A breathable vent valve allows controlled airflow between a sealed enclosure and the outside environment while helping prevent water, dust and contaminants from entering. By reducing pressure differences caused by temperature changes, it protects enclosure seals and supports the long-term reliability of outdoor electronic equipment.

Xi’an Hoan Microwave Co., Ltd. supplies metal and plastic air vent valves for electronic enclosures and customized equipment applications. The company was established in 2005 and combines product development, manufacturing, quality control and technical support capabilities. 

Why Sealed Enclosures Need Pressure Equalization

A sealed electronic enclosure is not pressure-stable.

When internal components operate, they generate heat. Direct sunlight can also raise the housing temperature. The air inside expands and creates positive pressure. When the equipment cools at night, shuts down or is exposed to rain, the internal air contracts and creates negative pressure.

Repeated pressure cycling can place additional stress on:

enclosure gaskets; 

cable glands; 

covers and lenses; 

bonded joints; 

other sealing interfaces. 

Negative pressure may also draw humid air through small gaps or aging seals. A Waterproof Breather Valve provides a controlled route for air exchange, reducing this pressure load without leaving the enclosure directly open.

How Waterproof Breather Valves Work

A typical pressure equalization vent contains a housing, breathable membrane, airflow channel and sealing element.

When pressure inside the enclosure rises, air passes outward through the membrane. When internal pressure falls, air moves inward. This passive airflow gradually reduces the pressure difference between the enclosure and its surroundings.

The valve does not require electrical power, a fan or a mechanical actuator.

Its actual performance depends on several factors:

enclosure volume; 

rate of temperature change; 

membrane permeability; 

available membrane area; 

pressure differential; 

internal airflow resistance. 

A vent may match the mounting thread but still be unsuitable if it cannot provide enough airflow for the enclosure.

Why ePTFE Membranes Allow Air but Resist Water

Many waterproof vents use expanded polytetrafluoroethylene as the breathable medium.

An ePTFE Breathable Valve contains a microporous membrane that permits gas exchange while resisting liquid-water penetration under specified conditions. This allows the enclosure to breathe without using an unprotected ventilation hole.

Each part of the valve has a separate function:

The membrane material, airflow rate and water-resistance performance should always be confirmed from the specification of the selected model.

Metal Vent Plug vs Plastic Breather Valve

Both metal and plastic vents can provide pressure equalization.The correct choice depends on the equipment design and operating environment.

A threaded Metal Vent Plug is often selected for compact industrial equipment that requires mechanical protection and reliable fastening. Plastic vents may be more suitable where low weight, insulation or cost control is important.

Housing material should also be checked against corrosion, chemicals, oil, temperature and the material of the enclosure.

Typical Breathable Vent Valve Applications

Breathable vent valves are commonly used in outdoor and industrial electronic equipment exposed to temperature changes and environmental contaminants.

Outdoor LED lighting: Helps manage pressure changes caused by operational heating and nighttime cooling.

CCTV and monitoring equipment: Supports pressure equalization in camera housings exposed to sunlight, rain and changing temperatures.

Telecom enclosures: Protects communication modules, antenna controls and outdoor cabinets while allowing controlled airflow.

Outdoor sensors: Provides a compact pressure-management solution for small sealed instrument housings.

Industrial control boxes: Suitable for junction boxes, control modules and measuring equipment requiring threaded installation.

Vehicle-mounted electronics: Helps equipment handle rain, dust, vibration and rapid temperature variation.

Marine and coastal electronics: Can be used where humidity and salt exposure require careful material and corrosion-resistance selection.

Need Help Selecting the Right Vent Valve?

Thread size alone is not enough to choose a suitable vent.

Send HOAN the following project information:

enclosure dimensions or internal volume; 

thread or mounting-hole size; 

operating temperature range; 

required protection level; 

exposure to rain, dust, oil, chemicals or salt spray; 

estimated order quantity. 

How to Choose an IP68 Pressure Equalization Valve

An IP68 Pressure Equalization Valve must match the full enclosure design, not only the mounting hole.

Before selecting a model, confirm four key requirements:

Airflow

Larger enclosures or faster temperature changes generally require higher airflow. Insufficient flow may allow excessive pressure to remain inside the housing.

Waterproof protection

Rain, water jets and immersion are different exposure conditions. The required IP level should reflect the real application and corresponding test conditions.

Mounting interface

Check the thread diameter, pitch, wall thickness, sealing surface and available installation space.

Environmental compatibility

The membrane, housing and sealing ring must be suitable for temperature, dust, water, oils, solvents and corrosion exposure.

An IP68-rated vent does not automatically make the complete enclosure IP68. Final protection also depends on installation quality, sealing-ring compression and the structure of the finished housing.

Why Work with Xi’an Hoan Microwave Co., Ltd.?

Xi’an Hoan Microwave Co., Ltd. was established in 2005 and lists air vent valves as one of its official product categories. Its website also describes an internal design team, manufacturing capability, strict process control and a professional testing laboratory. The company supports customized product development and technical service according to customer requirements.

For vent projects, HOAN evaluates the application based on:

enclosure volume; 

airflow demand; 

installation dimensions; 

membrane requirements; 

housing material; 

IP protection; 

temperature and corrosion conditions. 

This engineering-based approach helps avoid selecting a product only because its thread size appears to fit.