A wildfire is designated as contained based on:

A wildfire is designated as contained when a certain percentage of the fire is held behind established control lines, which are designed to prevent further spread. The correct basis for this determination is the percentage of the fire that is kept behind these control lines, demonstrating that the fire has been managed effectively and cannot escape.

Containment status indicates that firefighters believe they have effectively created barriers that will stop the fire's advancement. This involves physical measures such as digging trenches, creating firebreaks, or utilizing natural features of the landscape. Understanding this is critical for incident management, as it informs fire crews and command staff of the fire's status and informs resource allocation accordingly.

Establishing control lines is a strategic decision that often occurs well before the fire is fully extinguished, focusing on prevention rather than complete eradication of the flames in the initial phases of an incident.