What is the substance is for this mask (i.e. polypropylene, cellulose, etc.)? Is it chemical free? What is the difference between the two masks on this page?

The materials for this item are: Outer Coverstock: Lightweight spunbond polypropylene Secondary Layer: White Alpha soft PE/PET Filter Material: 100% MB polypropylene Inner Coverstock: White, lightweight, non-woven material Nose Band: Aluminum strip These are not chemical free. The antifog version has a strip along the nose piece to create a better seal to the face and prevent fogging of safety glasses.