Integration of FDA and NIOSH Processes Used to Evaluate Respiratory Protective Devices for Health Care Workers Proceedings of a Workshop (2017) / Chapter Skim
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3 Exploring the State of the Science and Potential Priorities for Research and Standards Development
3 Exploring the State of the Science and Potential Priorities for Research and Standards Development
Pages 17-34
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From page 17... ...
TESTING THE FILTER PENETRATION PERFORMANCE OF RESPIRATORY PROTECTION DEVICES Robert Eninger, Air Force Institute of Technology Numerous factors influence filtration efficiency (see Box 3-1) , and as a result, a filter's measured filtration efficiency will depend on the test aerosol, the particle size, the way in which aerosol is measured inside and outside of the filter, and other test parameters.
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From page 18... ...
• Sensitivity and accuracy • Response (linear, logarithmic) • Calibration • Filtration efficiency metric Respirator Filter Characteristics • Substrate • Surface area • Thickness • Fiber diameter • Surface density • Electrical properties Respirator Test Conditions • Temperature • Relative humidity • Airflow • Filter pre-conditioning • Aerosol loading • Duration • Repetitions • Methods of mounting/sealing SOURCE: Presented by Robert Eninger, August 1, 2016 (Eninger, 2008)
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From page 19... ...
Starting with particle size, he explained that the NIOSH certification uses sodium chloride particles with a mean particle size corresponding to the most penetrating particle size based on the principles of mechanical filtration. The electrical charge characteristics of an aerosol can significantly influence its ability to be filtered depending on the specific filtering medium.
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From page 20... ...
Another ASTM test method listed in the FDA notice for N95 respirators, ASTM F2101, assesses biological filtration efficiency. This test changes two parameters from the ASTM particle filtration efficiency test: using aerosolized Staphylococcus aureus particles with mean diameter of approximately 3 microns and collecting the particles that pass through the filtration medium on a six-stage aerosol impactor.
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From page 21... ...
Over the past several decades, said Grinshpun, "industry has done a wonderful job improving the physical collection efficiency of filters, but faceseal leakage has been largely ignored or overlooked in designing new respirators or considering new configurations of facepieces." To measure faceseal leakage, the respirator undergoes performance testing while fitted on a human subject. Measuring particle concentration inside and outside of the respirator on the user allows the determination of what is termed "total inward leakage" -- the sum of the two types of particle penetration (through the filter and through the faceseal)
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From page 22... ...
FLUID RESISTANCE TESTING Brandon Williams, Nelson Laboratories Testing of respirators to meet the FDA criteria for fluid resistance is usually done using the ASTM F1862 test method standard, which assesses whether the synthetic blood penetrates into the layers of the respirator. The test involves dispensing synthetic blood using a pressurized cannula for a distance of 12 inches through a small hole in a target plate to which the respirator is attached.
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From page 23... ...
In Williams's opinion, blood penetration testing is important for surgical respirators because filtration materials have to be porous so the user can breathe, but porous products will allow for some liquid penetration. He noted that they are not aware of any other test result that could be used as an indicator for how the product will perform in the blood penetration test.
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From page 24... ...
FLAMMABILITY TESTING FOR RESPIRATORS Samy Rengasamy, National Personal Protective Technology Laboratory At first glance, fire hazards would not seem to be a risk to which health care workers are exposed, but in fact, said Rengasamy, when surgical fires do happen, they can be catastrophic. He noted that the Emergency Care Research Institute reports that about 600 surgical fires occur in the United States each year.
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From page 25... ...
The takehome messages, he said, are that NIOSH has the capacity to perform the 16 CFR 1610 flammability testing and that there may be several N95 1 16 CFR 1610 states that plain surface textile fabrics that have a burn time of 3.5 seconds or more are classified as Class 1, normal flammability; for raised surface textile fabrics, Class 1 is used for those with a burn time of more than 7 seconds. For raised surface textile fabrics, intermediate flammability (Class 2)
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From page 26... ...
Having spent much of his academic career developing test methods to look at thermal protection for protective clothing, Barker said one thing he knows to be true is that there are many variables, such as the ignition source and oxygen level, that can affect and determine flammability beyond the material itself. He also pointed out that all of the recognized test methods look solely at the filtration material, not the entire respirator.
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From page 27... ...
Based on their intended clinical use and the FDA 2004 guidance document for surgical masks (FDA, 2004) , surgical N95 respirators are classified as surface devices that contact intact skin for a limited duration.
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If so, the sponsor will need to justify the switch and include a certification stating that the test article is identical to the proposed medical device in its final finished form in formulation, BOX 3-2 FDA-Recognized Consensus Standards for Biocompatibility Testing • In vitro cytotoxicity testing: ISO 10993-5:2009/(R) 2014 Bio logical evaluation of medical devices -- Part 5: Tests for in vitro cytotoxicity.
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From page 29... ...
If this cleared respirator has established a history of safe use in the intended application and user population, the sponsor may provide a material certification statement for comparison to the previously cleared device in lieu of new biocompatibility testing. FDA may have additional concerns about biocompatibility, Qian noted, if a surgical N95 respirator has additional specific issues, including having materials known to be associated with significant health problems, having antimicrobial or other specific coatings, if it is intended to be used in biologically vulnerable populations, or if it contains special labeling claims.
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From page 30... ...
FDA confirms that the respirator has a valid NIOSH certification number and therefore has met the particle filtration efficiency standards and the other NIOSH requirements. Then FDA looks at whether the product also meets the biocompatibility, flammability, and fluid resistance standards and, if so, the product could be approved as a surgical N95 respirator.
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From page 31... ...
Jeffrey Peterson from NIOSH's NPPTL explained that when NIOSH receives products that have an antimicrobial or infection control claim, they talk with the manufacturer and coordinate with FDA to ensure that the product is undergoing the appropriate tests to meet the FDA criteria. Fluid Resistance Testing James Chang noted that blood and body fluid splash is a significant challenge in protecting health care workers.
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From page 32... ...
James Johnson said Zeigler's comment points to the need for research on how these respirators are used in practice in operating suites and other areas of the hospital. Flammability Testing In clarifying the need for flammability testing of N95s for use in health care settings, Cohen mentioned that the specific occupational hazards need to be more carefully assessed.
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From page 33... ...
Cohen, commenting on the importance of biocompatibility and flammability testing, agreed with Rose and said, "it appears to me that these are two issues that could be well handled by the manufacturer by saying these are standards that you must meet, which is really what FDA does." If there is an issue, he said, FDA or NIOSH would investigate as opposed to adding a requirement for biocompatibility and flammability testing to the NIOSH certification test.
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From page 34... ...
Joyce Lee, a toxicologist at Halyard Health, agreed that examining irritation and sensitization are important both for the patient and the clinician. Overarching Comments Andrew Levinson from OSHA noted that the protective value of an unworn respirator is zero and that this is "really the first time that NIOSH is looking at an industry-specific respirator standard that would be just for health care usage." Given that, he wondered if there was a need to have standards for user acceptability criteria such as heat and moisture buildup and breathing resistance that would strike a balance between adequately protecting people but not overly protecting them with a respirator that is uncomfortable and less likely to be worn.
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