the 478 maximum temperature probe readings provided from 2014 – 2019 exceeded KC’s

recommended maximum storage temperature of 77°F. As shown in Figure 4, the largest 

deviation observed was 1.7°F, which was between January 2018 – February 2019 time period.

o 140 of the 478 minimum temperature probe readings provided from 2014 – 2019 went below 

KC’s recommended minimum storage temperature of 68°F. As shown in Figure 4, the largest 

deviation observed was 3.96°F, which was between January 2015 – January 2016.
7

Figure 3: Percent Relative Humidity (% RH) from January 2014 – February 2019 for one %RH probe stored at 

Facility Ten. Data is plotted as minimum, maximum, and average %RH.

Figure 4: Temperatures from January 2014 – February 2019 for 96 temperature probes stored at Facility Ten. 

Data is plotted as minimum, maximum, and average temperatures.
8

Inhalation and Exhalation Resistance

• NIOSH evaluated the inhalation and exhalation resistance for a total of 30 stockpiled and 15 control 

respirators. All stockpiled and control respirators from each model passed these tests (Figure 5).

• Using an analysis of variance (ANOVA), there were no statistically significant differences (defined as 

α<0.05) between each of the FFR controls and FFR stockpiled respirators for inhalation and exhalation 

resistance when averaging across models.

• When comparing the individual respirator models to their respective controls through an ANOVA with 

adjusted, post-hoc multiple comparisons, the following statistically significant differences were found 

with respect to inhalation and exhalation resistance: 1) both KC 46827 stockpiled 2006 Lots A and B

were lower; and 2) both Gerson 1730 stockpiled 2008 Lots A and B were higher. 

• For inhalation resistance, the individual stockpiled respirator with the highest resistance (12.45 mm 

H2O) was below the NIOSH maximum limit for product approval (35 mm H2O allowable maximum). For 

exhalation resistance, the individual stockpiled respirator with the highest resistance (12.19 mm H2O) 

was below the NIOSH maximum limit for product approval (25 mm H2O allowable maximum).
9

Figure 5: Control and stockpiled respirator inhalation (A) and exhalation (B) resistance data. N95 FFRs must have 

an inhalation resistance less than 35 mmH2O and an exhalation resistance less than 25 mmH2O. The pass/fail 

threshold for inhalation (A) and exhalation (B) resistance is shown by the red line. Error bars represent the 99% 

confidence interval and estimate the population parameters. This confidence interval suggests that 99% of any 

repeated samples tested and evaluated from this lot will have a mean between the upper and lower bounds.
10

Filtration Performance

• NIOSH evaluated the particulate penetration efficiency for 400 stockpiled respirators and 100 controls. 

The mean percent particle penetration for each lot of respirators tested is shown in Figure 6.

• None of the individual stockpiled respirators tested exceeded the 5.0% maximum. The highest 

penetration for an individual stockpiled respirator was 4.03% and the highest penetration for an 

individual control respirator was 3.37%. 

• Using an analysis of variance (ANOVA), there was an overall statistically significant difference (defined 

as α<0.05) between the 3M controls (mean penetration=1.86, SD=0.57) and 3M stockpiled respirators 

(mean penetration=1.06, SD=0.72), p<0.001; between Gerson controls (mean penetration=1.04, 

SD=0.17) and Gerson stockpiled respirators (mean penetration=0.81, SD=0.19), p<0.001; and between 

KC controls (mean penetration=1.77, SD=0.45) and KC stockpiled respirators (mean penetration=2.67, 

SD=0.42), p<0.001. 

• When comparing the particle penetration for stockpiled respirator models to their respective controls 

through an ANOVA with adjusted, post-hoc multiple comparisons, each of the comparisons were 

significantly different. 

Figure 6: Control and stockpiled respirator particle filtration performance data. N95 FFRs must have a particle 

penetration of less than 5.0%. Error bars represent the 99% confidence interval and estimate the population 

parameters. This confidence interval suggests that 99% of any repeated samples tested and evaluated from this 

lot will have a mean between the upper and lower bounds.
11

CASE Findings

Findings for the KC 46827 Model:

No failures for inhalation resistance, exhalation resistance, or filtration performance were observed—i.e., the 

performance data suggests that these units would be protective so long as a proper fit is achieved. This model 

currently has a five-year recommended shelf life; Appendix 1 shows a KC letter to end users with shelf life 

information, which states respirators past their shelf life should be discarded [KC 2018]. Thus, these respirators 

tested are past their recommended shelf life. These findings pertain to KC units from Facility Ten and may not be 

applicable to other stockpile facilities and/or under different environmental storage conditions.

Findings for the 3M 1860 and 3M 8210 Models: 

No failures for inhalation resistance, exhalation resistance, or filtration performance were observed—i.e., the 

performance data suggests that these units would be protective so long as a proper fit is achieved. These two

models currently have a five-year recommended shelf life. Appendix 2 shows two 3M letters to end users with 

shelf life and recommended storage condition information [3M 2018, 3M 2020]. Thus, all respirators tested are 

past their recommended shelf life. These findings pertain to 3M units from Facility Ten and may not be 

applicable to other stockpile facilities and/or under different environmental storage conditions.

Findings for the 3M 8000 Model: 

No failures for inhalation resistance, exhalation resistance, or filtration performance were observed—i.e., the 

performance data suggests that these units would be protective so long as a proper fit is achieved. This model 

Is no longer produced and sold by 3M. Appendix 2 shows two 3M letters to end users with shelf life and 

recommended storage condition information [3M 2018, 3M 2020]. Thus, all respirators tested are past their 

recommended shelf life. These findings pertain to 3M units from Facility Ten and may not be applicable to other 

stockpile facilities and/or under different environmental storage conditions.

Findings for the Gerson 1730 Model: 

No failures for inhalation resistance, exhalation resistance, or filtration performance were observed—i.e., the 

performance data suggests that these units would be protective so long as a proper fit is achieved. No shelf 

life was designated for this model by the approval holder. These findings pertain to Gerson units from Facility 

Ten and may not be applicable to other stockpile facilities and/or under different environmental storage 

conditions.

Stockpile Storage Conditions:

The average temperature between the 2014-2019 time period was 71.9°F. The average %RH between 2014 -

2019 was 44.6%; these averages were within the KC, 3M, and Gerson previously described recommended 

temperature and %RH storage conditions. Data points deviated from the KC recommended storage conditions 

for the minimum and maximum temperature and maximum %RH. Stored under these conditions, NIOSH found 

that 430 N95 FFRs evaluated in this study, which were 12-13 years old, maintained their inhalation and 

exhalation resistance and filtration performance (i.e. all sampled respirators were below the NIOSH maximum 

limit as defined by 42 CFR Part 84).
12

NIOSH regulation sets the minimum quality and performance requirements for the approval of respirators 

[NIOSH 1997]. NIOSH does not have requirements for shelf life or storage conditions for particulate-only APRs. 

The approval holder10 (i.e. the entity that is granted the approval from NIOSH) is responsible for understanding 

how their products’ design or performance may be affected by various use or storage conditions and must 

provide instruction for establishing the proper use, storage, and maintenance procedures for their approved 

products, which may include designating a shelf life [NIOSH 2019]. FFR or particulate filter packaging (such as 

the box) often includes NIOSH-approved user instructions, label information, and recommendations on shelf life. 

Additionally, some approval holders also disseminate recommendations related to storage and shelf life through 

resources such as user and web notices. The respirators tested in this study were generally not designed for 

long-term storage.

At this time, we do not have enough information to definitively know the level of protection that may be 

provided by respirators that 1) are stored for prolonged periods of times; 2) are stored under various storage 

conditions; or 3) have exceeded the approval holder’s designated shelf life. Users of respirators that have 

exceeded the designated shelf life should be forewarned to avoid a false sense of confidence; these devices may 

not provide the same level of protection as those that have not exceeded the designated shelf life. We 

recommend contacting the approval holder(s) of the respirators in the stockpile with specific questions 

regarding the use of product beyond the designated shelf life.

NIOSH recommends users contact 3M regarding use of 3M model 8000 respirators.

10 An approval may be granted to a non-manufacturing entity.
13

What Can Stockpile Personnel Do to Learn More about the 

Respirators in their Stockpile?

• Stockpile personnel should check the product information from the approval holder as well as the 

NIOSH Certified Equipment List to remain up-to-date on product storage conditions, shelf-life 

information, and NIOSH approval status. Check NIOSH’s Certified Equipment List to verify the respirator 

model currently maintains its NIOSH approval at 

https://www.cdc.gov/niosh/npptl/topics/respirators/cel/default.html

• Stockpile personnel should work with the approval holder(s) of the stockpiled products with specific 

questions regarding the use of expired product.

• Sign up for NPPTL’s Listserv at https://www.cdc.gov/niosh/npptl/sub-NPPTL.html to receive email 

notifications relevant to PPE.

For more information related to personal protective equipment, visit the NIOSH NPPTL website

https://www.cdc.gov/niosh/npptl/

Get More Information

Find NIOSH products and get answers to workplace safety and health questions:

1-800-CDC-INFO (1-800-232-4636) | TTY: 1-888-232-6348

CDC/NIOSH INFO: cdc.gov/info | cdc.gov/niosh

Monthly NIOSH eNews: cdc.gov/niosh/eNews

All photos courtesy of NIOSH NPPTL.

Disclaimer 

The recommendations in this report are made based on the findings at the stockpile evaluated and may not be 

applicable to other stockpile facilities. 

Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health 

(NIOSH). In addition, citations to websites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or 

their programs or products. Furthermore, NIOSH is not responsible for the content of these websites. All web addresses referenced in 

this document were accessible as of the publication date. 
14 

Suggested Citation 

NIOSH [2020]. PPE CASE: Inhalation and Exhalation Resistance and Filtration Performance of Stockpiled Air-Purifying 

Respirators: Facility Ten of Ten. By Greenawald, L., Moore, S., and Yorio, P. Pittsburgh, PA U.S. Department of Health and 

Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, NPPTL 

Report Number P2020-0110. 

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3M [2018]. 3M Personal Safety Division Letter. St. Paul, MN: The 3M Company. 

https://multimedia.3m.com/mws/media/1430383O/3m-filtering-facepiece-shelf-life-letter.pdf. 

3M [2020]. Frequently Asked Questions: 3M Health Care Particulate Respirator and Surgical Masks Storage Conditions and 

Shelf Life. St. Paul, MN. http://multimedia.3m.com/mws/media/869238O/3m-health-care-particulate-respirator-andsurgical-masks-storage-conditions-and-shelf-life-faq.pdf 

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15

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Appendix 1 [KC 2018]
17

Appendix 2 [3M 2018], [3M 2020]
18
19
20
21