Many experts are now recommending people upgrade from a cloth mask to a more protective N95 or other similar respirators to better protect against the COVID-19 omicron variant sweeping through the United States.
But how long can someone wear an N95 mask that clearly states "single use" on the label?
"I wear mine for a week," Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, said.
N95 masks provide highly efficient filtration against airborne particles, up to 95% according to the National Institute of Occupational Safety and Health.
She went on to say that an N95 mask's materials aren't "going to degrade unless you physically rub it or poke holes in it," Marr said. "You'd have to be in really polluted air ... for several days before it lost its ability to filter out particles. So, you can really wear them for a long time.
"People have been talking about 40 hours -- I think that's fine. Really, it's going to get gross from your face or the straps will get too loose or maybe break before you're going to lose filtration ability," Marr said.
These higher-quality masks are labeled as "single use" because they are categorized as medical masks, according to Erin Bromage, an associate professor of biology at the University of Massachusetts Dartmouth.
"When you then take a medical-grade thing that's single-use and put it in the general public, we're not worried about you cross-contaminating different environments you're being in. It's really about providing protection to you," Bromage said.
He pointed out that N95 masks "used to be only $1 or so each" but prices have increased with the public demand for a more protective mask amid the omicron variant's surge. Bromage went on to give a hypothetical example of how he would approach reusing a mask.
"[If] I was working in an office and I was wearing an N95 and someone in my office had tested positive, I'd know I was well-protected," Bromage said. "But I'd probably throw out that mask. Because that mask has done its job of trapping the virus and I don't even want to take the risk of it being there and getting on my hands or whatever."
He said that if the mask becomes damaged, wet, or visibly dirty then it's probably time to switch to a new one. The conditions could decrease the mask's effectiveness, and added that you shouldn't wash the mask to clean it.
"The longer you wear it, the more it's actually trapping material -- which means that the breathability, the resistance of the mask, starts to decrease," Bromage said. "One of the first indicators of being able to change it if it looks nice and clean is that it just feels a little harder to breathe through. There appears to be more resistance with every breath."