Researchers have confirmed that there are several effective methods for decontaminating the N95 masks worn by health professionals so that they can be used more than once, the National Institutes of Health announced Wednesday.

A substantial body of research already showed that the masks, designed for one-time use, can be reused in a crisis. And the Centers for Disease Control and Prevention in March authorized reuse because of shortages driven by the Covid-19 pandemic. In recent weeks the Food and Drug Administration has issued emergency approvals for several systems of mask decontamination.

None of these rules or methods are intended for the cloth masks recommended or in some locations required for use by everyone in public. The C.D.C. advises regular washing of homemade fabric masks in a washing machine.

Earlier research had not, of course, involved the new coronavirus. The new research, done at the Rocky Mountain Laboratories of the National Institute of Allergy and Infectious Diseases and used live novel coronavirus, formally known as SARS-CoV-2, to test the mask material. The study determined which decontamination procedures were most effective, and how they affected the integrity of the masks.