For the three-layer mask, the qualities that would follow the material specifications would be a mid-weight or lightweight non-woven, non-fusible, and high-polyester %.  


Having a non-fusible material is very important, because a melted adhesive could restrict airflow.  A heavyweight interfacing would similarly restrict airflow.  OLY-fun is polypropylene, which does not withstand the high of heat of the sanitizing process as well as the polyeser or polyester blend does.