To prevent oxidation, mold growth, spoilage, insect repellent, and bacteria growth.
The vacuum part of the sealer removes all oxygen from the package and the gas flush part replaces the oxygen with a gas solution (Usually a mixture of nitrogen and carbon dioxide). This process changes the atmosphere and pH your product.
Reducing oxygen levels from packaged food products limits the growth of bacteria and fungi, thus extending the expected life of the product. Replacing oxygen with the appropriate gas may further extend shelf life.
The Gas Flush Kit can easily be turned OFF, if you use the machine for normal sealing. There is no any disadvantage of having a gas flush kit installed even if you do not use one.