Home Qualifications
Home
Qualifications
 

Contents

Section 1 Introduction

Section 2 Fire Extinguishing Systems

Section 3 Fire Alarms

Section 4 Smoke Extraction
                                             


 

Description:  The purpose of this unit is to enable you produce and evaluate detailed designs for firefighting and fire suppression/protection installations.

Author:  Gates MacBain Associates


Section 1  Introduction



Aims and Objectives

At the end of this section you should be able to:
  • Understand the difference between an active and passive fire fighting system.


Fire fighting systems are referred to as active systems, examples of these are water sprinkler and spray systems while the measures used to protect materials are known as passive which will generally consists of a coating of fire resistant insulating material applied to the structure. In this unit we will look just at the active systems though explanations of the passive, as well as the active, can be found on the HSE website linked to below.
 
A good source of information relating to the installation and maintenance of fire setection systems can be found in the Red Book, this can be accessed on line from the web link below or downloaded from the site. 
 


Websites


Self-Assessment Task

  • Explain and give examples of active and passive fire fighting systems.




Section 2  Fire Extinguishing Systems


Aims and Objectives

At the end of this section you should be able to:
  • Explain the types of systems used for fire protection in a building.


Portable
 
Portable firefight equipment relates to fire extinguishers and fire blankets as they can be carried easily to the scene of a fire to provide a measure for immediate first action.  The website link below provides information relating portable equipment.

 
Fixed Fire Fighting Installations

These are fire-fighting systems which are normally installed within the structure of the building. They include:


Hose Reels 

Permanent hose reels are installed in accordance with BS EN 671-3: 2000 and provide an effective fire-fighting facility. They may offer an alternative, or be in addition to, portable fire-fighting equipment.
 

Sprinkler Systems 

Sprinkler systems designed to protect life and/or property and may be regarded as a cost-effective solution for reducing the risks created by fire as they can be very effective in controlling fires.  A sprinkler system is usually part of a package of fire precautions in a building and may form an integral part of the fire strategy for the building. 

Sprinkler protection could give additional benefits, such as a reduction in the amount of portable fire-fighting equipment necessary, and the relaxation of restrictions in the design of buildings. Guidance on the design and installation of new sprinkler systems and the maintenance are provided by BS EN 12845 or BS 5306-2. 
 
Guidance is available from the Fire Safety Advice Centre on domestic and industrial fire sprinkler system, which can be accessed from the links below.
 
 
Wet and Dry Risers
 
Wet and Dry risers are intended for the use of the Fire Service to provide a readily available means of delivering considerable quantities of water.
 
Dry risers are vertical mains fitted into staircase enclosures or other suitable positions, constructed of 4'' galvanized steel pipe with outlet valves on each floor and an inlet  fitted at ground level to enable the fire brigade to connect to the water supply.
 
Wet risers are pipes kept permanently charged with water either from a storage tank (via a booster pump) or direct from the town's main water supply.
 
Details of these systems can be found by selecting the website link below.
 
 
Foam Inlets
 
Foam inlets are special inlets usually fitted to provide an efficient way of extinguishing a fire in a basement or other area of high risk such as plant room. In many respects they look the same as rising main inlet boxes, but the door should be clearly marked "foam inlet". The risk area should be kept clear of obstructions to allow the foam to spread into the compartment.
 
 
Sprinkler Systems
 
This is a system containing pipe-work which can be filled with water (wet system) with a sprinkler which seals the pipe-work.  If the temperature reaches a certain level the glass breaks and release water in the area of the fire. An alternative system is where the pipe-work is not filled with water until the sprinkler bulb is broken which then lets water into the system. Further details can be found on the Residential Sprinkler Associate website below.
 
 
 Article
 
Dry Risers Explained

A dry riser is an important component in the fire suppression system for buildings that have multiple levels. It is a type of pipe, and it is called a dry riser because during normal conditions it does not contain any water. It differs from a wet riser in that those already contain water. The purpose of the dry riser is to provide water to hose pipes that can then be used by firemen. It is also sometimes referred to as a standpipe.

A fire can happen anywhere in a multilevel building, and this can cause real headaches when it comes to putting the flames out. It would not be practical for firemen to run hoses from the ground floor all the way up to the 20th floor or above, so another option is required. This is where the dry riser comes into play. It provides a pipe to all the floors that will be contained within a fire resistant shaft. This makes it possible to get water quickly to wherever it is needed.

The difference between dry risers and wet risers is that the former already contains water and the later does not. The water inside the wet riser needs to be constantly pressurised and so it is connected to a pump it also needs to be connected to a storage tank full of water. The main reason for choosing a dry riser over a wet riser is that in some cases there may be a risk that the water inside the pipe could freeze. The fact that the dry riser is kept empty of water means that this cannot happen. The pipe is still kept pressurised but instead of water it uses air for this. It is relatively easy for the firemen to attach the dry riser to a water supply when this is required for fighting fire. The connection for this will usually be on the ground floor. It is also common for the dry risers to be connected to the sprinkler system.
 

Legal Requirement for Dry Risers

Dry risers are not only installed into buildings because they are such a good idea, but there is also a legal obligation to install them. Any floor that is 18 meters above the ground will be expected to have a dry riser access point. This is to ensure the safety of those who use the buildings and the safety of those who will have to fight any fire. It is also the obligation of those who are responsible for these buildings to ensure that regular testing occurs to ensure that the dry riser is working. It is far too late to discover during the middle of a fire that there are some problems with the system. Most of the firms that provide the equipment for this system will usually also provide testing.

Dry risers play an important role in keeping people safe inside high rise buildings. This is something that most people will just take for granted, but it is hard to imagine how fire fighters cut put out fires without this technology.


Provided by Nationwidedryrisers.co.uk




Websites


Publications

  • Hall, F & Greeno, R, (2009) Building Services Handbook; Oxford: Elsevier (Chapter 13)
  • Chadderton, D, (2007) Building Services Engineering; Abingdon: Taylor & Francis (Chapter15)


Self-Assessment Task

  • Discuss the types of systems that are available to provide fire protection in a building.





Section 3  Fire Alarms


Aims and Objectives

At the end of this section you should be able to:
  • Assess the systems of Fire alarms available.


The purpose of a Fire Alarm Systems is to warn people in a building that there may be a fire and that the building should be evacuated. They tend to operate by a detector detecting smoke or heat, or someone operating a break glass unit.  It may also incorporate remote signalling equipment which would alert the fire brigade via a central station.
 
Fire Alarm Systems can be broken down into three categories, Conventional, Addressable Analogue Addressable and Wireless systems. Information on these systems can be gained by visiting the Fire Safety Advice Centre page for Fire Alarms below.
 


Websites


Publications

  • Hall, F & Greeno, R, (2009) Building Services Handbook; Oxford: Elsevier (Chapter 13)
  • Chadderton, D, (2007) Building Services Engineering; Abingdon: Taylor & Francis (Chapter 15)


Self-Assessment Task

  • Discuss the types of Fire Alarms which would be suitable for use in a commercial environment.





Section 4  Smoke Extraction



Aims and Objectives

At the end of this section you should be able to:
  • Explain how smoke behaves in the event of a fire in a building and suggest ways that can be utilized to reduce its effects on users.
 


We learnt previously that the severity of a fire is dependent on the amount of fuel and oxygen.    I large open buildings the amount of available oxygen is likely to be considerable which means that it will be difficult to suffocate the fire by cutting off the oxygen supply or sealing off the fire.    Any smoke produced can spread both vertically and laterally at speeds of up to 5m/s. As warm air rises the smoke will rise within the enclose space which will start a build-up of smoke.  The movement of smoke can prevent a danger in itself as it can drive people into the fire as shown in the illustration of a shopping mall below. The rate at which the space becomes filled with smoke will depend on the materials being burnt and the geometry of the building. Smoke contains toxic substances which can asphyxiate and disorientate people within seconds and can kill them in minutes.                                                                                    

        
Figure 4.1 Fire in a Shopping Mall
 


Smoke Control Design Principles
 
The principle of smoke control is to limit the spread of smoke through the building and provide a means which extracts the smoke and heat from the building. This is done by providing:
 
Openings or fans at high level to ensure that the smoke and hot gases are removed from the building.

Barriers to restrict the spread of smoke through the building.  This prevents smoke travelling the length of a building making it difficult to know where the fire is which can cause people to run towards the fire.  The use of barriers can restrict the flow of the smoke maintaining a clear indication of where the fire is situated.  This can be seen in the illustrations of a fire in a shopping mall below with the barriers.

Inlet ventilators to provide a replacement air supply to balance the smoke being extracted. Ventilator controls can be linked directly to the main smoke detection system or may be dual purpose so that they can also be used for normal ventilation.  
 


Figure 4.2 Shopping Mall with Barriers
 

Details of a smoke extraction system can be found by visiting the website listed below. There are also many useful websites of manufacturers of smoke control equipment such as SE Controls.  This provides details of the principles, requirements, regulations, products and includes case studies: Though an excellent document is produced by Colt International which provides a good understanding of the subject.
 


Websites


Self-Assessment Task

  • Suggest measures that can be utilized to reduce the danger of smoke in a shopping mall.





Site Map