(1) Depth of the air cell (air space between shell membranes, normally in the large end of the egg). The depth of the air cell is the distance from its top to its bottom when the egg is held air cell upward.

(2) Free air cell. An air cell that moves freely toward the uppermost point in the egg as the egg is rotated slowly.

(3) Bubbly air cell. A ruptured air cell resulting in one or more small separate air bubbles usually floating beneath the main air cell.