The empty space between the white and shell at the large end of the egg.
- When an egg is first laid, it is warm. As it cools, the contents contract and the inner shell membrane separates from the outer shell membrane to form the air cell.
- The candler uses the size of the air cell as one basis for determining grade.
- In Grade AA eggs, the air cell may not exceed 1/8-inch in depth and is about the size of a dime.
- The air cell of Grade A eggs may exceed 3/16-inch in depth.
- For Grade B eggs, there is no limit on air cell size.
As the egg ages, moisture and carbon dioxide leave through the pores of the shell, air enters to replace them and the air cell becomes larger.
Although the air cell usually forms in the large end of the egg, it occasionally moves freely toward the uppermost point of the egg as the egg is rotated. It is then called a free or floating air cell. If the main air cell ruptures, resulting in one or more small separate air bubbles floating beneath the main air cell, it is known as a bubbly air cell.
You can see the air cell in the flattened end of a peeled, hard-cooked egg.