Breather Plug
A breather plug is an element with an ePTFE membrane that passes air but not liquid water, used to equalise the internal and external pressure of a sealed enclosure. By removing the pressure difference created by temperature change, it prevents the gaskets from drawing in humid air and condensation from building up inside the enclosure.
When a closed enclosure warms up, the air inside expands, and when it cools it contracts. The low pressure created during contraction draws the humid outside air in through the weakest point of the gaskets. Because this cycle repeats every day, the enclosure accumulates water over time even if it has no leak at all.
- How it works: the porous ePTFE membrane lets air molecules through, while the surface tension of a water droplet prevents it from passing through the pore.
- Where it is fitted: in the upper region of the enclosure, at a point not exposed to a direct water jet.
- Alternative: breather cable glands that carry the same membrane in their body.
Receiver boxes, driver housings and field junction boxes working outdoors are the group that benefits most from this element. To keep the membrane from clogging, do not cover the plug with paint, grease or adhesive; check that its surface is clean during periodic maintenance.
Context in which this term is used: Installation, redundancy and field continuity