The N95 respirator masks that have become so crucial for health workers (and citizens who want the best available mask) -- but six months into the pandemic, we're still suffering severe shortages.
Now, a group of researchers believe they've found a cheap and simple way to disinfect the N95, allowing them to be worn several times, potentially alleviating the shortage.
When it comes to face masks, the N95 (or other similar respirator masks) are pretty much the best you can get. But while they offer better filtration, they're also more expensive and less available to the general public. For day-to-day practical purposes, other types of masks can do well enough, but if you work in a clinical setting, having access to the best protection available is crucial.
Now, researchers at the Department of Energy's SLAC National Accelerator Laboratory, Stanford University, and the University of Texas Medical Branch have found a way to alleviate this respirator mask shortage. According to them, a combination of moderate heat and high relative humidity can disinfect N95 masks without affecting their ability to filter out viruses.
The paper's authors, which include Nobel laureate Steven Chu, found that heat treatments of 75˚C for 30 min or 85˚C for 20 min at 100% relative humidity resulted in efficient decontamination of SARS-CoV-2, as well as other RNA viruses such as the common cold and chikungunya viruses, without lowering the fabric's filtration efficiency. They trialed temperatures ranging from 25 to 95 degrees Celsius for up to 30 minutes with relative humidity up to 100 percent, but the sweet spot seemed to be between 75 and 85˚C -- any hotter and you risk degrading the material, any colder and you might not destroy all the viruses.
"This is really an issue, so if you can find a way to recycle the masks a few dozen times, the shortage goes way down," said Stanford physicist Steven Chu, senior author on the new paper. "You can imagine each doctor or nurse having their own personal collection of up to a dozen masks. The ability to decontaminate several of these masks while they are having a coffee break will lessen the chance that masks contaminated with COVID viruses would expose other patients."
The results are not particularly surprising because heat and humidity are known to be the banes of viruses. But finding the exact range of temperature, humidity, and time is valuable for hospitals to set their own disinfecting protocols.
According to results, the masks can be decontaminated and reused at least 20 times. Researchers say that even after this pandemic, the method could still be deployed to reduce waste and improve hospital efficiency.
Journal References: Rafael K Campos et al, Decontamination of SARS-CoV-2 and Other RNA Viruses from N95 Level Meltblown Polypropylene Fabric Using Heat under Different Humidities, ACS Nano (2020). DOI: 10.1021/acsnano.0c06565