Air cell

The pocket of air found at the larger end of the egg. It is easily observed at the flattened end of a peeled, hard-boiled egg. When laid, the egg is quite warm and filled with liquid. As it cools, the contents contract, and the air cell is created. The air cell increases in size as the egg ages and air enters by way of the pores, replacing the original moisture and carbon dioxide that escape as time passes. The size of the air cell is one means used for determining the commercial grade of an egg.