PPE CASE

Personal Protective Equipment Conformity Assessment Studies and Evaluations

Performance of Stockpiled Air-Purifying Respirators, Facility Three

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 Three of Ten. This facility is a county stockpile facility.

NIOSH found that 256 of 258 N95 

filtering facepiece respirators 

stockpiled at Facility Three that 

were 8-11 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 Three

• NIOSH researchers visited Facility Three in December 2017 (Figure 1). This facility was located within the 

U.S. Department of Health and Human Services Region 4, representing Alabama, Florida, Georgia, 

Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee. 

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 Three such as location and type of 

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

• NIOSH collected facility temperature and percent relative humidity (%RH) data by placing two data 

loggers in the facility: Data Logger 1 was placed in a non-climate controlled room adjacent to where the 

respirators used to be stored. Data Logger 2 was placed in the storage room where the respirators are 

currently stored; this room is only recently temperature-controlled, thus the majority of the respirator’s 

storage life within Facility Three has been under non-climate controlled conditions, represented by Data 

Logger 1. This data was collected in 60-minute intervals from October 2017 to November 2018 (Data 

Logger 1) and January 2018 to January 2019 (Data Logger 2). Data Logger 2 was placed after Data Logger 

1 as a result of a decision to collect environmental conditions in the storage room.
3

Collection of Respirator Samples

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

NIOSH collected samples for two APR models stockpiled at this location1

: 1) 3M 1860 (two different 

manufacturing years) and 2) Kimberly Clark (KC) 46827 (one manufacturing year) (Table 1). 

• A detailed APR inventory was not available for Facility Three. two different manufacturing lots for each 

model were identified and sampled within Facility Three. 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 Three. 

Table 1. FFRs Sampled from Stockpile Facility Three

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 11 years

Past 5-year shelf 

life4 3M 1860 Lot B 2006 No

3M 1860 Lot A 2009 No

8 years

Past 5-year shelf 

life4 3M 1860 Lot B 2009 No

KC 46727 Lot A 2006 No 11 years Past 5-year shelf 

life5 KC 46727 Lot B 2006 No

Evaluation of Inhalation and Exhalation Resistance and Filtration Performance

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

performance. The KC 46827 controls were manufactured in 2017 and the 3M 1860 controls were 

manufactured in 2018. 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].

1 Based on the other nine collaborating stockpiles’ inventories, these three 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 2017. 4 In 2013, 3M designated a five-year shelf life for the 3M 1860 model [3M 2018]. As of February 2020, this model still has a 

five-year shelf life. 5 In 2014, KC designated a five-year shelf life for the KC 46727 model [KC 2018]. As of February 2020, this model still has a 

five-year shelf life.
4

• 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) 36 36

STP 7: Inhalation Resistance <35 mm H2O column @ 85 LPM 36 36

STP 59: Particulate Filter 

Efficiency for N95

<5.0% particulate penetration 

(>95.0% filter efficiency) 407 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 

Three. Product boxes were outside of the original packaging (i.e. case; Figure 2A), and product cases 

were open (Figure 2B). Five boxes had damage (Figure 3). Of the 258 respirators visually inspected, only 

one concern was noted, which was damage to the metal nose bridge (Figure 4).

Figure 2: Product boxes outside of product cases (A) and product cases open (B) in Facility Three

6 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. 7 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 3: Slight damage to product boxes from Facility Three

Figure 4: Most amount of product damage observed from Facility Three (the respirator is affixed to a test plate 

via beeswax).

• Facility lights were off when not in use and no windows allowed sunlight to enter the facility. Some 

moisture damage was observed on the ceiling, but not directly above the respirator products. Products 

were stored in—or on top of—Rubbermaid containers.

• Percent RH (Figure 5) and Temperature (Figure 6)

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]

 KC 46727: remain under 60 %RH; remain within 68°F to 77°F [KC 2020]
6

o The average temperature for Data Loggers 1 and 2 were 67.8°F and 75.0°F, respectively. The 

average %RH for Data Loggers 1 and 2 were 54.7% and 40.2%, respectively. These averages are

within the 3M and KC recommended temperature and %RH storage conditions.

o Data Logger 1 (representing historical climate conditions for the products sampled): For the 3M 

1860 model, no temperature data points deviated from the recommended storage conditions. 

For the KC 46727 respirator model, 53% of data points were below 68°F and 38% were above 

77°F. For %RH, 1.5% of data points deviated from 3M’s recommended storage conditions, and 

46% of data points deviated from KC’s recommended conditions.

o Data Logger 2 (representing current climate conditions for the products sampled): For the 3M 

model, no temperature data points deviated from the recommended storage conditions. For the 

KC 46727 respirator model, 8% of data points were below 68°F and 23% of data points were 

above 77°F. For %RH, 11.5% of data points deviated from 3M’s recommended storage 

conditions, and 12% of data points deviated from KC’s recommended conditions.

o Some respirators from Facility Three may have been previously stored and deployed from a 

federal SNS facility. Although the current tracking process does not allow for retrieval of the 

historical location(s) and environmental conditions for these sampled products, subsequent 

discussions with SNS leadership suggest that SNS storage conditions met the recommended

conditions.
7

Figure 5: Percent relative humidity (%RH) from October 2017 – January 2019 (Data Logger 1) and January 2018 –

January 2019 (Data Logger 2) stored at Facility Three. Data is plotted as a 50-point moving average for 

visualization purposes. Maximum and minimum temperatures reported are noted for each data logger.
8

Figure 6: Temperatures from October 2017 – January 2019 (Data Logger 1) and January 2018 – January 2019 

(Data Logger 2) stored at Facility Three. Data is plotted as a 50-point moving average for visualization purposes.

Maximum and minimum temperatures reported are noted for each data logger.
9

Inhalation and Exhalation Resistance

• NIOSH evaluated the inhalation and exhalation resistance for a total of 18 stockpiled and 6 control 

respirators. All stockpiled and control respirators from each model passed these tests (Figure 7).

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

α<0.05) between 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, there were no statistically significant differences detected. The 

mean inhalation and exhalation resistance values are shown in Figure 7.

• For inhalation resistance, the individual stockpiled respirator with the highest resistance (12.19 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 (10.40 mm H2O) 

was below the NIOSH maximum limit for product approval (25 mm H2O allowable maximum).
10

Figure 7: 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.
11

Filtration Performance

• NIOSH evaluated the particulate penetration efficiency for 240 stockpiled respirators and 40 controls. 

• Two individual 3M 1860 stockpiled respirators tested exceeded the 5.0% maximum. These respirators 

were from two different production lots: one respirator was manufactured in 2006, and the second 

respirator was manufactured in 2009. The highest penetration for an individual stockpiled respirator 

was 11.00% (3M 1860) and the highest penetration for an individual control respirator was 4.93% (KC 

46727). 

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

α<0.05) between the FFR controls and FFR stockpiled respirators for filtration 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 

detected: 1) 3M 1860 stockpiled 2006 Lot B had a higher penetration; and 2) 3M 1860 stockpiled 2009 

Lot A had a higher penetration. The mean percent particle penetration for each lot of respirators tested 

is shown in Figure 8.

• Additionally, the respirator shown in Figure 4 that had a visual inspection concern had a value of 3.10% 

maximum penetration when tested and, therefore, was not the stockpiled respirator associated with the 

highest penetration.

Figure 8: 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.
12

CASE Findings

Findings for the KC 46727 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 [KC 2018]. Thus, these respirators tested are past their recommended shelf life. These findings 

pertain to KC units from Facility Three and may not be applicable to other stockpile facilities and/or under 

different environmental storage conditions.

Findings for the 3M 1860 Model:

No failures for inhalation resistance or exhalation resistance were observed; two failures for filtration 

performance were observed, where these two respirators came from two different lots. This model currently 

has a five-year recommended shelf life; the Appendix 2 shows a 3M letter to end users with shelf life and 

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

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

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

Stockpile Storage Conditions:

No temperature data points deviated from recommended storage conditions for the 3M model, but did for the 

KC model. %RH data points deviated from both 3M and KC’s recommended storage conditions as recorded by 

both data loggers (representing historical and current climate conditions for the respirators). Stored under these 

conditions, NIOSH found that 256 of the 258 N95 FFRs evaluated in this study, which were 8-11 years old, 

maintained their inhalation and exhalation resistance and filtration performance (i.e. 99% of tested respirators 

from Facility Three were below the NIOSH maximum limit as defined by 42 CFR Part 84).

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 holder8 (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 

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

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.
14

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. 
15

Suggested Citation 

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

Respirators: Facility Three 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 P2020-0103. 

References 

3M [2017]. Frequently Asked Questions: 3M Filtering Facepiece/Disposable Respirator Storage Conditions and Shelf Life. 

St. Paul, MN. https://multimedia.3m.com/mws/media/1015853O/faq-3m-filtering-facepiece-disposable-respirator-storageconditions-and-shelf-life.pdf [accessed February 27, 2020]. 

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 

ASTHO [2013]. Federal Emergency Preparedness Directives and Systems- Emergency Authority and Immunity Toolkit. 

Arlington, VA: Association of State and Territorial Health Officials. http://www.astho.org/Programs/Preparedness/PublicHealth-Emergency-Law/Emergency-Authority-and-Immunity-Toolkit/Federal-Emergency-Preparedness-Directives-andSystems-Fact-Sheet/.

Carias C, Rainisch G, Shankar M, Adhikari BB, Swerdlow DL, Bower WA, Piliai SK, Meltzer MI, Koonin LM [2015]. Potential 

demand for respirators and surgical masks during a hypothetical influenza pandemic in the United States. Clinical 

Infectious Diseases 60 (1): S42-S51 https://doi.org/10.1093/cid/civ141.

DHHS [2012]. An HHS retrospective on the 2009 H1N1 influenza pandemic to advance all hazards preparedness. 

Washington D.C: U.S. Department of Health and Human Services, https://www.phe.gov/Preparedness/mcm/h1n1-

retrospective/Documents/h1n1-retrospective.pdf. 

KC [2018]. Kimberly Clark Letter to Customers (Appendix 1). 

KC [2020]. Kimberly Clark representatives, email correspondence, February 25, 2020. 

NIOSH [1997]. 42 CFR Part 84 respiratory protective devices. Cincinnati, OH: U.S. Department of Health and Human 

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

https://www.cdc.gov/niosh/npptl/topics/respirators/pt84abs2.html.

NIOSH [2017]. Workplace safety and health topics: healthcare workers. Cincinnati, OH: U.S. Department of Health and 

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

https://www.cdc.gov/niosh/topics/healthcare/default.html. 

NIOSH [2018]. Standard respirator testing procedures. Cincinnati, OH: U.S. Department of Health and Human Services, 

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

https://www.cdc.gov/niosh/npptl/stps/apresp.html.

NIOSH [2019]. NIOSH conformity assessment notice: NIOSH CA 2019-1012, NIOSH respirator approval contents and 

meaning. Pittsburgh, PA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 

National Institute for Occupational Safety and Health, 

https://www.cdc.gov/niosh/npptl/resources/pressrel/letters/conformitynotice/CA-2019-1012.html.

Patel A, D'Alessandro M, Ireland KJ, Burel WG, Wencil EB, Rasmussen SA [2017]. Personal protective equipment supply 

chain: lessons learned from recent public health emergency responses. Health Security. 15 (3): 244-252 

https://doi.org/10.1089/hs.2016.0129. 
16

Rottach DR, Lei Z [2017] Stockpiled N95 filtering facepiece respirator polyisoprene strap performance. J Int Soc Respir Prot.

34 (2): 69-80 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6198819/.
17

Appendix 1 [KC 2018]
18

Appendix 2 [3M 2020]
19
20