Focus

Focus Archive

Evacuation drill

October 2001
Sheila Pantry, OBE

The tragic events of 11 September 2001 in the USA are re focusing attention to the speedy evacuation of people from buildings. Attention to details such as building design, criteria for means of escape, alternative means of escape, ensuring people of all abilities are able to evacuate with equal ease.

During European Week for Safety and Health an emergency exercise involving the mass evacuation of several London theatres will take place. The Ambassador Theatre Group, which owns nine West End theatres in London is planning to ask patrons and employees to carry out times evacuations after each performance during the week.

Criteria for Means of Escape

The basic principles for the design of means of escape are:

  1. there should be alternative means of escape wherever possible;
  2. where direct escape to a place of safety is not possible, the means of escape should consist of two parts –
    • an unprotected escape route which should be limited in extent and should lead to a protected escape route, and
    • the protected escape route which should lead to a place of safety.

The ultimate place of safety is, of course, the open air clear of the effects of the fire. In modern large and complex buildings, however, reasonable safety may be reached within the building, provided planning and protection measures are incorporated.

The following are not acceptable as a means of escape:

  1. lifts (except a lift which is suitably designed, and installed for the purpose of evacuation);
  2. passenger conveyors or escalators;
  3. portable ladders and throw-out ladders;
  4. manipulative apparatus and appliances.

Alternative Means of Escape

There is always the possibility of the path of a single escape route being rendered impassable by fire or a concentration of heavy smoke or fumes and, ideally, people should be able to turn their backs on a fire wherever it occurs and travel away from it to a protected escape route leading to a place of safety. When account is taken, however, of the way the building is to be used, there are many circumstances in which it is not reasonably possible to provide alternative means of escape from all parts of the floor or building. In limited conditions a dead-end can be accepted as providing reasonable safety. These conditions depend on the use of the building and its inherent fire risk, the size and height of the building and the numbers of persons accommodated within the dead-end.

Unprotected and Protected Escape Routes

The unprotected part of an escape route is that part which a person has to traverse before reaching either the safety of a final exit or the comparative safety of a protected escape route. Unprotected escape routes, therefore, should be limited in extent so that people do not have to travel excessive distances exposed to the immediate danger of fire and smoke. Even with protected horizontal escape routes the distance to a final exit or protected stairway needs to be limited because protection is not given indefinitely and the possibility of premature failure exists.

Protected stairways are designed to provide virtually “fire sterile” areas which lead to places of safety outside the building. Once inside a protected stairway, a person can be considered to be safe from immediate danger from flame and smoke and can then proceed to a place of safety at his or her own pace. To enable this to be done, flames, smoke and other products of combustion must be excluded from these escape routes (as far as is possible) by fire and smoke resisting structures or by an appropriate smoke control system, or a combination of both these methods. This does not preclude the use of unprotected stairways for day-to-day circulation, but these “accommodation” stairways can only play a very limited role in with a disability in the event of an emergency.

Guidance and advice is available in a number of publications and references from authoritative organisations are included some of the Health and Safety Publishing portfolio of products - FIRE-CD, Fire Worldwide, OSH-ROM, OSH Plus, OSH Online and OSH-Ireland.