The US Centers for Disease Control and Prevention has changed its mask guidelines to recommend that people “wear the most protective mask you can that fits well and that you will wear consistently.” The agency describes well-fitting respirators approved by the National Institute of Occupational Safety & Health (NIOSH) — such as N95 masks — as offering “the highest level of protection.”

The updated guidelines come after many public health experts have been recommending for months that people wear more effective masks — particularly N95s — and that the CDC change its guidelines on mask-wearing.

“Cloth masks are little more than facial decorations. There’s no place for them in light of Omicron, Dr. Leana Wen, an emergency physician and visiting professor of health policy and management at the George Washington University Milken Institute School of Public Health, recently said.”

In crowded places, “you should be wearing a KN95 or N95 mask,” which can cost a few dollars each, Wen added. Due to certain materials — such as polypropylene fibers — acting as both mechanical and electrostatic barriers, these masks better prevent tiny particles from getting into your nose or mouth and must be fitted to your face to function properly.

Here’s what you need to know about masks like N95s, where to get them and how to use them safely.