What must you do if you plan to break glass during an operation?

Notifying command that you will be breaking windows is essential because it ensures clear communication among all personnel involved in the operation. This action is crucial for situational awareness, as breaking glass can create hazards, such as flying debris, potential injuries, or changes in the firefighting environment. Alerting command allows for monitoring and coordination of the operation, ensuring that all team members are informed and can adjust their actions accordingly to maintain safety and effectiveness during the operation. It helps in managing the overall scene, especially in chaotic situations where multiple teams might be present.