What is a Breathable Vent? PTFE & ePTFE Membrane Vent Explained

A breathable vent — also called a pressure equalization vent, breather vent, or PTFE membrane vent — is a small device installed in the wall of a sealed enclosure. It allows air pressure to equalize between the inside and outside of the enclosure while physically blocking liquid water, dust, oils, and contaminants from entering.

The core working principle is the ePTFE membrane: expanded polytetrafluoroethylene stretched into a microporous structure with billions of tiny pores. These pores allow individual air molecules and water vapour molecules to pass through freely — because they are very small — while blocking liquid water droplets and dust particles, which are much larger.

Why Do Sealed Enclosures Need a Breathable Vent?

Every sealed enclosure — whether an outdoor LED luminaire, an EV battery pack, a solar junction box, or an industrial control panel — contains a volume of air. When the enclosure heats up (from sun, from internal electronics, or from the environment), this air expands and creates positive internal pressure. When it cools, the air contracts and creates negative pressure.

This repeated pressure cycling — known as the breathing effect — stresses the enclosure's door seals and cable glands. Over months and years, the seals fatigue and begin to allow humid air past them as the enclosure exhales and inhales. The result:

• Moisture condensation on PCBs, connectors, and optical components
• Corrosion of metal contacts, busbars, and terminals
• Gradual loss of IP rating from IP68 down to IP54 or lower
• Premature product failure and increased maintenance cost

A breathable vent with ePTFE membrane eliminates this problem. It allows the pressure to equalize passively and continuously — without allowing any moisture or contamination through.

How Does an ePTFE Membrane Vent Work?

The ePTFE (expanded PTFE) membrane has a unique microporous structure. The membrane contains approximately 1.4 billion pores per cm². Each pore is approximately 0.2 microns in diameter — large enough for individual air molecules (0.0003 microns) and water vapour molecules (0.0004 microns) to pass through freely, but much smaller than a liquid water droplet (100+ microns) or a dust particle (1+ microns).

The membrane is also oleophobic — oil-repelling — so it resists clogging from oils, greases, and chemicals found in automotive, industrial, and EV environments.

This combination of properties means the vent:

• Allows: air, water vapour, gas molecules
• Blocks: liquid water, rain, dust, dirt, oil, chemicals
• Maintains: IP67 and IP68 rating of the enclosure

Types of Breathable Vents

Screw-In Vent Plugs (Threaded Vents)

The most common type. A brass or metal body with an external thread (M6×0.75, M12×1.0, M12×1.5) that screws directly into a threaded port in the enclosure wall. The ePTFE membrane is insert-moulded into the cap of the vent body. Used in outdoor enclosures, industrial panels, junction boxes, automotive ECUs, solar inverters, and EV battery housings.

Adhesive Membrane Vents (Stick-On Vents)

A self-adhesive ePTFE membrane patch applied directly to the interior surface of an enclosure wall. Used inside EV battery packs, consumer electronics, smart devices, and applications where a threaded port is not available or preferred.

Snap-Fit and Push-Fit Vents

Custom-configured vents for high-volume OEM applications where tool-less, snap-in installation is required. Available on request from Precigenix for specific enclosure designs.

What IP Rating Do Breathable Vents Provide?

A properly installed breathable vent maintains the existing IP rating of the enclosure it is fitted to. Precigenix breathable vents are tested and rated to IP68 — continuous submersion — which is the highest standard IP water ingress protection rating. They are also tested to IP54, IP65, IP66, and IP67.

Note that a breathable vent does not create an IP rating — it helps the enclosure maintain its designed IP rating over its service life by preventing seal fatigue from pressure cycling.

Which Applications Use Breathable Vents?

Breathable vents are used wherever a sealed enclosure is exposed to temperature changes, direct outdoor installation, or internal heat generation:

• Solar: solar junction boxes, combiner boxes, string inverters, solar charge controllers
• Automotive & EV: EV battery packs, BMS enclosures, OBC housings, motor controllers, ECUs, headlamp housings
• Industrial: electrical panels, control boxes, junction boxes, outdoor cabinets, ATEX explosion-proof housings
• Telecom: 5G base station enclosures, outdoor fiber boxes, OTN cabinets, network switch housings
• Electronics: LED luminaires, CCTV camera housings, IoT sensors, smart meters, outdoor displays

PTFE Vent vs ePTFE Vent — What's the Difference?

Solid PTFE is a dense, non-porous polymer. It does not allow air to pass through and cannot be used as a breathable vent membrane. ePTFE (expanded PTFE) is PTFE that has been mechanically stretched during manufacturing, creating a permanent microporous structure. It is this expanded, porous form that is used in breathable vent membranes. All breathable vents use ePTFE — never solid PTFE.

Learn more about the technical difference in our detailed guide: PTFE vs ePTFE Membrane Vent — What's the Difference?