Double red alert

Double-red alert was a rarely used alert signal for extremely dire situations, especially when a nearly instantaneous response was required. A double-red alert was technically equivalent to a red alert, except that it conveyed a higher sense of urgency. The alarms and lights for a double-red alert were the same as for a standard red alert.

Kirk once declared a double-red alert during off-hours, when Spock detected the distinctive sound of a phaser on overload hidden in Kirk's quarters. Realizing that there were only a few seconds available to evacuate that section of the ship, Kirk ordered a double-red alert.

Kirk remained in his cabin to search for the phaser, which, ironically, became visible when it was silhouetted inside the alert light fixture. Kirk was able to drop the phaser into an emergency disposal tube just before it exploded. 

Dubbel rood alarm