PPE CASE

Personal Protective Equipment Conformity Assessment Studies and Evaluations

Performance of Stockpiled Air-Purifying Respirators, Facility Four

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

[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 air-purifying respirators. 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 

respirators and P95 filters collected from Facility Four of Ten. This facility is a state stockpile facility.

NIOSH found that 540 of 574 

N95 filtering facepiece 

respirators and P95 filters

stockpiled at Facility Four that 

were 8-12 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 Four

• NIOSH researchers visited Facility Four in March 2018 (Figure 1). This facility was located within the U.S. 

Department of Health and Human Services Region 9, representing Arizona, California, Hawaii and 

Nevada.

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 Four 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. This data was collected in 60-minute intervals from October 2017 to November

2018.
3

Collection of Respirator Samples

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

well as one P95 filter cartridge model. Samples were collected from six different manufacturing models1

: 

1) 3M 1860 (two different manufacturing years); 2) 3M 1870; 3) 3M 8210; 4) 3M 9010; 5) 3M 2071; and 

6) Kimberly Clark (KC) 46827 (Table 1). 

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

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

were sampled to evaluate and attempt to account for inter-lot variation. More than two lots were 

sampled from a model if conditions presented “worst-case scenario” conditions within the facility.

Products were sampled and shipped to the NIOSH facility overnight to reduce exposure to non-climatecontrolled 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 Four. 

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].
4

Table 1. APRs Sampled from Stockpile Facility Four

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 12 years Past 5-year shelf 

life 4

3M 1860 Lot A 2010 No

8 years

Past 5-year shelf 

life4 3M 1860 Lot B 2010 No

3M 1870 Lot A 2010 No

8 years

Past 5-year shelf 

life4 3M 1870 Lot B 2010 No

3M 8210 Lot A 2006 No

12 years

Past 5-year shelf 

life4 3M 8210 Lot B 2006 No

3M 9010 Lot A 2006 No

12 years

Past 5-year shelf 

life4 3M 9010 Lot B 2006 No

3M 2071 Lot A 2006 No

12 years

Past 5-year shelf 

life4 3M 2071 Lot B 2006 No

KC 46827 Lot A 2007 No

11 years Past 5-year shelf 

life5 KC 46827 Lot B 2007 No

KC 46827 Lot C 2007 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 3M 1860 and 3M 2071 controls were manufactured in 2018, the 3M 8210 

controls were manufactured in 2015, the 3M 1870 controls were manufactured in 2014, the 3M 

9010 controls were purchased in 2018 but have an unknown manufacturing date, and the KC 46827 

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.

3 Testing was completed in 2018. 4 3M designated a five-year shelf life for these models [3M 2018]. As of February 2020, these models still have a five-year 

shelf life.

5 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.
5

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 53: Liquid Particulate Filter 

Efficiency for P95

<5.0% particulate penetration 

(>95.0% filter efficiency) 407 20

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 Four; 

examples of the most amount of dust and damage to product packaging are shown in Figures 2, 3, and 

4. Nine boxes shown minor damage. Of the 574 respirators visually inspected, no concerns were noted.

Figure 2: Most amount of dust observed on product cases from Facility Four.

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.
6

Figure 3: Most amount of product case damage observed from Facility Four. 

Figure 4: Most amount of product box damage observed from Facility Four.

• Facility lights were off when not in use. Small ceiling vents allowed sunlight to enter the facility in 

specific locations on the top pallet. 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 but not across the top or bottom. With the exception of the top-most row, pallets were 

stacked two-high causing some weight/load to be applied to the bottom pallet. 

• 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, 3M 1870, 3M 8210, 3M 9010, and 3M 2071: 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]

o Data was aggregated across the two data loggers. The average temperature between the 2017-

2018 time period was 67.0°F. The average %RH between 2017-2018 was 49.6%; the average

temperature is within the 3M recommended temperature but deviates for the KC 

recommended temperature. The average %RH meets both 3M and KC’s recommended %RH 

storage conditions.

o For the 3M models, 0.02% of the total temperature data points deviated from the 

recommended storage conditions. For the KC 46827 model, 62.0% of data points were below 
7

68°F and 4.4% were above 77°F. For %RH, no data points deviated from 3M’s recommended 

storage conditions, and 25.8% of data points deviated from KC’s recommended conditions.
8

Figure 5: Percent Relative Humidity (% RH) from October 2017 – November 2018 for two data loggers stored at 

Facility Four. Data is plotted as a 50-point moving average for visualization purposes. Maximum and minimum 

temperatures reported are noted for each data logger.
9

Figure 6: Temperatures from October 2017 – November 2018 for two data loggers stored at Facility Four. Data is 

plotted as a 50-point moving average for visualization purposes. Maximum and minimum temperatures 

reported are noted for each data logger.
10

Inhalation and Exhalation Resistance

• NIOSH evaluated the inhalation and exhalation resistance for a total of 39 stockpiled and 18 control 

respirators. All stockpiled and control respirators from each model passed these tests. The 3M 1860, 

3M 1870, 3M 9210, and 3M 9010 data are shown in Figure 7. The 3M 2071 (P95 filter cartridge) data is 

shown in Figure 8. The KC 46827 data is shown in Figure 9.

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

α<0.05) between the controls and 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 3M 1870 stockpiled 2006 Lot B displayed significantly 

lower inhalation and exhalation resistance when compared to the control. 

• For inhalation resistance, the individual stockpiled respirator with the highest resistance (17.02 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 (14.22 mm H2O) 

was below the NIOSH maximum limit for product approval (25 mm H2O allowable maximum).
11

Figure 7: Control and stockpiled respirator inhalation (A) and exhalation (B) resistance data for the 3M 1860, 3M 

1870, 3M 8210, and 3M 9010 models. 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.
12

Figure 8: Control and stockpiled respirator inhalation (A) and exhalation (B) resistance data for the 3M 2071 

model. P95 filters 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.
13

Figure 9: Control and stockpiled respirator inhalation (A) and exhalation (B) resistance data for the KC 46827 

model. 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.
14

Filtration Performance

• NIOSH evaluated the particulate penetration efficiency for 535 stockpiled respirators and 120 controls. 

The 3M 1860, 3M 1870, 3M 9210, and 3M 9010 data are shown in Figure 10. The 3M 2071 (P95 filter) 

data is shown in Figure 11. The KC 46827 data is shown in Figure 12.

• 34 individual stockpiled respirators—all KC 46827—exceeded the 5.0% maximum. Twenty-five failing 

units came from one production lot while the remaining 9 came from a second lot, both manufactured 

in 2007. The third lot tested did not show any failures. The highest penetration for an individual KC 

46827 stockpiled respirator was 8.90% and the highest penetration for an individual KC 46827 control 

respirator was 2.84%. 

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

α<0.05) between the 3M controls and 3M stockpiled respirators for filtration when averaging across 

models. There was a statistically significant difference between the KC controls (mean percent 

penetration=1.77%, SD=0.45) and KC stockpiled respirators (mean percent penetration=4.36%, 

SD=1.44), p<0.001. 

• 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 A had a higher penetration; 2) 3M 1860 stockpiled 2010 Lot B 

had a higher penetration; 3) both 3M 1870 stockpiled 2010 Lots A and B had a higher penetration; 4) 3M 

8210 stockpiled 2006 Lot A had a lower penetration; 5) all three KC 46827 stockpiled 2007 lots had a 

higher penetration; and 6) 3M 2071 stockpiled 2006 Lot B had a higher penetration. 
15

Figure 10: Control and stockpiled respirator particle filtration performance data for the 3M 1860, 3M 1870, 3M 

8210, and 3M 9010 models. 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.
16

Figure 11: Control and stockpiled respirator particle filtration performance data for the 3M 2071 model. P95 

filters must have a liquid 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.

Figure 12: Control and stockpiled respirator particle filtration performance data for the KC 46827 model. 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.
17

CASE Findings

Findings for the KC 46827 Model:

No failures for inhalation resistance or exhalation resistance were observed; 34 failures for filtration 

performance were observed. Twenty-five failing units came from one production lot while the remaining 9 

came from a second lot, both manufactured in 2007. This model currently has a five-year 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 Four and may not be applicable to other stockpile facilities and/or under different 

environmental storage conditions.

Findings for the 3M 1860, 3M 1870, 3M 8210, 3M 9010, and 3M 2071 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 five

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 Four and may not be 

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

Stockpile Storage Conditions:

For the 3M models, 0.02% of the total temperature data points deviated from the recommended storage 

conditions. For the KC 46827 model, 62% of the temperature data points deviated from the recommended 

storage conditions. For %RH, no data points deviated from 3M’s recommended storage conditions, and 26% of 

data points deviated from KC’s recommended conditions. Stored under these conditions, NIOSH found that 540 

of the 574 APRs evaluated in this study, which were 8-12 years old, maintained their inhalation and exhalation 

resistance and filtration performance (i.e. 94% of the sampled respirators 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 

8 An approval may be granted to a non-manufacturing entity.
18

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.
19

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. 
20

Suggested Citation 

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

Respirators: Facility Four 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 P2020-0104. 

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. 
21

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/.
22

Appendix 1 [KC 2018]
23

Appendix 2 [3M 2018], [3M 2020]
24
25
26
27