Smoke spread is the most common cause of death or injury in a fire situation. In fact it is much more likely to cause harm than the fire itself. As such it is required of most fire doors, particularly those designed to preserve an escape route, to provide a degree of smoke control as well as preventing the fire from spreading.
Fire doors are a vital component of the fire safety order (2005) witch came into effect in October 2006. Their main uses are to protect the escape routes in the event of a fire and to provide a degree of compartmentalisation to stop the fire from spreading.
There have been many cases where a person has fallen unconscious whilst trying to escape a building and an automatic fire door has provided the fire brigade with enough time to rescue the person before the fire or smoke spreads. Without fire doors a fire will spread much more quickly around your building and put people lives in danger.