U.S. Food And Drug Administration

A large study run in Bangladesh claimed that surgical masks, but not cloth masks, reduced symptomatic SARS-CoV-2 infections" by 0.08% (ARR), and only in people over 50. But a subsequent re-analysis of the study by statisticians found that there was in fact no benefit at all.

People with chronic respiratory, cardiac, or other medical conditions that make breathing difficult should check with their health care provider before using an N95 respirator because the N95 respirator can make it more difficult for the wearer to breathe.

Despite not being regulated, there are ways for these brands and their manufacturers to increase their trustworthiness, like FDA registration or inclusion in the FDA's now-defunct emergency use authorization (EUA), which it passed in 2020 to help medical workers choose KN95 masks.

Bookmarks may or may not meet any fluid barrier or filtration efficiency levels; therefore, they are not a substitute for N95 respirators or other Filtering Facepiece Respirators (FFRs), which provide respiratory protection to the wearer, or for surgical masks, which provide fluid barrier protection to the wearer.