MINNEAPOLIS — A mask only works if it's worn, and fits, correctly. So, how can you make sure your mask fits?
"If you're breathing very easy, one [way] that you can tell [it doesn't fit], is that maybe it's too easy [to breathe], and finding out where around the perimeter of the mask air is coming out," said Dr. Sara Zimmer, associate professor in the University of Minnesota Medical School's Biomedical Sciences Department.
Zimmer says when a mask fits properly it creates a sort of "seal" around your nose and mouth.
"So, that most of the air is directed through the mask filtering capacity, which is really what we're after," she said.
Here's why that "seal" is important. A study published by the American Chemical Society found homemade masks made out of a combination of high thread cotton and silk blocked 98% of big droplets and 94% of smaller ones.
But if that same mask had gaps on the side, the study found it blocked only about 35% of all particles.
"The better seal that you get around [the mask], the less likely that air is just going to flow out of your mouth [unimpeded]," Zimmer said. "If you feel air coming out, and you make an alteration on your mask and you no longer feel that, you've made a difference."
Zimmer said most masks require some sort of modification to fit correctly.
"It would great if we had this universal mask that everybody could wear and it would just always work, but our faces are really different," she said.
Those modifications can be simple. Zimmer says bands can be tightened and double-sided tape can be used to close a gap. She even recommends trying to use the plastic closure on a bag of coffee to make the mask better conform to the nose.
"Yeah, you get to be MacGyver," she said. "Nothing is going to make it perfect, but everything is going to help, and that's what we're after."
Zimmer says thread count matters, too. She says if you hold your mask up to a light and can see the light particles through the fabric, it's too thin. She says adding fabric or wearing two masks at once can help, but there is a risk of going too far.
"If you have too many layers on your face ... then you're going to be forcing air out the sides," she said. "So, there probably is a happy medium on how many layers you actually want to be wearing."
RELATED: What science says about masks