WVTR (WATER VAPOR TRANS RATE)

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WVTR (WATER VAPOR TRANS RATE)

WVTR (also referred to as MVTR, Moisture Vapor Transmission Rate), is a measure of the rate at which water vapor in the surrounding atmosphere will pass through a paper product. A specified relative humidity, % RH, is on one side of the sample and a desiccant is on the other side. The change in weight of the desiccant over time is a measure of the transmission of water vapor through the substrate. The test is usually run for 3 days, with a measurement taken each day. The water vapor transmission rate is calculated and is reported in g/m²/day.