You must know what to do if an alarm sounds. It can save your own life, and the life of others!
Simply:
Floor wardens will normally wear safety helmets or will be Security Officers in uniform. These staff members will advise you when it is safe to re-enter the building.
You need to be aware of the emergency procedures for your workplace, whether it is an office, study, laboratory or lecture theatre. For more information, study the emergency map at the entrance to the building in which you work. You must be aware of the emergency exits, the evacuation assembly area, and have read the emergency procedures. Ask your supervisor if you have any questions in relation to these.