Under part E of Scottish technical standards (1993) version it quotes:
The intention of the requirements for means of escape is that everyone within a building may reach either a place of safety or, in certain circumstances a protected zone within 2(1/2) minutes of becoming aware of an outbreak of fire. The requirements for the number and width of exits assume a unit width of 530mm per person and a rate of discharge of 40 persons a minute. The allowable travel distance (the distance which it is assumed one can travel along an unprotected escape route within the time specified) varies according to the purpose group and situation.
However in the more up to date tech standards in Scotland (2001) amendment's, it says at the introduction to part E, "The intention of the requirements for means of escape is that everyone within a building may reach either a place of safety or, in certain circumstances, a protected zone within a reasonable travel distance. This also applies to the very latest Scottish Building Standards.
The undernoted details have been taken from the following,
Principles of Fire Safety (Fire Service College) notes,
Primary Construction
Applies to the main fabric of a building, walls, floors, roof & internal dividing walls
Buildings are categorised into 3 classes
Class A - complete non-combustible construction, i.e. elements of structure, floors, and walls. Supporting structure of brick or concrete.
Class B - traditional construction, i.e. non-combustible walls with combustible floors
Class C - combustible construction, i.e. timber floors & walls.
The times that are generally accepted are
Class A - 3 mins
Class B - 21/2 mins
Class C - 2 mins
These are not hard and fast times, and can be extended or reduced according to the particular circumstances of the case, but they do form a reasonable basis for most situations.
It seems that the most common of times quoted is 21/2 mins, and this has often been taken as a design guide. However, it’s authority rests more upon legend than fact. During a fire at the Empire Palace theatre in Edinburgh in 1911, the whole audience was reported to have been able to evacuate in the time that it took the orchestra to play "God Save the King, (21/2 mins, even though 10 people died backstage.
Other references to means of escape regarding evacuation times come from the following references.
1 - PG Wood -" A survey of Behaviour in Fires" & "Behaviour under Stress - people in fires".
2 - D Canter- "Behaviour of People, therefore fire situations "Domestic, multiple-occ & Hospital Fires”. Human Behaviour in fires & public buildings". Studies of Human Behaviour in fire - Empirical Results & their implication and for Education & Design". & "Fires & Human Behaviour
Hope some of the above is of use to you.