What does a Lockdown indicate in terms of building access?

A lockdown signifies a critical response protocol that indicates access is restricted within a building, particularly when there is a potential threat present inside the premises. During a lockdown, the primary goal is to ensure the safety of all individuals within the building by preventing entry or exit.

When a threat is identified to be inside, such as an active shooter or another type of emergency, the lockdown procedures are activated to secure all entrances, restricting access to only those who are authorized or trained to respond to emergencies. This is a preventive measure aimed at protecting occupants by controlling the environment and minimizing further risks.

In this context, the other options do not align with the nature of a lockdown. Keeping doors unlocked or allowing external visitors would compromise the safety protocols established during this heightened state of alert. The constraints placed during a lockdown are essential for safeguarding the lives of individuals within the building until the situation has been assessed and deemed safe by law enforcement or emergency personnel.