Snug face seals and breathability: N95 is your best mask

Written by Danielle Chiriguayo, produced by Brian Hardzinski

N95, KN95, and KF94 masks differ in where they’re tested and approved, and what type of straps they have, says Dr. Abraar Karan, infectious disease physician at Stanford University. Photo by Shutterstock.

The CDC is considering updating its mask guidance and may recommend Americans use high-filtration masks. That’s because cloth alone isn’t as effective against the highly contagious Omicron variant. But there’s a lot of confusion around masks — what’s the difference between N95, KN95, and KF94? Is double-masking with a cloth and surgical mask effective?  

A quality mask is one that’s comfortable, has a good seal, and is approved by the National Institute for Occupational Safety and Health (NIOSH), says Stanford University infectious disease physician Dr. Abraar Karan. Despite messaging from federal agencies that any mask is good enough, he emphasizes the need for the best available face coverings.

“As you have a more contagious variant … the primary way that the virus travels is through aerosols. These are small particles that float around in the air,” Karan tells KCRW. “They can infect you more effectively close up, but even further than six feet. They can hang around for more than 15 minutes. And these N95 masks are specifically designed to capture these particles based on how the mask itself was designed.”

The best mask and how to prolong its use

Karan highly recommends 3M’s 9205+ N95 masks because they are both comfortable and can provide the protection you need. 

He points out that masks use an electrostatic charge, which enhances its ability to filter out particulate matter, meaning quality masks can be used for 24-48 hours, as long as its filter isn’t wet or damaged. 

“[It isn’t] how long you've owned the mask, but how many hours you've actually worn the mask,” he explains. “Right now, if you were to get 10 masks and you could rotate one per day and then leave the others up to hang, you could really use this pack all the way through this surge and beyond.”

Mask differences

N95, KN95, and KF94 masks differ in where they’re tested and approved, and what type of straps they have. He notes that N95s are tested in the U.S. and have two straps that go around the back of your head. KN95 are from China and KF94 are from Korea, and they typically use earloops. 

When deciding which to use, Karan says it's important to do a seal test, ensuring there’s a good fit around the bridge of the nose and at the bottom of the mask. 

If double-masking, he says to make sure a cloth covering fits securely over a surgical mask. And while you may have a better fit around your nose and mouth — pushing filtration efficacy between 60-80% — he notes that breathability drops. 

“You have better breathability with N95 masks and you’re not leaving it up to people to just figure out what to do,” Karan says.



  • Dr. Abraar Karan - infectious disease physician and researcher at Stanford University