用蒸汽灭菌对N95面膜进行去污染

Written by:Amit Gupta

Can N95 Masks be steam sterilized for reuse? This article attempts to answer this question by giving a review of the current literature and taking a closer look at N95 filter types and materials of construction.

高压釜N95口罩将理想的能力because autoclaving is a proven sterilization process and existing autoclave infrastructure is ubiquitous in labs, hospitals, dental offices, and many other types of facilities. While data from studies performed in years past suggested that steam autoclaves were ineffective for the reprocessing of used N95 masks, newer data suggests that the earlier studies did not necessarily paint the whole picture, and in instances where technologies like Hydrogen Peroxide vapor and UV-C are not available, supplies of N95 respirators may be stretched through the use of autoclave decontamination.

Background

进入冠状病毒大流行，人们普遍关注个人防护设备（PPE） - 特别是N95口罩。在过去的几个月中，已经进行了许多研究，以净化N95面膜，以使其安全地重复使用。正如我们在我们的previous post，过氧化氢蒸气和UV-C光净化是N95去污的流行方法。不幸的是，在美国和世界各地的许多地区，这些技术要么不可用，要么太昂贵或太复杂而无法实施。

N95 Filter Type – Electrostatic vs. Pleated

N95掩码通常采用两种不同的过滤技术之一。N95蒙版的第一类使用熔体的聚合物纤维，该聚合物纤维充满了静电电荷，该过滤层称为element。当颗粒通过该带电荷的过滤器时，它们被电磁场捕获。这些类型的口罩也称为杯面具。

第二类N95使用类似于HEPA过滤器的打褶纤维过滤器。百褶过滤器依赖于纤维的紧密填充密度来机械防止颗粒的通过 - 类似于屏幕的工作方式，但在显微镜下。这些类型的面具也称为扁平褶皱或折叠面具。

静电N95面膜彼得·泰（Peter Tsai）共同发明的数据表明，蒸汽和冷凝水可能对element影响不大。在“绩效和防止Covid-19及其通过灭菌以重复使用面罩的效率降解”（4）TSAI发现，N95口罩中使用的element过滤元件上的电荷在典型灭菌温度下暴露于Steam后没有明显的损失250⁰F（121⁰C）持续3分钟。但是，得克萨斯州医学院（11）收集的数据发现，Prevacuum高压灭菌器中的一个完整的30-60分钟蒸汽去污染周期降低了3M 1860（带有element）的过滤效率，至95％以下。

Pleated style filters don’t have an electret. Studies on pleated style N95 masks were published by Anand Kumar et. al (4). Kumar analyzed the impact of steam decontamination in a laboratory autoclave analogous to a Consolidated model 3AV-X1. The cycle was set to a sterilization temperature of 250⁰F (121⁰C) with a sterilization time of 15 minutes. All four models of masks used (3M 1860, 3M 1870, 3M VFlex 1805 and AO Safety 1054S) were able to withstand autoclave treatment at these parameters and successfully pass quantitative fit tests. Kumar showed that the three pleated filter N95 masks could withstand at least 10 autoclave sterilization cycles before failing fit tests and the popular 3M 1860, which uses an electrostatic filter, was only able to withstand one autoclave cycle before showing unacceptable degradation.

A Texas study by Nathan Bopp et al. (11) found that 3M models 1805 and 1870 could pass fit testing after 3 autoclave cycles. The degradation of filter integrity was tested after 3 cycles at 250⁰F (121⁰C) for 30m and 239⁰F (115⁰C) for 60m. Results indicated that the lower-temperature 60 minute decontamination cycle degraded filtration integrity less than the higher-temperature shorter cycle. However, all masks showed filtration efficiency dropped below 95% even after 1 cycle of processing.

Mask Construction – Materials and Glues

较早的研究（8）表明，参与典型的蒸汽灭菌周期的250⁰F（121⁰C）的高温变形了某些掩模模型的材料。不幸的是，这项研究并未列出使用了哪种模型N95，并且许多人将此结果解释为同样适用于所有N95蒙版的模型。此外，另一项研究（1）表明，在273⁰F的更高温度（134°C，未报告时间）下，蒸汽灭菌会损坏3M 8822型面膜。

Studies performed by de Man (9) and van Statren (10) showed that the 3M 1862+ N95 mask was able to withstand standard steam sterilization cycles at temperatures of 250⁰F (121⁰C) for 15 minutes for up to five cycles prior to unacceptable loss of filtration efficiency. Additionally, these masks passed pressure drop and fit testing based on the author’s standards. They also showed that while processing masks at 250⁰F (121⁰C) was successful, processing at 273⁰F (134⁰C) was not. The 3M 1862+ mask used in these experiments has an electrostatic filter element.

As of May 2020, the 3M corporation still does not recommend the use of high temperature, autoclaving or steam heat to disinfect 3M N95 masks (2). However, 3M’s latest technical bulletin outlines parameters employing temperatures between 60-70C and 50-80% relative humidity for 30 minutes to decontaminate certain models of N95 masks. It is important to note that this temperature range may not inactivate all organisms. Organisms that are more difficult to inactivate like fungus and bacterial spores may survive. As such, the mask may not be sterile but rather have a reduced population of contaminating organisms.

3M model 1870 N95 Respirator (Pleated Fabric Design)

3M 1860 N95呼吸器（刚性设计）

SARS-COV-2病毒灭活

Kumar’s study also included tests on viral inactivation of SARS-CoV-2, the virus that causes COVID-19. Kumar inoculated masks prior to autoclaving and compared viral growth with unprocessed control masks. On all four models of mask, sterilization by autoclaving resulted in a total inactivation up to detection limits of SARS-CoV-2 viral particles. It is worth noting that while the masks were only inoculated with 5.0 Log TCID50 of SARS-CoV-2 so a 6 Log reduction was impossible to show. However, after processing, no virus was recovered.

Conclusion

Experiments performed on various methods of decontamination on N95 masks have shown a great need to validate the method on the specific mask to be used. Even popular methods like hydrogen peroxide vapor cannot be used on masks that contain cellulose. Similarly, the use of high temperature steam for autoclaving N95s cannot be categorically accepted nor rejected.

虽然初始结果似乎可以更好地重复使用打褶/折叠的样式面具，但一些测试表明过滤效率的丧失（11）。关于静电/杯子风格的口罩，还进行了一些成功和一些不成功的测试。就N95掩模拟合和过滤性能而言，最可重复的潮湿热数据指向在相对湿度升高时使用低于100c的温度。最佳实践将建议在确定蒸汽灭菌是否合适之前使用特定的品牌和N95蒙版进行高压釜测试。

For reference, here are some commonly available models of N95 masks with references to studies that tested them.

参考：

1)https://www.rivm.nl/en/documenten/reuse-of-ffp2-masks

2)https://multimedia.3m.com/mws/media/1824869O/decontamination-methods-for-3m-n95-respirators-technical-bulletin.pdf

3)https://www.medrxiv.org/content/10.1101/2020.04.05.20049346v1

4)https://utrf.tennessee.edu/information-faqs-performance-protection-sterilization-of-face-mask-materials/

5) Fisher, E.M., J.L. Williams, and R.E. Shaffer,Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.PLoS One, 2011.

6）https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html

7）https://www.nebraskamed.com/covid

8) Viscusi DJ,国王WP,沙福尔再保险。Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models. J Int Soc Respir Prot. 2007;24:93–107.

9)http://resolver.tudelft.nl/uuid:f048c853-7e1d-4715-b73d-b73d-3b506b274a30

10）http://resolver.tudelft.nl/uuid:078a3733-84d6-4d4a-81e6-74210c7fed78

11）BOPP，Nathen＆Bouyer，Donald＆Gibbs，Christopher＆Nichols，Joan＆Ntiforo，Corrie＆Grimaldo，Miguel。（2020）。N95过滤面部呼吸器的多环形高压抗解。应用的生物安全。153567602092417. 10.1177/1535676020924171。

12)https://www.medrxiv.org/content/10.1101/2020.04.01.20050443v2

免责声明：认识到COVID-19危机，合并的灭菌器系统仅共享从公共资源提供的信息。库博体育是真的吗CSS对此处共享的信息没有任何形式的陈述或任何形式，明示或暗示的明示或暗示。CSS尚未科学评估特定方法或技术去污染PPE或FFP材料。决定使用任何方法用于应用PPE或FFR去污染的决定只能由合格的医务人员自行决定。此处包含的信息不代表医疗建议，也不代替监管指导和/或要求。使用此信息是您的唯一风险。

Amit Gupta

Amit has over 15 years of experience engineering multi-disciplinary systems and brings his passion for engineering, innovation and quality to his work every day. Prior to joining Consolidated Sterilizer Systems in 2007, Amit worked on robotics at the Charles Stark Draper Laboratories. Additionally, he designed medical devices and scientific equipment such as novel catheters and DNA hybridization chambers for microarrays. A true engineer at heart, Amit enjoys breaking things just to figure out how to fix them; his love of tinkering even extends to assembling IKEA furniture. He graduated from the University of Pennsylvania with a B.S. in Mechanical Engineering and from MIT with an M.S. in Mechanical Engineering.

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