Right now, hospitals are needing to buy N95 masks and other medical supplies, including gloves, gowns, face shields, and KN95 masks, in bulk and wholesale purchases to make sure their workers are protected. However, these items have been very difficult to find for sale in any online or physical store in the United States.
While the general public, including kids over the age of 2, can be protected using reusable cloth masks, healthcare settings represent a higher risk of exposure. This is why the main focus, at least in the USA, has been the development of decontamination methods.
Today, we’ll discuss steam sterilization for N95 masks.
Explaining N95 masks
N95 masks are considered the best option for virus protection in healthcare settings. These are disposable face masks with very specific antiviral filtering properties that have made them extremely valuable in hospitals and other healthcare facilities where the exposure to the SARS-CoV-2, the virus responsible for COVID-19, is very high.
This efficacy comes from the fact they can filter out a minimum of 95% of the airborne particles in the air the wearer is breathing. However, this efficacy is only applied to non-oil based airborne particles, since these masks are not resistant to oil. An airborne particle is that with a size of 0.3 micrometers, which allows them to travel through the air for long distances.
This makes N95 masks have multiple uses since particles with these characteristics are very diverse and can be found in many different types of work settings. For example, construction workers are often exposed to dust or smoke particles, and N95 respirators can be used in these environments. In healthcare settings, bioaerosols like the flu virus and right now the coronavirus can be protected against by using N95 masks.
Some of the most popular models are the 3M N95 masks, which can come in a wide variety of different modes. For example, the 3M 1860 is a surgical N95 mask, while the 3M 8210 is a regular one. The 3M 8511 has an exhalation valve, which makes them unsuitable for healthcare settings.
The difference between a regular N95 mask and a surgical one comes from the regulations and requirements they have to meet. To be considered a legitimate N95 mask, the National Institute for Occupational Safety and Health (NIOSH) has to test it and approve it. Additionally, for N95 respirators used in healthcare settings, the Food and Drug Administration has to approve them.
Steam sterilization for N95 masks
With the problem of shortages of all types of medical supplies, and N95 masks being particularly affected by this, all types of decontamination techniques are being studied right now in an attempt to alleviate this problem. Steam sterilization has been one of the most considered and questioned methods, but do they work on N95 respirators? We’ll discuss an article published in Consteril’s website.
An autoclave is a device that sterilizes equipment using steam, and has been proved effective, and is widely used in many healthcare settings, including dental offices, laboratories, hospitals, and others. Previous studies that aimed to experiment with the use of a steam autoclave in N95 masks have already suggested that it’s ineffective for this item.
But, with the surge of the COVID-19 pandemic, new studies have been performed that could potentially suggest the use of this device in N95 masks could be effective, and that previous studies maybe didn’t paint the whole picture. Although the CDC generally recommends other types of decontamination processes, like ultraviolet germicidal irradiation and hydrogen peroxide vapor, in many areas of the USA these technologies are either not available or too expensive.
One of the main concerns when using steam on N95 masks has to do with the electrostatic charges on the filter media of some N95 mask models that trap the particles with the opposite charge by attracting them. Moisture can eradicate these charges, which is why N95 masks have to be changed when they’re damp.
However, according to Peter Tsai, the co-inventor of the electrostatic N95 mask, steam, and condensate probably have very little effect on this electret. In a study published by him, he found that the masks showed no loss of the charges when exposed for 3 minutes to steam at a temperature of 250 ⁰F, which is the typical sterilization temperature.
Other data, on the other hand, show the contrary. A study made by the Texas Department of Medicine showed that 30 to 60 minutes of steam decontamination performed on a 3M 1860 mask, which contains an electret, made the efficacy of the mask drop below the 95% rate.
Another test performed by Nathan Bopp et al. in Texas showed that, after 3 autoclave cycles, the 3M 1805 and 1870 didn’t show any degradation of the filter activity with a temperature of 250 ⁰F for 30 minutes and 239 ⁰F for 60 minutes. This showed that a lower temperature decontamination for 60 minutes showed less degradation than a high temperature one for 30 minutes. But, all the masks dropped efficacy below 95% after one cycle, nonetheless.
The studies the article talks about also involve the viral inactivation of the SARS-CoV-2 specifically, since this is the main pathogen the techniques have to focus on right now. In the study, the masks were inoculated with the virus before being autoclaved and the viral growth was compared afterward. The four models the study used showed a total inactivation of the viral particles after autoclaving.
In conclusion, some of the studies performed on the masks with the electrect showed efficacy and some didn’t, and the masks without this filtration technology would be ideal for this decontamination process. They suggest that an autoclave test on the specific N95 mask model would be ideal before using it.
For more information and other studies mentioned in the article, you can read it here.