3M - Half Facepiece Reusable Respirator - Medium. This half facepiece reusable respirator 7500 Series uses advanced silicone material to help provide comfortable and durable respiratory protection. The 3M Cool Flow Valve helps make breathing easier and can reduces heat and moisture build-up for cool, dry comfort.. The 3M Half Facepiece Reusable Respirator 7500 Series helps provide protection against particulates and a wide variety of gases and vapors when used with approved 3M cartridges and fil