Means of Escape from Fire

Building regulations stipulate what measures must be taken to ensure that occupants of buildings can escape if there is a fire. If there are spaces in the building which have no direct access to the outside, then a route protected from fire that leads to safety must be provided. Different standards apply to different building types as follows:

(1) dwellings, including flats
(2) residential (institutional) buildings, namely those that have people sleeping in them overnight (e.g. hotels, hospitals, old people's homes)
(3) offices, shops and commercial premises
(4) places of assembly and recreation, such as cinemas, theatres, stadiums, law courts, museums and the like
(5) industrial buildings (e.g. factories and workshops)
(6) storage buildings, such as warehouses and car-parks. Special provisions must be made for escape from very tall buildings.

Factors to be taken into account when designing means of escape from buildings are:
- the activities of the users
- the form of the building
- the degree to which it is likely that a fire will occur
- the potential fire sources
- the potential for fire spread throughout the building.

There are some assumptions made in order to achieve a safe and economic design:
(1) Occupants should be able to escape safely without outside help. In certain cases this is not possible (e.g. hospitals) so special provisions need to be made.
(2) Fire normally breaks out in one part of the building.
(3) Fires are most likely to break out in the furnishings and fittings rather than in the parts of the building covered by the building regulations.

(4) Fires are least likely to break out in the structure of the building and in the circulation areas due to the restriction on the use of combustible materials.
(5) Fires are initially a local occurrence, with a restricted area exposed to the hazard. The fire hazard can then spread with time, usually along circulation spaces.
(6) Smoke and noxious gases are the greatest danger during early stages of the fire, obscuring escape routes. Smoke and fume control is therefore an important design consideration.
(7) Management has an important role in maintaining the safety of public, institutional and commercial buildings.

General Principles. The general principle applied in relation to means of escape is that it should be possible for building occupants to turn away from the fire and escape to a place of safety. This usually implies that alternative escape routes should be supplied. The first part of the route will usually be unprotected (e.g. within a room or office). Consequently, this must be of limited length, to minimise the time that occupants are exposed to the fire hazard. Even protected horizontal routes should be of limited length due to the risk of premature failure. The second part of the escape route is generally in a protected stairway designed to be noncombustible, and resistant to the ingress of flames and smoke. Once inside, the occupants can proceed without rushing directly, or via a protected corridor, to a place of safety. This is generally in the open, away from the effects of the fire.

In certain cases, escape in only one direction (a dead end) is permissible, depending on the use of the building, the risk of fire, the size and height of the building, the length of the dead end and the number of people using it.

Mechanical installations such as lifts and escalators cannot be included as means of escape from fire. Nor are temporary devices and fold-down ladders acceptable. Stairs within accommodation are normally ignored.

Due regard must be given to security arrangements so that conflicts with access and egress in an emergency are resolved.

Rules for Measurement. The rules for measurement relate to three factors: occupant capacity, travel distance and width of escape route.

Occupant capacity is calculated according to the design capacities of rooms, storeys and hence that of the total building. If the actual number of people is not known, then they can be calculated according to standard floor space factors, giving the allotted metre area per person depending on the type of accommodation.

Travel distance is calculated according to the shortest route, taking a central line between obstructions (such as along gangways between seating) and down stairs.

Width is calculated according to the narrowest section of the escape route, usually the doorways but could be other fixed obstructions.

Means of Escape from Dwellings. The complexity of escape provisions increases with the height of the building and the number of storeys above and below the ground. Flowever, there are recommendations that refer to all dwellings:

Smoke alarms. These should be of approved design and manufacture and installed in circulation areas near to potential sources of fire (e.g. kitchens and living rooms) and close to bedroom doors. Installation should be in accordance with the details of the manufacturer and the building regulations. The number of alarms depends on the size and complexity of the building, but at least one alarm should be installed in each storey of the dwelling, and several interlinked alarms may be needed in long corridors >15m). Consideration must be given to ensure the easy maintenance and cleaning of the alarms.

Inner rooms. Escape from these might be particularly hazardous if the fire is in the room used for access. Inner rooms should therefore be restricted for use as kitchens or utility rooms, dressing rooms, showers or bathrooms, unless there is a suitable escape window at basement, ground or first floor levels.

Basements. Gases and smoke at the top of internal stairs makes escape from basements hazardous. Therefore basement bedrooms and inner rooms should have an alternate means of escape via a suitable external door or window. Regulations stipulate detailed dimensions for windows and doors used for escape purposes.