Sorting out the varieties of COVID-19 masks

February 4, 2022
3 min read

Dear Doctors: I want to upgrade from the cloth masks that our family has been using, but I’m confused. What’s the difference between N95, KN95 and KF94 masks? I’m sure a lot of people will find it helpful if you can explain the differences.

Dear Reader: SARS-CoV-2, which is the virus that causes COVID-19, is airborne. That means it travels not only on the somewhat sizable droplets that are released in a cough or a sneeze, but also on the ultrafine mist that is generated when someone speaks or even exhales. The smallest of these droplets can remain suspended in the air for minutes or even hours.

The use of masks has proven effective at blocking a large percentage of the particles that someone emits. We now also know that masks protect the wearer, as well. That’s why, with the advent of the highly infectious omicron variant, health officials are urging Americans to upgrade their masks.

N95 masks, also known as N95 respirators, are made of multiple layers of synthetic material that filter out 95% of particles as small as 0.3 microns. This can stop virus particles, which cannot travel on their own and are thus always bonded to something larger than themselves. The masks are also designed for a close fit around the face. N95 masks are regulated by the National Institute for Occupational Safety & Health, or NIOSH. At the start of the pandemic, N95 masks were scarce. Now, however, they are available from a number of manufacturers. The CDC maintains a list of approved N95 masks at its website. Go to and enter the words “NIOSH approved mask” in the search box at the top right of the page.

The KN95 and KF94 respirators are similar to the N95 mask in both materials and filtration. However, they are not made in the U.S. and thus are not subject to federal standards. The KN95 respirators are manufactured in China, and the KF94 models come from South Korea. Each meets its own nation’s regulatory standards. It’s important not to choose a respirator mask with a valve, as the exhaled air is unfiltered.

Elizabeth Ko, MD and Eve Glazier, MD

When a high-filtration mask isn’t available, three-ply surgical masks with adjustable nose clips are the next-best option. Cloth masks are most effective when they are made up of three layers of fabric with a tight weave.

With any type of mask, the fit is crucial. It starts with your mouth, nose and chin being completely covered. The fit around the perimeter of the mask should be snug enough to prevent gaps, which would allow unfiltered air to either escape as you exhale or enter as you inhale. A well-fitted mask with good filtration will “breathe” with you, slightly inflating and deflating in response to the changing pressure of your breath.

Wearing a mask for extended periods of time can be challenging. Just as we now know to take breaks from extended sitting at a desk, consider stepping outside for an occasional mask break. Be sure you’re safely away from other people, and mask up again before returning indoors.

To learn more about the vaccines and for the latest information visit UCLA Health's COVID-19 Vaccine Info Hub.

(Send your questions to [email protected] Owing to the volume of mail, personal replies cannot be provided.)