Keeps the dust out.
I am an archaeologist with asthma and during the field season I inhale a lot of dust. At the end of the day the stuff I blow out of my nose is the black crude that has been accumulating all day and at night I snore and have difficulty breathing. Once I started wearing this mask, things got a lot better. It takes a little getting use too, but after the first half hour of the day I hardly notice it. The wire that pinches the mask to the bridge of my nose also keeps my breath from fogging up my glasses. It took a day or two to figure it out but, I have not had a problem since.
Rating: 5 stars