Q “Heard on the news that hospitals are running out of KN95 masks, but I saw a Stanford study saying they can be washed, would that be a solution to the shortage?” asks Pierre Chartrand, from Montreal.
A The latest news is that there is currently no shortage of KN95 masks in Quebec, but authorities are preparing for this eventuality, as they are everywhere in the world.
The N95 mask is used to protect healthcare professionals from contact with pathogens in aerosols produced by individuals infected with viruses or bacteria. It is made of polypropylene. It generates static electricity that allows it to trap very small particles, up to 0.3 micrometers in diameter. A respirator mask is called KN95 when it meets the standard set by the American National Institute for Occupational Safety and Health (NIOSH). To be approved, it must be able to filter at least 95% of particles in the air free of oil (hence N) when tested with particles 0.3 micrometers in diameter. It needs to fit very tightly to the face and is not effective if the person has a beard.
The mask should be replaced at most every eight hours, or when leaving a high risk area, or when it becomes too inconvenient for breathing. According to NIOSH, there is no way to determine whether a mask is still effective or not, and many parameters can influence how quickly it might lose effectiveness: ambient contamination, temperature and humidity, the fact that the person wearing it touches the mask more or less with more or less contaminated hands or gloves, etc.
As part of its pandemic preparedness work, NIOSH issued a comprehensive advice on best practices for saving masks, which many people now use as a benchmark. The American Centers for Disease Control and Prevention (CDC) also propose a strategy to adopt in the current context.
The study you are talking about is actually a real-time knowledge assessment carried out by medical researchers at Stanford University to help anesthesiologists in their decision-making in the context of COVID-19. The version I checked out is from March 25, but it's worth checking for updates. Their first advice to caregivers: follow the guidelines of their hospital.
An effective washing method for masks must both destroy the virus on the mask, be non-toxic to the wearer of the cleaned mask, and not damage the mask's ability to filter particles.
Stanford researchers report in a table the tests carried out recently by the company 4C Air with different techniques. Spending the mask for 30 minutes in hot air at 70 degrees, or 10 minutes in boiling water vapor appears to be effective in clearing the virus, and preserving the mask's ability to filter air. Disinfection with chlorine or alcohol, on the other hand, has greatly reduced the effectiveness of the masks, and researchers tell anesthetists not to do it.
They also report the results of a study published in 2009 on five methods of decontaminating N95 masks - proof that the subject has been in the air, so to speak, for quite some time. The researchers then tested in particular the decontamination by treatments with microwaves, chlorine, hydrogen peroxide, UV and ethylene oxide, but without evaluating the residual viral load.
This is all subject to change, however, as two studies do not constitute very strong evidence.
Last Friday, the Journal of the American Medical Association appealed to the scientific community to quickly carry out new studies on this subject and scientific publications are likely to multiply rapidly, because the stakes are high.
In summary, therefore, yes, there are probably effective methods to reuse masks, only, as of today, we do not yet have the reliable data that would allow us to identify the best technique, but that s 'comes.
