The conditions under which the measurement is made has a considerable influence on the result. Both the temperature and humidity gradients across the sample need to be measured, controlled and recorded with the result, and the thickness of the sample should be the same. An MVTR result without specifying these conditions is almost meaningless. Certainly no two results should be compared unless the conditions are known. For example, the effect of temperature on the permeability can be as high as 10\% per degree centigrade, making  results achieved at 23°C and 37°C  differ by a factor of 3.8.
The conditions under which the measurement is made has a considerable influence on the result. Both the temperature and humidity gradients across the sample need to be measured, controlled and recorded with the result, and the thickness of the sample should be the same. An MVTR result without specifying these conditions is almost meaningless. Certainly no two results should be compared unless the conditions are known. For example, the effect of temperature on the permeability can be as high as 10\% per degree centigrade, making it possible that results achieved at 23°C and 37°C can differ by a factor 4.
A
it possible that
A
can
R
of 3.8.
4.