Transparent thin film dressings are semi-permeable membranes that are waterproof, yet allow oxygen and water vapor to pass through. The dressings help fight bacterial contamination, and help maintain a moist wound environment. There are several new films on the market that offer very high Moisture Vapor Transmission Rates (MVTR). These films are directed more to the IV site market and not for chronic wounds. Thin film dressings are often used as a cover for a primary dressing.