Should I Make My Own Mask?

“I’ve been saying some protection is better than none,” said Dr. Marr, who noted that local health departments have been asking aerosol scientists for guidance on potential mask materials to deal with supply shortages. She said her team will have results soon with more specific recommendations for materials to use in masks.

Dr. Marr emphasized that most people do not need the high level of protection offered by a medical mask. “The potential for exposure is so much lower in a grocery store compared to working in a hospital close to patients,” she said.

Dr. Soe-Lin said she believes an added benefit of a mask is that it serves as a constant reminder against touching your face, a major way that the virus is spread. But no face covering, whether it’s homemade or a medical mask, makes you invincible. Pulling a mask on and off or fidgeting with it will lessen its effectiveness. And in theory, fiddling with your mask could contaminate it. Always remove a mask by the ear loops or the tie — never the part that covers your face. Dr. Soe-Lin said she has used cloth masks for three weeks and washes and dries them regularly. Someone with only one mask can hand wash at night and let it air dry. If a mask gets wet or damp while you are wearing it, it’s less effective, she said.

“I don’t think there is any evidence that this is going to make things worse, but there is evidence that it provides some additional good,” said Robert Hecht, professor at the Yale School of Public Health, who was the co-author of the face mask article with Dr. Soe-Lin. “Under this emergency situation we’re in, it seems, in our view, hard to argue against covering your face. We have large numbers of infections occurring which don’t need to happen if people were to use the masks.”

Dr. Mukherjee said he is hopeful that large companies and the government will produce and distribute inexpensive masks for essential workers like grocery clerks and delivery drivers, as well as the general public. Questions about durability, reuse and sanitizing masks, as well as the best fabric to use in a homemade mask, still need to be answered.

“My strong preference is for people to not cobble together homemade masks,” Dr. Mukherjee said. “People are using them because they are desperate, and they don’t know what to do.”

If you decide to start wearing a mask, you should know that it takes some getting used to. A mask can be hot and uncomfortable and fog your glasses if you wear them. But pulling it up and down defeats the purpose of wearing it.