Does the type of mask matter?
Studies have compared various mask materials, but for the general public, the most important consideration may be comfort. The best mask is one you can wear comfortably and consistently, said Chin-Hong. KN95 face mask is only necessary in medical situations such as intubation. Surgical masks are generally more protective than disposable mask, and some people find them lighter and more comfortable to wear.
The bottom line is that any mask that covers the nose and mouth will be of benefit.
“The concept is risk reduction rather than absolute prevention,” said Chin-Hong. “You don’t throw up your hands if you think a mask is not 100 percent effective. That’s silly. Nobody’s taking a cholesterol medicine because they’re going to prevent a heart attack 100 percent of the time, but you’re reducing your risk substantially.”
However, both Rutherford and Chin-Hong cautioned against KN95 masks with valves (commonly used in construction to prevent the inhalation of dust) because they do not protect those around you. These one-way valves close when the wearer breathes in, but open when the wearer breathes out, allowing unfiltered air and droplets to escape. Chin-Hong said that anyone wearing a valved mask would need to wear a surgical or cloth mask over it. "Alternatively, just wear a non-valved mask," he said.
San Francisco has specified that masks with valves do not comply with the city's face covering order.