Both fit and filtration are important in choosing a good mask, but most people only consider one or the other.
If your mask fabric is bad, it can’t protect you, and that’s why we spend so much time talking about filtration efficiency. However, it’s important to note that we are just testing how well the fabric does in our lab—it will be different on your face.
If there are large air gaps on the sides of your mask, or if the nose wire doesn’t give you a good seal, those are all areas where things like COVID can get in. Air is like water and will find the path of least resistance, which is why having a well-fitting mask is as important as a mask with filtration above 95%.
Why have we tested over 400 masks for filtration efficiency? (See our Mask Testing Database). Because we figure that most people can put on a mask, check for air gaps, and see how well it fits them. However, most don't have a $250K mask lab to make sure the fabric is good—that’s where we come in.
We are just solving for the filtration quality and letting people figure out the fit.
NIOSH, when testing for the N95, wants a manufacturer to account for nine different face shapes. But, we’ve found that there are almost 30 different face shapes out there. That means different masks will fit you better than others. It's also why we created our Mask Sampler Kit to let people try on different masks and respirators without spending thousands on masks.
For example, our USA-made ASTM 3 surgical mask has fabric that is tested to filter above 98%, but depending on your face shape and size, your fit may decrease that filtration efficiency anywhere from 80% to 60%—although one large study has concluded that surgical masks significantly reduce the spread of COVID-19.
Fit is important, but so is filtration material. Both are very important in choosing a quality mask, so make sure you consider both before making a purchase.