Packaging Film Breathing Rate
Oxygen and Moisture are two key material specification properties which determine the shelf life of food packaging.
Oxygen Breathing Rate, (OTR) is the steady state rate at which oxygen gas can permeate through a film. OTR is expressed as a volume of oxygen that penetrates a given area in a one-day period; cc/m2/24hr
While Moisture Breathing Rate (WVTR), some called “moisture vapor transfer rate” (MVTR), is in other word the steady state rate at which moisture can permeate a packaging film, WVTR values expressed as g/m2/day
There is ASTM standard govern these test procedure. You can browse through internet for this up-to-date information