Water Vapor vs. Water

Confusion often arises when discussing Immersion Proof Breathers and their performance when subjected to water vapor and immersion in water.  The hydrophobic properties of the membrane prevent the breakthrough of liquid water, but allow the continuous permeation of water vapor.

Other gases with a similar molecular size (~3.1Å or less) to water vapor also permeate through the membrane.
Plastic Immersion Breather