N95 masks, also known as N95 respirators have been the most popular and available respirators around the world before the pandemic. They don’t only filter out viruses like the flu, but also smoke and dust. Since the pandemic began, they’ve been considered the best disposable face masks for antiviral purposes, offering more virus protection than most face masks available out there.
These masks, which were once available for anyone to buy in bulk and wholesale and people could find them for sale online easily, have now been scarce in most states in the USA. The country has been going through severe shortages of medical PPE (personal protective equipment), which has been affecting healthcare centers. Some of the scarcest supplies include gowns, gloves, face shields, surgical masks, and KN95 masks.
But, the most affected product has been the N95 respirator, a crucial item for the protection of healthcare workers in the United States. This is why we want to talk about the best sterilization techniques for them.
PPE can be reused after decontamination in situations where supplies are limited to maximize their lifespan. However, certain strategies can be implemented before sterilization and limited reuse of N95 masks to achieve this, and need to be considered first. Just as an example, the use of expired equipment can be done in times of emergency like the one we’re facing, since the approval by the Food and Drug Administration (FDA) can still apply to them. So, expired respirators can be considered functional during these situations.
The main strategies to implement during a respirator shortage before the sterilization and limited reuse are:
Minimizing the need for these supplies: this includes all the measures that can be taken to reduce the need for PPE overall, considered to be the first measure to be taken. If this isn’t possible to achieve, prolonging the lifespan of the existing supplies can be considered as well, and the strategies to achieve this are:
- Reserving PPE only for patients with COVID-19 in which direct contact is required. Barrier precautions can be used on their own for source control.
- Elective or non-COVID-19 procedures that may require PPE can be canceled when possible.
- When contact isn’t necessary, separating staff from patients has to be done as much as possible, using engineering controls like shields and other types of physical barriers. This minimizes the paths that lead to infection.
Rotating the existing PPE stock: it’s been shown that the SARS-CoV-2, the virus responsible for COVID-19, has a relatively short half-life inside the filter material used in respirators. This led to the CDC (Centers for Disease Control and Prevention) developing a strategy to reduce the need for sterilizing respirators based on rotating the existing ones under the principle of the medium life the virus has on them. The strategy includes the following steps:
- Healthcare workers are given five respirators, assuming they have a five-day work shift.
- The worker uses one respirator during the entire workday, and at the end, it’s removed and stored in a breathable paper bag. The respirator is left there for one week.
- The next day, the same thing is done with a different respirator.
Between two uses of the same respirators, seven days pass, which is considered enough time for the virus to become inert in the filter media. These respirators must be handled as if they were contaminated nonetheless. The uncertainty surrounding this new virus leads to there still being doubts about their half-life, so precautions need to be taken when putting them on.
After these strategies are implemented and there are still shortages of respirators, healthcare centers can begin to consider the decontamination and limited reuse of their PPE. The CDC has a guide for decontaminating and reusing these respirators, which they call FFPs (filtering facepieces) or FFRs (filtering facepiece respirators).
Their guidance isn’t definitive or universal, since they clearly state that, when available, the guidance of the manufacturer for that specific respirator model has to be followed. 3M N95 masks, with popular models being 3M 8210 and the 3M 8511, can be decontaminated following these recommendations. In April, 3M updated their recommendations for decontamination, and these would supersede the CDC guidelines.
According to the CDC, an effective decontamination system or process has to:
- Not damage of the filter material
- Not affect the fit of the facepiece
- Inactivate the target organism in the facepiece effectively
They also mention the three most promising methods for sterilization, which are ultraviolet germicidal irradiation, vaporous hydrogen peroxide, and moist heat. These methods can be applied to any type of medical PPE, but after testing, they are great options for FFRs as well. As we mentioned, each method has to be evaluated taking into consideration the specific FFP model, as well as the guidance of the manufacturer or third-parties when these aren’t available.
Ultraviolet germicidal irradiation: exposure to this agent can be used simultaneously in many masks to decontaminate them. An entire room is set with UV lights, and both sides of the mask need to be exposed to them. Monitors make sure the proper dose is being used, and this takes only about 15 minutes, being the fastest method among the three.
Vaporous hydrogen peroxide: many hospitals already have the machines that perform this type of sterilization, in which FFPs are gassed with hydrogen peroxide vapors for 45 minutes. Respirators can endure about 50 cycles of this sterilization method.
Moist heat: respirators are exposed to temperatures of about 65 to 80 degrees Celsius and a humidity level of between 50 and 80%. Multiple cycles are needed, and it’s the one that produces the most damage to the respirator, but it can be more efficient than exposure to UV light.
After being sterilized using these methods, using PPE has to be done with extra precaution and infection control. Some measures include:
- Checking the fit of the mask every time it’s going to be used
- Checking if there’s been degradation on the nose foam or the straps before using them
- Regular measures, like washing the hands before and after handling it, or not touching the inside of the respirator