How to correctly calculate the oxygen content in the packaging bag?

How to correctly calculate the oxygen content in the packaging bag?

Customers are very important in choosing deoxidizer specifications，the small size selection will result in the saturation degree of the oxygen absorption limit too early, making the product mouldy and deteriorating and shortening the prescribed shelf life，The large size selection has no effect on the product but increases the cost.     

The specific selection of deoxidizer specification is：（The packing material is under the condition of high barrier of oxygen to the material）
    Initial oxygen volumeV1=（Packing bag volumecm³-Food volumecm³）*21%（21% represents 21% of the oxygen content in the air）
   Oxygen volume in the osmotic package during the shelf lifeV2=Packing bag surface area(㎡)*Oxygen permeable rate of packaging bag（ml/atm·24h·㎡）*21%*Days of shelf life（21% represents 21% of the oxygen content in the air）,
     Oxygen uptake required by deoxidizerV= V1+ V2 
     The size of the deoxidizer is selected by the oxygen absorption required by the deoxidizer.

In the actual calculation, the oxygen permeable rate of the packing bag in V2 is difficult to be determined. Usually, the size of the deoxidizer is selected with the initial oxygen V1, and the model of deoxidizer close to V1 is selected.