WVP is the mass of water vapor transmitted through a unit area in a unit time under specified conditions of temperature and humidity.

US permThe US perm is defined as 1 grain of water vapor per hour, per square foot, per inch of mercury.1 US perm = 0.659045 metric perms≈ 57.2135 ng·s−1·m−2·Pa−1Metric permThe metric perm (not an SI unit) is defined as 1 gram of water vapor per day, per square meter, per millimeter of mercury.1 metric perm = 1.51735 US perms≈ 86.8127 ng·s−1·m−2·Pa−1Equivalent SI unitThe equivalent SI measure is the nanogram per second per square meter per pascal.1 ng·s−1·m−2·Pa−1≈ 0.0174784 US perms≈ 0.0115191 metric perms

The base normal SI unit for permeance is the kilogram per second per square meter per pascal.

1 kg·s−1·m−2·Pa−1≈ 1.74784x10+10 US perms≈ 1.15191x10+10 metric perms

The answer of your question, is where you are reporting the unit. Most of scientific journals, they prefer SI unit. However, companies still prefer either US or Metric unit.

Dear Dr. Jasim Ahmed,

Thank you for the detailed and informative response.

water vapor permeability, g/(m∙s∙Pa)

Please find the attached article which answer the question

Regards

Just look up tables for WVTR ( water vapor transmission rate).

Most units are weight (gms), thickness( mils or micron), are ( mtsq, 100 inch sq) and time ( normally 24 hours)

basically how much weight "passes" per unit area of a given thickness in 24 hours

Please, i want knew how to convert water vapor permeability unit g/(m∙s∙Pa) to the barrer unit and (mole·m-1·s-1·Pa-1) unit

Would anyone answer me