The Fixation Masks by Shannon Dunbabin use Fixation, a stretchy cotton/elastic blend. The Double Layer mask includes an opening to allow a filter. You can use Fixation alone or with cotton such as Ultra Pima . Fixation I-cords make perfect ear straps! The elastic in Fixation helps to ensure a more secure fit. 

Don't need a double layer? A pattern for the single layer is available here.

The masks are knit using size US 4 needles. 

This pattern is available as a PDF download.