Section 2. Principles of Fire Safety

2.1 General

Fire safety has the primary objectives of preventing from occurring,
controlling any fire that may occur
and minimising its effect on the life safety of people in or around the building on fire.

A complete fire safety package needs to incorporate 'fire prevention' measures designed to prevent a fire from starting, and 'fire protection' measures designed to protect people, buildings and contents from the effects of a fire should it occur.

There is a mandatory requirement to protect people from injury and death in the event of a fire, but this must be seen as the minimum requirement in any fire safety strategy, as damage to buildings or stock, which are not covered by regulations, can have serious implications on a company and its ability to trade as well as involving them in direct financial losses.

For this reason the regulatory requirements must be considered as the starting point in the provision of fire safety measures. There is also a need to protect fire fighters during any search and rescue operation.

Therefore, whilst the primary objective of a fire safety strategy should be to prevent a fire from starting, there is a secondary objective of limiting its growth and mitigating the damage that it may cause to the fabric and contents.

2.2 Fire Prevention

In order to prevent fires from occurring it is important that all fire hazards are identified. One of the objectives of this guide is to help identify those processes and situations that may cause a fire as well as the risk of them doing so.

Processes or equipment which generate heat are potentially major causes of fire and good fire prevention measures should ensure that these heat sources do not come into contact with combustibles that may ignite as a result of the heat.

Once the hazard has been identified, it is necessary to implement the measures needed to reduce the risk by instigating the required good practices, preventative maintenance and the correct management procedures.

These have been identified appropriately in this document.

2.3 Fire Protection

Fire protection measures are designed to come into play to reduce the impact that a fire will have, should it occur. There are two aspects to fire protection, generally known as active fire protection and passive fire protection.

2.3.1 Active Fire Protection Measures

Active fire protection covers fire detection, fire alarms and if appropriate, fire suppression together with the possible use of smoke control, pressurisation, ventilation, etc.

Fire detection and fire alarms do not in themselves do anything to control the fire or limit fire spread. A by-product of rapid detection is that it enables first aid fire fighting to be brought into play early in the fire scenario, so that the fire brigades can be summoned either automatically or manually soon after the fire has started.

Alarms make everybody in the vicinity of the area under threat aware of the fire occurrence so that they may take the necessary actions to ensure their safety. Alarms therefore have a major role in providing life safety, and restricting damage, but do not themselves counter the development of the fire.

Fire suppression measures come in several forms. In the case of process plant such as fryer or ovens, these will often have built-in suppression systems such as CO2 or steam drenchers. In the case of large buildings, sprinklers or water curtains may be used.

There are special factors in considering whether or not to use sprinklers at very low temperatures, e.g.. in cold stores, and these points are discussed in Paragraph 3.6. Nevertheless sprinklers may be appropriate for use in ambient or chilled areas, subject to there being no conflict with other requirements such as hygiene. Fire suppression equipment plays a major role in preventing a small fire from becoming a large fire.

Smoke control can do much to limit the damage done by hot smoke both by its removal or temperature reduction as a consequence of ventilation. Spread of smoke can be controlled by the use of pressurisation measures in areas adjacent to the fire.

2.3.2 Passive Fire Protection Measures

Passive fire protection takes a number of forms. The structural elements must not collapse within a period during which the life safety of the occupants including fire fighters, could be put at risk.

The linings, except for those linings to small rooms, need to be controlled in order to reduce the spread of fire on the face of linings and to reduce the rate of fire growth. Some of the walls, and floors or ceilings are required by regulations to resist fire for a pre-determined duration, either to form protected routes to aid the egress of personnel, or to separate higher risks or to limit the size of compartments.

Normally the occupants, particularly at ground level, will be expected to evacuate a building before conditions become life threatening. This is mainly achieved by planning the layout so that they have only relatively short distances to travel to an exit.

However, where the distance is longer than normal then the route should lead to a place of comparative safety, and be protected by a fire resisting construction which allows unhindered egress to the outside of the building. In the case of persons on upper floors, stairways are frequently required to be enclosed in fire resisting constructions, unless suitable external routes are available.

The recommendations to limit the size of the compartment by means of fire resisting construction are designed to restrict the extent of a fire, and possibly to make it more manageable to fire fighting or, in the case of insurance requirements, to limit the loss of both the building and stock or equipment.

Recommended restrictions on compartment size will be given in the appropriate regulations or insurance guides. Where processes are more prone to fire, or where the equipment or process is critical or of special value, then such areas will be bounded by fire resisting constructions.

Even where fire resisting construction has been used, there have been a number of cases where fire has spread rapidly through concealed cavities (such as suspended ceiling voids), or has penetrated otherwise fire resisting construction by exploiting gaps left around services penetrating the elements. Cavities, which could cause serious fire spread, need to be sub-divided with fire resisting cavity barriers, designed to restrict fire spread and capable of withstanding the anticipated deflection in the elements around them.

All openings around service penetration through fire resisting constructions should be sealed by sealing systems that are able to maintain the fire resistance of the elements and, where appropriate, protect the core of the panel. As smoke is a major threat to life safety and a major component of fire damage, the smoke tightness of the construction needs to be considered.

2.4 Means of Escape

As identified above, the layout of the building needs to provide for easy evacuation of the occupants in the event of an emergency. This guide is primarily concerned with the fire safety management of the premises rather than the design of the building, and so the designer, who needs to know more about the provision of adequate means of the escape, should refer to the appropriate national Building Regulations and associated guidance.