N95

“One-way masking works,” Dr. Amesh Adalja, an infectious-disease specialist at Johns Hopkins University, said. When he is treating tuberculosis patients, they are typically maskless, and he wears an N95 mask to protect himself.

Unlike cloth masks, high-quality masks — called N95s, KN95s and KF94s — are made with layers of high-tech filtering material that trap at least 94 to 95 percent of the most risky particles.