Most, if not all high-rise buildings offer routes for escape in an emergency. These measures also help to prevent fire from spreading to nearby buildings, prevent premature collapse of the building and allow firefighters an opportunity to rescue people and extinguish the blaze in the quickest and safest way. However, tall buildings are more difficult to tackle when seeking to evacuate in an effective way  one that allows for mass evacuation to take place simultaneously. The use of lifts is not considered unless there are people with impaired mobility that need rescuing. As a result, the time it takes to completely clear a tall building is both augmented and fraught with danger. As buildings grow in both height and complexity, there is growing concern over safety, particularly relating to fire.