A Hack for Sterilizing N95 Respirators
N95 respirators were intended to be discarded after every use. That’s not happening now, of course, so much research is going into devising methods for sterilizing used respirators for reuse. If that is your situation, the following information may be helpful:
Bleach, isopropyl alcohol and hydrogen peroxide all kill viruses—but also destroy the fabric integrity. Autoclaves can also kill viruses, but most assembly plants don’t have spare autoclaves. However, some valuable work has been published recently about a simple, inexpensive way to repeatedly sterilize N95 respirators using a simple inexpensive rice cooker. The first published study was conducted with Farberware rice cookers (Model No. WM-CS6004W), but the Instant Pot rice cooker has been used in other studies. (Very important: Do not reuse the cooker for food.)
Heating respirators for 50 minutes at 212 F—the default setting on most rice cookers—effectively resulted in sterilization. Respirators, including straps, can tolerate that temperature pretty well, but it’s necessary to line the cooker with paper to form a barrier between the respirator and the based and walls of the cooker.
More recent research indicates that moist heat at the same temperature works better and faster. If you’d like to investigate, there’s a very technical NIH online paper here or a simplified explanation here. The Department of Homeland Security site offers some PDFs about selecting and using a rice cooker for decontamination.
Do not rotate respirators among people. Once a respirator has been used by a person, it must be used solely by that person even after sterilization. Put identifying markings (that can tolerate sterilization conditions) on every respirator.
This virus is much worse than initially believed. People of all ages really do die, and there’s considerable evidence that organs (lungs, of course, but also hearts and kidneys) often suffer serious lasting damage even in young, previously healthy people without outward symptoms. A revolting new, uniquely American, development is the possibility that COVID-19 survivors may fall into the “pre-existing condition” category for health insurance at a time when the Supreme Court is about to consider whether to kill the Affordable Care Act (and, thus, insurance coverage protection for pre-existing conditions). So please be careful and stay well.
Editor’s note: Jim Smith began work in electronics assembly in 1965 and founded Electronics Manufacturing Sciences in 1981 to teach soldering as a unified science. Thousands of engineers, technicians and managers worldwide have attended his "Science of Soldering" classes. Jim’s articles have appeared in more than 100 publications worldwide. His "Unconventional Wisdom" column appeared monthly in ASSEMBLY Magazine for more than 10 years and he remains a regular contributor to the magazine. For more information, visit www.emsciences.com.
Looking for quick answers on assembly and manufacturing topics? Try Ask ASM, our new smart AI search tool. Ask ASM