PPE CASE

Personal Protective Equipment Conformity Assessment Studies and Evaluations

Testing of Stockpiled ANSI/AAMI PB70 Level 4 Surgical Gowns

To instill confidence in workers that personal protective equipment (PPE) will be protective, leaders in the PPE 

community develop performance standards and then check to see if the PPE meets these standards (i.e., 

conforms). This process includes a variety of public and private sector entities depending on their expertise 

involving the particular PPE and hazards. To bring greater oversight and coordination to these activities, the 

National Institute for Occupational Safety and Health (NIOSH) developed the

National Framework for Personal Protective Equipment – A Conformity Assessment 

Infrastructure.

The Framework assists leaders of the PPE community in developing activities that 

are appropriate given the risk posed to the worker. NIOSH works with public and 

private sector entities to assess and improve upon conformity assessment activities

by collecting PPE from the marketplace or at the point of use. NIOSH then 

evaluates the PPE against established standards and uses the test results to provide 

leaders in the PPE community guidance on post-market sampling strategies, 

evidence-based criteria for PPE acceptance or rejection, and potential performance 

requirement updates. 

This report relates to work conducted at the request of the Centers for Disease 

Control and Prevention (CDC) Strategic National Stockpile (SNS). The SNS asked 

NIOSH to evaluate a specific surgical gown model that was in the process of being 

purchased for the SNS to determine if that gown model met CDC 

recommendations for use while providing care to patients with Ebola. Specifically, whether this gown model 

passed the Level 4 requirements of American National Standards Institute (ANSI)/Association for the 

Advancement of Medical Instrumentation (AAMI) PB70:2012, “Liquid Barrier Performance and Classification 

of Protective Apparel and Drapes Intended for Use in Health Care Facilities.” 

Keywords: PPE, surgical gowns, stockpile, ASTM, ANSI/AAMI PB70

Abbreviations: 

ANSI/AAMI: American National Standards Institute/Association for the Advancement of Medical Instrumentation

ASTM: American Society for Testing Materials

AATCC: American Association of Textile Chemists and Colorists

ASQ: American Society for Quality

SNS: Strategic National Stockpile

RQL: Rejectable Quality Level

NIOSH determined that 

existing surgical gown 

test methods require 

greater clarification to 

ensure consistent 

evaluations and 

conclusions. 

Additionally, NIOSH 

recommends that a 

post-market conformity 

standard be developed. 
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What NIOSH Did to Protect the Worker

• NIOSH evaluated one model of a Level 4 surgical gown from a single manufacturer at the request of the 

SNS to determine if the gown model met the appropriate performance standards. The manufacturer 

indicated the gowns meet ANSI/AAMI Liquid barrier performance and classification of protective apparel 

and drapes intended for use in health care facilities (ANSI/AAMI PB70:2012) Level 4 requirements. The 

test methods used were those specified for ANSI/AAMI PB70 (AAMI PB70 hereafter) Level 4 testing

including ASTM F1671: Standard Test Method for Resistance of Materials Used in Protective Clothing to 

Penetration by Blood-Borne Pathogens Using Phi-X174 Bacteriophage Penetration as a Test System and 

AATCC 42: Water Resistance: Impact Penetration.

o NIOSH received two cases (30 gowns in each case and each case from a different lot

manufactured in 2014) of the gowns purchased by the SNS, but sent to NIOSH’s National 

Personal Protective Technology Laboratory (NPPTL) to conduct the evaluation. Several months 

after receiving the gowns for the SNS, NIOSH NPPTL acquired two additional cases of gowns 

from the open market to be used as control gowns. Manufactured in 2015, these gowns had 

visibly different seam sealing than the gowns manufactured in 2014. 

o NIOSH funded an accredited third party testing laboratory to evaluate each gown at the three 

critical zones identified by AAMI PB70 (sleeve seams, tie attachments, and chest area) using

ASTM F1671 and AATCC 42 test methods. The ASTM F1671 test methodology provides 

procedures for testing material both using a supporting screen and without a screen. The third 

party testing lab performed both variations. 

• The AAMI PB70 standard requires manufacturers to implement a quality system that rejects lots with a 

failure rate greater than or equal to 20% at least 90% of the time. This is known as the rejectable quality 

level (RQL). NIOSH NPPTL created a red/yellow/green stoplight analogy based on the RQL and levels of 

concern. Green is for instances where the failure rate of testing is below the RQL. Yellow is for 

intermediate failure rates, where more testing would likely be needed. Red is where failure rates are

significantly higher than the RQL and indicates the gowns may not provide the expected level of 

protection. 

For an evaluation of 32 gowns, NIOSH NPPTL considered 0-6 failures as green, 7-9 failures as yellow, and 10 or 

more failures as red.

Table 1. Red/Yellow/Green Criteria for Sets of 32 Samples at 20% RQL
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What NIOSH Found Through Testing and Evaluation

• AATCC 42: Water Resistance Test Method 

o NIOSH NPPTL tested 32 gowns (16 from each gown lot manufactured in 2014) at the noncritical 

zones on the front (i.e., outside of the critical zones). All of the 2014-manufactured gown 

samples tested met AAMI PB70 AATCC 42 testing criteria. 

• ASTM F1671 Test Method 

o Without screen test methodology (Table 2, Procedure A)—For the surgical gowns received from 

the SNS (ASTM F1671 testing of 32 samples from sleeve seams, 32 samples from chests, and 32 

from tie attachments), the results yielded four failures on the sleeve seams —three failures from 

one lot and one failure from the second lot. With four failures found out of the 32 tested 

samples, NIOSH NPPTL considered this a green result. On the control samples, the third party

testing lab only tested ASTM F1671 at the sleeve seam. One control sample failed out of 32 on 

the sleeve seams with the ASTM F1671 test method. 

o With screen test methodology (Table 2, Procedure B)—The manufacturer provided a custommade flat, stainless steel screen that meets the ASTM F1671 requirements. NIOSH used the

same gown sleeves at different locations for ASTM F1671 Procedure B testing and the results 

yielded two failures on one lot from the 2014-manufactured samples and one failure on the 

control samples. None of the failures occurred on the gowns that failed the testing without the 

screen. The ASTM F1671 method specifies the use of a screen when testing elastomeric or 

extensible materials if any distortion of the test material is suspected of causing a failure; 

however, testing without a screen is expected to give worst-case scenario. With only two out of 

32 gown samples failing the ASTM F1671 test, NIOSH NPPTL considered this a green result. 

Table 2. ASTM F1671 Test Results

Year of 

Manufacture Lot Critical 

Zone

Quantity 

Tested

Procedure A 

(No Screen) 

Failures

Procedure B

(With Screen) 

Failures

Procedure A & B 

Failures on same 

sleeve

2014 A - SNS Sleeve 16 3 0 0

2014 B - SNS Sleeve 16 1 2 0

2015 C - Open 

Market Sleeve 32 1 1 0

2014 A - SNS Tie 16 0 Not Tested Not Tested

2014 B - SNS Tie 16 0 Not Tested Not Tested

2014 A - SNS Chest 16 0 Not Tested Not Tested

2014 B - SNS Chest 16 0 Not Tested Not Tested
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CASE Conclusion

NIOSH NPPTL evaluated one model of SNS stockpiled Level 4 surgical gowns according to the requirements of 

AAMI PB70 liquid barrier classification standard for verification of adequate barrier performance in specified 

regions of the gown. Tests included ASTM F1671 (Viral Penetration Resistance) and AATCC 42 (Water Resistance: 

Impact Penetration). For ASTM F1671, results were inconsistent both when testing with the stainless steel 

screen (which reportedly masks up to 42% of the material surface) and testing done without the screen. All 

testing results showed failure rates under the RQL, thus NIOSH NPPTL gave green results for all sets of testing. 

However, this evaluation was limited to gowns selected from two lots. Therefore, the conclusions cannot be 

generalized to state that the majority of the gowns provided by the SNS were consistent with the CDC 

recommendations for use while providing care to patients with Ebola. In addition, the findings were limited to 

the samples received as there was no attempt at random sampling to select gowns for testing. NIOSH NPPTL 

concludes that there is not sufficient evidence to challenge the manufacturer’s claim of the gowns 

manufactured in 2014 being compliant with the requirements of Level 4 of the AAMI PB70 standard.

Actions the PPE Community May Take to Further Protect Workers

• The ASTM F1671 test method does not provide objective criteria for use of the supporting screen, nor 

does it provide sufficient detail to construct consistently similar screens. The design and specifications of 

the screen should be clarified in order to receive consistent test results from labs. 

• AAMI PB70 was the only conformity-related classification standard that could be identified for surgical

gowns in the United States. However, this standard is designed for pre-market conformity 

considerations. While the AAMI PB70 standard is not sufficient to identify pass or fail criteria for third 

party post-market product audits, it may provide a foundation for such a standard. For use as a postmarket standard, NIOSH makes the following recommendations:

o PPE Community: Request that the manufacturing process for surgical gowns meet existing 

quality standards.

o Standards Development Body: (1) Require full implementation of a standards compliant 

sampling plan, such the ASQ Z1.9 and Military (MIL)-STD-1916 currently mentioned in the AAMI 

PB70, to determine sampling plans and (2) develop a consensus-based standard for post-market 

conformity verification—i.e., for products on the market and being used by workers—taking into 

account time in storage and other factors likely to affect protection.

Actions the PPE Users, Selectors, and Purchasers May Take to 

Further Protect Themselves and Others from Hazards

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

notifications relevant to PPE.
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For more information related to personal protective equipment, visit the NPPTL website

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

To receive documents or other information about occupational safety and health topics, contact NIOSH:

Telephone: 1–800–CDC–INFO (1–800–232–4636)

TTY: 1–888–232–6348

CDC INFO: https://www.cdc.gov/cdc-info/

or visit the NIOSH website at https://www.cdc.gov/niosh/

For a monthly update on news at NIOSH, subscribe to NIOSH eNews by visiting 

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

Disclaimer 

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. 

Suggested Citation

NIOSH [2017]. PPE CASE: testing of stockpiled ANSI/AAMI PB70 level 4 surgical 

gowns. By Rottach D, Fries M, Kilinc-Balci FS, Moore S, Shaffer R. 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 P2017-0102.