What condition must be met before the "all clear" can be given in any situation?

The condition that must be met before the "all clear" can be given is that authorities have determined there is no longer a threat to the occupants. This means that any potential hazards or dangers that prompted an emergency response have been assessed and deemed to be resolved or absent. The safety of individuals in the affected area is paramount, and without the assurance that there is no ongoing threat, it would be unsafe to declare that it is safe for individuals to return or engage normally in the environment.

While ensuring that safety protocols are followed, verifying that no further assistance is needed from emergency services, and confirming the safe evacuation of all occupants are all important aspects of the emergency response process, they do not, by themselves, determine the safety of the environment. The "all clear" declaration specifically relies on the assessment of potential threats to ensure the safety of the occupants.