A sheet material for use in packaging having at least a first layer and at lease a second layer, wherein the first layer and the second layer are bonded together to fabricate the sheet material such that an area between the first layer and the second layer is unbonded so as to create a passageway having at least one opening on a first side of the sheet material and at least one opening on a second side of the sheet material, the passageway being a one-way valve integrally formed by bonding together the first and second layers to form the sheet material.