How have sterilization techniques evolved?

N95 masks, which are sometimes also called N95 respirators, have probably been the most popular item among healthcare centers around the United States for protection during the pandemic. Since they can filter out a wide variety of particles, they can have multiple uses in different industries for respiratory protection. Some of these particles are dust, pollen, coal smoke, and even bioaerosols like the flu virus or the coronavirus.

Their use for antiviral protection has earned these masks the title of the best face mask for virus protection during the pandemic, which is why they’ve become an indispensable item in healthcare facilities. Before this situation began, these masks could be found for sale anywhere, whether it was a physical or an online store.

But now, when hospitals have to buy them in bulk and wholesale purchases, this demand has turned them into a scarce item in the USA. Even though other items, like surgical masks, KN95 masks, face shields, gloves, and gowns, have also been highly requested and become scarce, this mask is the most affected one by the shortages reported across the country.

This situation has led to the development and evolution of the available sterilization techniques used for medical supplies. Let’s take a look at what the Centers for Disease Control and Prevention (CDC) says currently about decontaminating respirators and other devices.

The CDC’s guidelines

Their website has some detailed information regarding the decontamination of respirators. They start by explaining that, in the case of a limitation in the supplies available in a specific center, a series of strategies can be implemented to make sure workers are still protected. When it comes to the decontamination and reuse of respirators, like the N95 masks, they’re very clear in explaining that other measures and strategies need to be considered first, which they list on their website.

However, when all of them are implemented and the scarcity is still a problem and shortages are still reported, this is the moment in which facilities need to implement the decontamination and reuse of respirators. And, although the CDC offers some guidance and general information, they’re also very clear in explaining that the methods used for decontamination need to be selected individually for each respirator model, following the instructions and information provided by the manufacturer, if available. When this isn’t the case, looking for guidance in third-party organizations would be the next best option, and both of these guidelines would supersede anything the CDC recommends.

To illustrate this, we can talk about 3M N95 masks. The company 3M has recommendations for the sterilization process used in each of their models, like the 3M 1860, the 3M 8210, and the 3M 8511. All of them were updated in April, and they supersede anything the CDC would say on their website.

About the decontamination methods used at the moment for respirators, they say that for them to be effective, they have to inactivate the target pathogen in the filter media, obviously. But, other additional properties they must show include not affecting the fit of the respirator and not damaging the filter media in the process.

Currently, only three methods have been named by both the CDC and the Food and Drug Administration (FDA) as potentially effective for respirators, which are ultraviolet germicidal irradiation, vaporous hydrogen peroxide, and moist heat. These have been used for the sterilization of medical devices for a very long time, and after being tested for respirators during the pandemic, they have shown efficacy for eradicating the SARS-CoV-2 in them.

Each of the methods used today:

  • Ultraviolet germicidal irradiation: this involves the use of ultraviolet lights on respirators due to their antiviral properties. Multiple masks can be sterilized simultaneously by placing them in a room with UV lights and making sure all parts of the respirator are exposed. Out of the three methods mentioned, this one is the fastest, decontaminating the respirators in only 15 minutes.
  • Vaporous hydrogen peroxide: a lot of healthcare facilities already have the devices that use this substance as a decontamination method, since its antimicrobial properties are well-known and have been used for many years. Around 45 minutes are necessary for the decontamination of a respirator, and 50 cycles can be applied before it starts degrading.
  • Moist heat: respirators are exposed to high humidity levels and temperatures. To sterilize respirators, however, they need to endure multiple cycles, which causes the most damage to them out of the three methods. However, it’s currently considered one of the most effective ones.

An alternative to moist heat: dry heat

Although it’s not cited by the CDC as an effective decontamination method, during the pandemic there were a lot of studies about the use of dry heat in respirators. One study in particular showed that the use of an electric cooker to apply dry heat on N95 masks could decontaminate them in 50 minutes without damaging the respirator.

To learn more about this innovation, you can read about it here.

These are all great breakthroughs to ensure healthcare workers are protected while they work. However, after using any of the methods mentioned, it’s always recommended to check the fit of the respirator and to check if there’s the degradation of any of the parts of the respirator, like the straps or the nose foam.

The same measures taken to not contaminate new respirators have to be taken when using decontaminated ones. This includes washing the hands before and after handling them, and always doing so by the straps and not by the facepiece.

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