Maximize Breath

Type: Metabreath
Source: Draconomicon

You can take a full-round action to use your breath weapon to maximum effect.
Prerequisite: Con 17, breath weapon.
Benefit: If you use your breath weapon as a full-round action, all variable, numeric effects of the attack are maximized. A maximized breath weapon deals maximum damage, lasts for the maximum time, or the like. For example, an old silver dragon using a maximized cold breath weapon (damage 16d8) deals 128 points of damage. An old silver dragon using a maximized paralysis gas breath weapon (duration 1d6+8 rounds) paralyzes creatures for 14 rounds if they fail their saving throws.
The DCs for saving throws against your breath weapon are not affected.
When you use this feat, add +3 to the number of rounds you must wait before using your breath weapon again.
This feat stacks with the effects of breath weapons enhanced with other metabreath feats, but does not maximize them. For example, a maximized breath weapon further enhanced by the Tempest Breath feat produces the type of wind effect noted in that feat description, but the velocity of the wind is not also maximized.
Special: You cannot use this feat and the Quicken Breath feat on the same breath weapon at the same time.