Face masks have officially entered intervention canon, which means now might be a good time to review all the relevant data. Although donning makeshift masks is better than traveling with your mouth and nose completely exposed, the degree to which you are protected against viral debris depends on material and structure.
SARS-Cov-2 fomites are incredibly small, with an average diameter of 0.1 micrometers. If you yourself are not infected and intend on making a mask from fabrics lying around your home, The CDC and Wake Forest University experts recommend two layers of tightly woven 100% cotton fabric, a double layer of cotton with a thread count of at least 180, or a double layer of normal cotton with a layer of flannel in between. SARS-Cov-2 remains active on cotton for about 24 hours.
While traveling, you want to apply enough layers of durable material to filtrate active droplets from orifices without diminishing breathability. Surgical masks, though limited in supply, strike this balance the most effectively.
In a new analysis published in the Lancet, researchers determined the length of time that SARS-Cov-2 survives on various surfaces at room temperature—including the non-woven fabric most surgical masks are composed of.
The authors suspected that those with access to medical masks tend to behave less cautiously, namely by touching and adjusting their masks during high-risks scenarios
Unless you make a point to routinely disinfect your masks with products composed of 60% alcohol, 62-71% ethanol, 0.5% hydrogen peroxide or 0.1 % sodium hypochlorite, the coronavirus that causes COVID-19 can remain active on the outer layer of surgical masks for up to a week.
“This is exactly why it is very important if you are wearing a surgical mask you don’t touch the outside of the mask, because you can contaminate your hands and if you touch your eyes you could be transferring the virus to your eyes,” Malik Peiris, a clinical and public health virologist, told the South China Morning Post.
Temperature is almost as influential as material as far as the virus’s stability is concerned. SARS-CoV-2 appears to be extremely stable at 4°C. At this temperature, the virus’s infectious potential diminishes very slowly and is even detectable after two weeks.
Conversely, when the researchers increased incubation temperatures to 70°C, the time for virus inactivation decreased to five minutes.
It’s important to remember that just because viral culture can be detected on a surface it doesn’t necessarily mean that said surface is highly infectious. Although SARS-Cov-2 droplets remain active while airborne for up to three hours, it becomes increasingly less infectious with every passing minute; saying nothing of the other salient factors that either bolster or neutralize its genetic integrity.
The same is true of surfaces. SARS-Cov-2 can live on many different materials for various lengths of time, but a series of substrates further dictates the risk of causal contact.
“No infectious virus could be recovered from printing and tissue papers after a 3-hour incubation, whereas no infectious virus could be detected from treated wood and cloth on day 2. By contrast, SARS-CoV-2 was more stable on smooth surfaces. No infectious virus could be detected from treated smooth surfaces on day 4 (glass and banknote) or day 7 (stainless steel and plastic),” the authors continued.
Still, with so many variables left undetermined, it’s advisable to err on the side of caution.
Common household disinfectants can deactivate the protective envelope encasing SARS-Cov-2’s genetic material. To facilitate reuse, be sure to properly disinfect surgical masks with any of the substances previously indexed and wash homemade cotton masks after every use with soap and hot water.