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Types of Fire precautions, their use as Compensation Features
Fire precautions are often categorised into two groups, active and passive. A fire safety design will rarely rely on only one or the other categories, usually a combination of fire precautions will be necessary to achieve a safe design.
Active Fire Precautions:
Active fire precautions are those installations that usually monitor for the presence of a fire or smoke /or interact with a fire when it occurs. The most common example of active fire precautions is AFD (Automatic Fire Detection). This installation is constantly reviewing the condition in the building and effectively reporting back a 'no fire' / 'fire' condition. Similarly, suppression systems, such as sprinklers, monitor the conditions, should a fire occur, the extinguishing media will be used to control / extinguish the fire.
Passive Fire Precautions:
In contrast to active systems, passive fire precautions, typically lie dormant until a fire starts and then they stay in that condition. A common example of a passive fire precaution is compartmentation, i.e. fire walls. A wall is constructed using appropriate materials, with part of its purpose to prevent fire spread from one area to another, usually for a specified time. The wall does not act or monitor the fire condition and does not normally change during the fire condition.
The examples above a very simplistic. For example there are some precautions that act in a passive manner until they are heated, then their properties alter to achieve the desired objective.
Which precautions to choose?
As previously discussed, it is unlikely that a safe design will be achieved via one category of precautions, for example a building fully compartmentalised is unlikely to be safe without any automatic fire detection and vice versa.
There is rarely a clear cut right or wrong answer in terms of what precautions to adopt, however, as with most projects, costs will be an important factor. It may be possible to specify systems that achieve life safety compliance based on an optimal cost basis. However, pure costing is often more complicated, with some precautions, such as a fire wall only really attracting a 'capital cost', whereby once the precaution is built, it will require little in terms of maintenance / testing and is unlikely to require updating or modification. However, active systems, by virtue of their very nature will require testing, servicing and maintenance and are likely to have a lifespan in which time they may need to be replaced.
Code Compliance / Compensation Features:
Understanding the types of fire precautions available will enable alterations to be made to code compliant solutions. For example, should fire compartmentation (passive precautions) be required by codes of practice, but deemed prohibitive to the design, active precautions could be offered as a compensation feature. Compartmentation is usually required to protect escape routes, thus reducing the time occupants spend in a potentially dangerous environment. The use of comprehensive AFD, ensuring that occupants receive early warning of a fire, will also ensure persons spend a reduced time in the same environment. This example highlights that two very different fire precautions can achieve the same goal.
It is noted that the example provided is again, very simplistic, it is the understanding of the approach to selecting fire precautions that is important. Fire Engineers must ensure they understand the functional objectives of the code, which form the benchmark for life safety. This coupled with the project objectives will ensure that the fire safety installations compliment the design rather that suppress it.
We very much look forward to hearing from you and helping you select the optimal fire safety measures for your individual needs.
If you would like to know more – or would like to arrange an appointment with one of our senior fire safety advisers – simply call Peter Gyere on 020 8668 8663.