What is eVent® Fabric?
eVent Fabric is a Direct Venting™ waterproof barrier based on the next evolution of ePTFE laminate. Using a proprietary and patented Dry System Technology™, eVent fabric sets a new standard for comfort by allowing perspiration to dissipate and vent before it saturates the inside of the fabric. At the core of eVent fabric is a hydrophobic ePTFE (expanded Polytetrafluoroethelene) film that has been rendered oleophobic, and thereby free from body-oil contamination, via a method that retains the inherent open-pore structure of the membrane. The eVent family of fabrics are the smartest choice for athletes and adventurers who need and demand the highest possible performance and comfort from their garments.

Why a "wet system" can''t keep you dry.
Pure ePTFE film will become contaminated with certain oils (body oils, suntan lotion, etc.). These oils are attracted to the film and suppress its hydrophobic (water rejecting) nature. Once this occurs, the membrane ceases to be waterproof. Thus, to use ePTFE film in for waterproof apparel or footwear applications, it must be rendered oleophobic (oil repelling) so that contaminating body oils are not absorbed into the film. Traditionally, this has been accomplished by putting a thin, continuous layer of polyurethane (PU) over the surface of the ePTFE to keep oils out. However, this solution creates two new problems. First, it immediately gives up much of the inherent breathability of the ePTFE because the open pore structure is now covered. Second, because PU absorbs and retains moisture, the inside of the fabric quickly becomes, and remains, damp and clammy.

Finally… A Dry System!
eVent fabric utilizes a method of rendering ePTFE oleophobic without using water-retaining polyurethane and while retaining the open pore structure inherent in the material. This is accomplished with a molecular surface coating of the individual fibrils that comprise the open pore structure of the ePTFE material. With this Dry System, the sweated moisture vapor is not required to condense to liquid in order to escape the fabric. Instead, it vents directly to the outside of the fabric without first making the inside fabric wet.

Direct Venting vs. "Two-Step Moisture Transport"
Not only is eVent fabric a Dry System, but it also provides unprecedented levels of breathability. Previous ePTFE technology does not truly "breathe" but instead move moisture in two s-l-o-w steps through a process of moisture diffusion. First, sweated perspiration vapor condenses into the PU coating on the inside of the fabric, changing form vapor to liquid form. Then, body heat slowly forces that dampness through to the outside of the fabric where it can finally evaporate. In this system, moisture vapor must condense into liquid to pass through the PU layer.

Because the anti-contamination treatment used in eVent fabrics does not cover the ePTFE membrane with a polyurethane coating, all the pores in the material remain open, allowing them to breathe at their full potential. Sweated moisture vapor vents directly to the outside of the garment through a process called Direct Venting. www.eventfabrics.com

eVent is a Trademark of BHA Technologies, Inc.