GORE® Automotive Vents Glossary

United States

Glossary of terms and definitions related to GORE® Automotive Vents.


The volume of air passing through the vent, at a particular backpressure (usually measured per unit time). The amount of airflow required is based on housing size, anticipated temperature ranges, altitude changes, and allowable pressure differentials. Gore has developed computer modeling programs to help determine the amount of airflow required.


Any material laminated to an ePTFE membrane to improve the functionality of the vent. Typically, a backer will improve puncture strength and stiffness. In addition, a backer can be selected to act as adhesive for use in heat welding applications.

Chemical Resistance

Expanded PTFE is chemically resistant to virtually all industrial chemicals, including acids, alcohols, aledhydes, amines, bases, esters, ethers, halogenated hydrocarbons, hydrocarbons, ketones, polyalcohols and many more. For specific information please contact a Gore representative.


The phase change of water moving from the vapor phase to the liquid phase In an automotive applications, condensation generally occurs when the dew point exceeds the ambient termperature.

Dew Point

The temperature at which water vapor will condense out of the air.


The migration of substances from regions where their concentration is high to regions where their concentration is low. Airflow is not required for diffusion to occur. GORE Automotive Vents take advantage of diffusion by allowing moisture to diffuse out of headlamps (typically of higher moisture concentration) to reduce condensation.


ePTFE: expanded Polytetrafluorethylene Expanded polytetrafluorethylene, or ePTFE, was invented by W.L. Gore & Associates, Inc. more than 30 years ago. Gore discovered that PTFE, a polymerized tetrafluoroethylene known for its chemical inertness, high thermal stability, low coefficient of friction and other distinctive properties, could be stretched rapidly to create a strong microporous material known as expanded PTFE, or ePTFE. The unique structure of the GORE® Membrane is ideally suited for venting applications because of its ability to repel liquids and other contaminants while allowing air to flow through its microporous structure. In addition to GORE Automotive Vents, Gore has incorporated its proprietary ePTFE technology into thousands of diverse products.


Membranes that repel water. ePTFE is naturally hydrophobic.

Ingress Protection (IP)

Ingress Protection standards according to IEC (International Electronical Commission)


A laminate is a multi-layer construction. ePTFE membranes can be bonded to backing materials to change properties like durability, penetration resistance, stiffness etc.


GORE® Membranes are thin films of porous ePTFE. The porous nature of ePTFE allows air and vapors to pass, but restricts the passage of larger substances like dust, dirt and liquid water.

Moisture Vapor Transmission Rate (MVTR)

The rate at which moisture diffuses through a material.


Membranes that are able to resist low surface tension fluids. In an automotive application, there are many low surface tension fluids including gasoline, engine oil, transmission fluids, brake fluids, antifreeze, windshield wiper fluid, and car wash/wax solutions.

Pressure Sensitive Adhesive (PSA)

An adhesive that is designed to bond through installation pressure. Typically, the adhesives have low initial tack to allow handling, but when pressure is applied to the adhesive, it begins to creep into the microstructure of the housing material. The adhesive gains over 90% of its bond strength in 24 hours and comes to full strength within a week.


Polytetrafluorethylene is used across a wide range of functions in many markets and is the building block of expanded PTFE or ePTFE. PTFE is one the most versatile thermoplastics known to the world. It is a polymerized tetrafluoroethylene known for its chemical inertness, high thermal stability, low coefficient of friction and other distinctive properties. Gore invented and continues to specialize in the research and manufacture of ePTFE, a microporous version of PTFE. Expanded PTFE, or ePTFE, offers a range of different and desirable properties which the company has utilized in thousands of diverse products.

Pressure Equalization

GORE Automotive Vents constantly equalize the difference in pressure between the inside of the housing and the outside environment. As the structure heats and cools, pressure is built and released by the vent, eliminating any stress on seals maintaining equal pressures between the inside and outside of your enclosure may help extend product life.

Water Entry Pressure (WEP); iWEP and eWEP testing

iWEP and eWEP: What’s the Difference?

iWEP (Instantaneous WEP Testing) is a Water Entry Pressure test in which water is forced, with increasing pressure, against one side of the vent membrane until the first droplets penetrate the opposite side of the membrane. This test measures “how much pressure” the membrane can withstand before water penetrates it.

eWEP (Extended WEP Testing) provides more information than iWEP Testing, because eWEP measures both “how much pressure” and “for what duration of time.” For example, a given vent may have a minimum WEP rating of 110 kPa for 300 seconds. An eWEP test can confirm that the membrane does withstand the specified pressure/time without failure. This would indicate that the product is likely to perform reliably when exposed to similar environmental challenges during real-world operating conditions.

To evaluate Water Entry Pressure resistance, Gore typically conducts BOTH eWEP and iWEP validation testing. This enables us to more thoroughly assess product performance, and ensure that our products will do what we say they will do.


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