Some situations would require that all persons exit the building. This would usually be appropriate for potential fires or bomb threats.
The manager must have a plan that is known to all staff. It is usually recommended the office or department have a designated staff person responsible for assuring that all persons have safety exited the building.
In some cases, the safety person will be required to don a brightly colored vest so as to be readably identifiable and easy to locate.
If there is a bomb threat and procedures dictate that staff should leave the building, there should be a previously determined meeting place at least a block away from the building where staff can safely assemble.
The same would be true in case of fire, but the meeting place may be a different location. Evacuation routes should be posted throughout the building.