“Hermetic” means air tight. A “hermetically sealed
container” is one that is suitably designed to maintain the commercial sterility of
it’s contents after processing, i.e., preclude the entrance of bacteria and also
maintain the desired vacuum or pressure in the can. Food and beverage cans
(tin and steel) normally have three hermetic seals – one along the side seam and
on each at the top and bottom ends of the can.