An open leak path differs from transport through material
- Permeation
The substance travels through intact material rather than a visible hole. Identify fluid, temperature, thickness and driving difference.
- Permeability / permeance
Permeance describes transport through the layer; permeability additionally normalizes thickness under the stated model. Match units and conditions.
- Water vapor transmission rate (WVTR)
WVTR relates water-vapour mass to area and time under specified conditions. Liquid-water protection does not state this quantity.
- Leak rate
Fluid passes the gap between mating parts. Specify the test medium, pressure difference, reference conditions and units.
- HermeticityThis term
The complete boundary is evaluated against its stated leak requirement. A filled joint or an IP rating does not by itself establish hermeticity.
A gap can pass fluid as leakage, while an intact material can transmit a substance by sorption and diffusion. Transport quantities require stated area, thickness, driving difference and conditions.
Conceptual transport paths. These illustrations specify no leak limit, permeability value or conversion between gas, liquid and water-vapour tests.