2023 FDA Science Forum
Accelerated Aging Test Method for Estimating Expiration Dates of Surgical N95 Respirator Straps
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Contributing OfficeCenter for Devices and Radiological Health
Abstract
Personal protective equipment (PPE) in the SNS, like surgical N95® respirators, is integral to public health and safety. The long-term storage of surgical N95® respirators may adversely affect their safety and integrity. Of note, polyisoprene-based elastic straps of these respirators are reported to undergo degradation and failure before the polypropylene-based filtration components. The degradation of the straps adversely impacts the fit factor and performance of the surgical N95® respirators. However, there are no standardized test methods for assessing the durability of the elastic straps and estimating their functional lifetime. This effort aims to produce an ASTM Standard Practice and/or Regulatory Science Tool (RST) which will describe an accelerated aging test method for estimating the real time shelf-life of surgical N95 respirator straps. A feasibility study was designed to assess the degradation rate of surgical N95® respirator straps at accelerated conditions. Two groups of samples were subjected to accelerated aging at elevated temperature of 70°C and in a reaction vessel with 5 bar pressure of oxygen at 70°C for 8 weeks and 4 weeks, respectively. Dynamic Mechanical Analysis (DMA) and Attenuated Total Reflection Infrared Spectroscopy (AT-IR) were used to evaluate the mechanical performance and assess oxidative degradation of the respirator straps. The feasibility study indicated that aging in pressurized vessel leads to higher oxidative degradation and reduction in mechanical performance than aging with thermal treatment alone. Future work includes optimizing the accelerated aging test parameters and testing of surgical N95® respirator straps from various manufacturers. To develop a correlation between the degradation rates of the accelerated aged respirators and real time aged (1-10 years) respirators obtained from the SNS, the mechanical and chemical analysis results will be compared first. Secondly, a statistical model based on the Arrhenius relationship will be used to calculate the aging factor to estimate the functional lifetime of the surgical N95® respirator straps. The outcome of this study will be beneficial to manufacturers and CDRH reviewers in assessing safety and effectiveness of surgical N95® respirators and may also help with the curation of SNS.
