Fire Extinguishing Systems
Fire Extinguishing Systems
A guide to their integration with other
A guide to their integration with other
building services
building services
By John Sands
By John Sands
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A joint venture with
FIRE
FIRE EXTINGUISHING SYSTEMSEXTINGUISHING SYSTEMS © BSRIA AG 17/2002 © BSRIA AG 17/2002
25/11/02
25/11/02 FIRE EXTINGUISHING SystemsFIRE EXTINGUISHING Systems
ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS
BSRIA would like to t
BSRIA would like to thank the British Fire Protection Systemshank the British Fire Protection Systems Association (BFPSA) and its
Association (BFPSA) and its members for sponsoring this publication,members for sponsoring this publication, and for providing invaluable technical guidance during its production. and for providing invaluable technical guidance during its production. Acknowledgement is also given to Faber
Acknowledgement is also given to Faber Maunsell for their assistance inMaunsell for their assistance in providing technical information.
providing technical information. Every opportunity has been taken
Every opportunity has been taken to incorporate the views of theto incorporate the views of the contributors, but final editorial control of this
contributors, but final editorial control of this document rested withdocument rested with BSRIA.
BSRIA.
BSRIA is grateful for the use of photographs and illustrations in this BSRIA is grateful for the use of photographs and illustrations in this document.
document. The use of such images doThe use of such images does not in any way imply productes not in any way imply product endorsement by BSRIA.
endorsement by BSRIA.
The BFPSA has been at
The BFPSA has been at the forefront of developments in the fire protectionthe forefront of developments in the fire protection industry since its fo
industry since its formation in 196rmation in 1966. 6. The Association The Association representsrepresents manufacture
manufacturers, installers and rs, installers and maintainers of fire alarm and fixedmaintainers of fire alarm and fixed extinguishing systems, with membership representi
extinguishing systems, with membership representing an estimated ng an estimated 95% of95% of the UK’s purchases in this imp
the UK’s purchases in this important sector of the market. ortant sector of the market. The BFPSA hasThe BFPSA has an ongoing role assisting in the development of the standards and
an ongoing role assisting in the development of the standards and
regulations which have helped to ensure that the UK has one of the best regulations which have helped to ensure that the UK has one of the best fire safety record
fire safety records in the world. s in the world. In the EuropeaIn the European arena, the BFPSAn arena, the BFPSA represents the interests of the
represents the interests of the UK fire protection industry through its UK fire protection industry through its activeactive participation in Euralar
participation in Euralarm and Eurofeu. m and Eurofeu. The Association also has a veryThe Association also has a very active training programme, offering a wide range of
active training programme, offering a wide range of courses providingcourses providing knowledge which has a real and
knowledge which has a real and practical application in the workplace.practical application in the workplace. For details of training courses by the BFPSA please turn to the end of this For details of training courses by the BFPSA please turn to the end of this document.
document.
Further details on the work of the BFPSA are available from the Further details on the work of the BFPSA are available from the secretariat: BFPSA, Neville House, 55, Eden Street,
secretariat: BFPSA, Neville House, 55, Eden Street, Kingston UponKingston Upon Thames, Surrey KT1 1BW Tel: 020 8549 5855 Fax: 020 8547 1564 Thames, Surrey KT1 1BW Tel: 020 8549 5855 Fax: 020 8547 1564 Website: www.bfpsa.org.uk
Website: www.bfpsa.org.uk
©BSRIA
©BSRIA 16511 16511 November November 2002 2002 ISBN ISBN 0 0 86022 86022 608 608 5 5 Printed Printed by by The The Chameleon Chameleon Press Press Ltd.Ltd.
All rights reserved.
All rights reserved. No part of this publication may be reproduceNo part of this publication may be reproduced, stored in a retrievald, stored in a retrieval system, or transmitted in any form
system, or transmitted in any form or by any means electronic or mechanical includingor by any means electronic or mechanical including photocopying, recording or otherwise without prior written
FIRE EXTINGUISHING SYSTEMS
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CONTENTS
1
INTRODUCTION
1
1.1 The purpose of this guide
1
1.2 The format of this guide
1
2
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2.1 General
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2.2Design
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2.3 Extinguishants
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3
STANDARDS
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4
DESIGN CONSIDERATIONS
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4.1 General
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4.2 Programming
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4.3 Procurement
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4.4 Exchange of information
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4.5 Air conditioning systems
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4.6 Ventilation systems
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4.7 Power supplies
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4.8 Controls
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4.9
Other f
ire detection and alarm systems
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4.10 Access control/security systems
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4.11 Builders work requirements
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INSTALLATION CONSIDERATIONS
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5.1 General
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5.2 Programming
33
5.3 Exchange of information
33
5.4 Site supervision
34
5.5 Air conditioning systems
34
5.6 Ventilation systems
35
5.7 Power supplies
35
5.8 Controls
35
5.9
Other f
ire detection and alarm systems
36
5.10 Access control/security systems
36
5.11 Builders work requirements
36
5.12
Operation and maintenance information
37
REFERENCES
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APPENDIX A
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APPENDIX B
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TABLES
Table 1: The number of cylinders required for different system
types for typical room volumes
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Table 2: Commonly used inert gases
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Table 3: Commonly used halocarbon agents
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Table 4: Area of pressure relief required for different system
types for typical room volumes
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Figure 1: A typical fire extinguishing system installation
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Figure 2: Discharge graph for non-liquiefied extinguishants
11
Figure 3: Discharge graph for liquiefied extinguishants
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Figure 4: Gas cylinder installation
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Figure 5: Pressure relief damper with pneumatic actuation
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INTRODUCTION
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1 INTRODUCTION 1.1 THE PURPOSE OF
THIS GUIDE
Welcome to Fire extinguishing systems – a guide to their integration with other building services. This concise document will enable building services designers to quickly familiarise themselves with the key issues of fire extinguishing systems, and how to successfully integrate them into the total services provision for a protected space or area.
The guide is also intended to be a general guide for inspectors of fire protection systems to help them to assess the quality of the installation and its functionality with the building and its systems in a systematic and clearly defined manner.
Other building professionals involved in the design and construction process, such as architects, structural engineers, and contractors – both for the building works and the mechanical and electrical services – will also find the publication useful to understand the extinguishing system and its relationship with other aspects of the building.
Fire extinguishing systems are an essential part of many contemporary buildings as they provide fast and effective control of fires in their very early stages, and before any great damage can be caused. They are particularly suitable for use in areas with high levels of electrical and electronic equipment, enabling operations to re-start quickly after discharge of the extinguishing system. This reduces down-time and disruption to a minimum, provided, of course that any fire damage is minimal.
Such systems are generally designed and installed by specialists in line with strict codes and standards. This ensures quick and effective
operation in the event of activation. However, regardless of how good the fire extinguishing system may be, to prove truly effective in
operation the system must be properly integrated with the rest of the building services systems serving the protected area. The guide will provide the basic information necessary to enable designers and the building team to provide a complete and fully integrated fire
extinguishing solution.
1.2 THE FORMAT OF THIS GUIDE
The document is organised in the following sections, which represent t he order in which the various issues would normally be addressed by the user. Fire extinguishing systems
This section contains descriptions of the main types of fire extinguishing systems currently in use throughout the UK, and the typical applications for each one. Spinklers have not been included in this document.
The systems discussed include:
• Halon • Inert gases • Halocarbon agents • Carbon dioxide • Foam • Dry powder
• Fine water spray/water mist
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Standards
The standards and guidance documents applicable to fire extinguishing systems are listed on page 19 as an easy source of reference. These standards and regulations apply to particular systems both at the design and installation stages.
Design considerations
This section examines the key aspects of the services design process and details the associated co-ordination issues. The most important factor is to ensure that the fire extinguishing system interfaces correctly with other building services systems, and the building structure and fabric.
The areas addressed include:
• Exchange of information • Air-conditioning systems • Ventilation systems • Power supplies • Controls
• Fire detection and alarm systems • Access control/security systems • Communications
• Builders work requirements
Installation considerations
This section follows on from the approach adopted in the section Design Considerations and applies them to the installation process. The best design can fall down if not properly installed.
The areas addressed here include:
• Exchange of information • Site supervision • Air-conditioning systems • Ventilation systems • Power supplies • Controls
• Fire detection and alarm systems • Access control/security systems • Communications
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Inspection checklists
The inspection checklists have been arranged to cover the complete design and installation process, and to ensure that all concerned parties are aware of what is required of them to provide a satisfactory end product.
Checklists provided include:
• A project information sheet
• A designer’s checklist (for use by the consulting engineer) • A fire extinguishing system specialist’s checklist
• A main contractor’s checklist
• Pre-commencement, interim and final inspection checklists
Fax-back response form
A fax-back form has been included in Appendix B to give the reader the opportunity to provide feedback on the publication.
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2 FIRE EXTINGUISHING SYSTEMS
This section deals with the basic principles of fire extinguishing systems, and is intended to provide the reader with a good working knowledge of the technology. Similar issues relating to the associated engineering services are addressed in Section 4.
2.1 GENERAL Basic principles
A fire extinguishing system is a type of fire protection that is used to protect a particular hazard, where more conventional forms of fire protection may not be suitable. For example, a large office block may be protected throughout the office areas and corridors by a sprinkler or pre-action sprinkler system. However, the central computer facility may be equipped with a gaseous system as a more appropriate method of fire protection.
Figure 1: A typical fire extinguishing system installation.
Although there are many different types of fire extinguishants for these systems, (as described later in this section), the basic principles of the system remain largely the same. In their most basic form, automatic detectors are located throughout the areas to be protected to sense signs of a fire. The approach of the extinguishing system is to detect a fire via a controls system and extinguish the fire before it has a chance to become established. The detectors initiate the discharge of the extinguishant into the protected space from the storage facility through pipework and
nozzles to extinguish the fire.
Inert gas systems operate by reducing the oxygen content within the protected area to a level below which there is insufficient oxygen to support combustion. The extinguishant is stored as a gas at pressures of 150-300 bar. Chemical-based systems operate by absorbing the heat and thus reducing the temperature in the protected area and, to a lesser
extent, by attacking the combustion chain. In these systems the chemical agent is stored at a lower pressure than inert gases, often with nitrogen added to create a propellant-pressure for discharge. The agent changes state to a gas upon release from the nozzle.
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System components
Such a system normally consists of the following two main elements:
• Detection, actuation and control • Extinguishant storage and distribution
Detection, actuation and control
This element of the system deals with detecting the early signs of a fire and processing the action to be taken by the rest of the system. The detection of fire is achieved by detectors located throughout each protected area, linked electrically to the control panel or unit. In a
typical computer-room application with floor and ceiling voids, detectors may be provided to give protection for each of these areas. Both optical and ionisation detectors will be used, with each area zoned to provide first and second stage operation. Coincidence operation of detection zones helps to prevent inadvertent discharges. More information on coincident operation can be found in BS 72731.
Control units should be mounted outside the protected space, and incorporate a switching facility to allow users to select the mode of operation of the system – automatic or manual. When the protected space is occupied, the system may be set to manual to avoid discharge with people in the space as described in BS ISO 14520 2. With the system switched to manual, the occupants have the opportunity to investigate the source of the fire without risk of the extinguishant
discharging. In the case of a false alarm, or a small fire that could be dealt with successfully and safely with hand-held extinguishers, this could save unnecessary discharge of extinguishant. However, in a fire emergency, such action places a special responsibility on management to remember to switch the option back to automatic or to actuate the system. The system should be set to automatic operation whenever the room is not occupied.
Extinguishant storage and distribution
The second main element of the system is the storage and distribution of the fire extinguishant. This is contained under pressure in cylinders or containers connected by pipework. A pipework network or system then runs to discharge nozzles located within each protected area or zone. The cylinders should ideally be mounted outside the protected zone to allow access for maintenance and testing without needing to gain access to the protected area itself. For large installations, the number of
cylinders required can be considerable. Space needs to be found to house them, and the area also needs to be strong enough to support their weight. However, the number of cylinders required for a particular application will vary greatly depending on the extinguishant used, with inert gas systems typically requiring more than chemical agent systems. This is demonstrated in Table 1 and gives an approximation of the
number of inert gas cylinders required for a range of room sizes, covering the three possible system storage pressures.
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Note that the figures contained here are for general guidance only, and are intended for use at the early stages of a project to help determine spatial allocation for cylinders. Average or typical size cylinders have been used, and the numbers shown can vary if other sizes are used. Cylinder quantities may also vary slightly between manufacturers. The table must not be used for detailed design purposes; the designer should discuss the exact system requirements with the fire system specialist as soon as possible in the project design process in order to determine the exact quantities that are required.
Table 1: The number of cylinders required for different system types for typical room volumes.
Room volume in cubic metres
System type 50 100 150 200 250 300 350 400 450 500 Inert gas 2 4 5 7 9 10 12 13 15 16
Chemical 1 1 1 1 1 2 2 2 2 2
CO2 2 4 5 7 9 10 12 14 15 17
Reduced storage space is a clear benefit of chemical agents and Table 1 provides a comparison based on the quantity of cylinders for inert gas, a typical chemical agent and CO2 against a range of protected volumes. However, it should be recognised that the footprint for the cylinder is not directly related to the cylinder quantity as individual inert gas and CO2 cylinders may require a smaller area than a chemical agent cylinder. Other chemical agents may have different space requirements.
Inert gases are stored in gaseous form at higher pressures than chemical agents and this allows cylinders to be located further from the protected area than an equivalent chemical agent system. For instance, cylinders for an inert gas system can be located several hundred metres away from the space being protected. This can be an advantage where space for storage is limited. By contrast, the pipework friction losses of a chemical liquefied agent during discharge means that the cylinders have to be sited close to the protected area.
The lower storage pressures used in chemical-agent systems (see section 2.3) also means that the grade of pipework and fittings required is not as great as for an inert gas system. Although cylinder storage pressures of around 200 bar are commonly used, the distribution piping is usually designed to be around 60 bar, the same as CO2. Some inert gas systems are stored at
pressures as high as 300 bar, but have the same distribution pressure of 60 bar.
The pipework used on inert gas systems consists of a high-pressure section and a low-pressure section. The high-pressure section requires pipework and fittings suitable for 100 – 300 bar system operating
pressures. The pressure is reduced at the end of its high-pressure section to 60 bar by a pressure reducer. After this point the pipework and
fittings need only be selected for a 60 bar system operating pressure. This lower operating pressure generally constitutes the majority of the
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Cylinders for use on all systems should be stored away from severe weather conditions, out of direct sunlight, and be protected from
potential damage due to mechanical, chemical or other causes. Generally the operating temperatures for total flooding systems should be in the range of –200C to +500C.
Operation
It is important that the system is arranged to operate in a manner suitable for the particular area or business being protected, within the confines of the various applicable standards.
The general method of operation involves two major stages which covers the extinguishing system itself as well as other engineering systems
serving the protected area. First stage of alarm
On automatic detection of the fire, the system should close down any air conditioning serving the protected area. Where the area is served by a central system, dampers must be installed to provide fire separation between the protected area and the rest of the ductwork system. This separation requirement also applies to any other ductwork distribution system. Any ductwork system passing through, (but not serving) the protected area shall either be fully fire rated along the section within the protected enclosure, or be fitted with fire dampers at the points of entry and exit, of the protected enclosure. In the case of stand-alone room air conditioning units, the units should be shut down. In some cases, the system may be configured to initiate a power-down procedure for computer or other sensitive equipment within the space.
Activation of the first stage alarm will allow users time to assess the
hazard and take suitable measures to fight the fire manually if appropriate, or to determine if it is a false alarm. This assessment should, of course, only be carried out by suitably trained staff. On arriving at the protected area, assuming that it is unoccupied, the users would first ascertain, as far as possible, that the alarm is genuine and therefore assess the risks that entry may pose. If the situation warrants entry, then it may be
appropriate to set the system to manual control before entering the space. This will ensure that the extinguishant cannot be discharged while
people are in the space. Some users may prefer their systems to be set to manual, while the area is occupied, so as to prevent the extinguishant from being discharged. If this is the case the users would reset the system to automatic when leaving the room. First stage alarm audible and visual alarms would be operational at this time.
An aspirating-type smoke detection system may also be employed, but is not normally linked to the fire extinguishing system.
Second stage of alarm
The second stage of alarm will be activated when smoke within a room is spreading and being detected by other devices and where the fire
extinguishing control system is set in automatic mode. In this condition activation of a second detector on another zone will activate second stage audible and visual alarms, close down any power supplies to equipment in the room via the PDU and activate the pre-discharge timer. After a
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preset period (no more than 30 seconds) for evacuation, the extinguishant would be released.
There would normally be a status signal from the detection system serving the protected area to the main building fire detection system to make the occupiers aware of the fire condition. This may be particularly useful to fire service crews on their arrival at the building.
If the extinguishing system is linked to systems such as a Building
Management System (BMS), second stage activation can be arranged to send signals to notify these other systems of the status within the
protected area. This in turn can allow the BMS to action any changes necessary and appropriate to other building services plant and systems. However, there will be many cases where the above cannot be adhered to due to the operations within the protected space. For instance, some high technology businesses such as internet hotels or bank computer centres are not prepared to risk having equipment off-line, and often go to great lengths to provide redundancy through duplicate plant and systems. In such instances, equipment within the space may be left running throughout both alarm stages. Similarly, the rise in temperature within the space that would result from the air conditioning systems being shut down would be unacceptable and so the air conditioning is left running. If such air conditioning is non-recirculating, then the system should be shut down and dampers closed on second stage of alarm. However, any system or service passing through the space will still have to be fire separated, although such areas are usually designed to avoid such an arrangement.
As mentioned earlier, the designer must give very careful thought to the operation of the space and the risks involved when deciding on an
operating strategy for the fire extinguishing system. This may involve detailed discussions with the client and the authority having jurisdiction to arrive at a suitable solution.
2.2 DESIGN This subsection deals with the general principles of designing an
extinguishing system, but only to a level sufficient to make the services designer aware of the main considerations. It is not intended that the reader of this document will be in a position to carry out detailed syst em design. A suitably qualified and accredited professional organisation or specialist must carry out the detailed design of a fire extinguishing system.
System design
The main design principles and issues associated with gaseous fire extinguishing systems are covered by BS ISO 14520-1:2000, Gaseous fire-extinguishing systems – Physical properties and system design – Part 1:
General requirements. All the information contained below is in accordance with that Standard . Parts 2 to 15 deal with particular requirements for each of the main gases available. It is also very important that, when designers consider the fire extinguishing system, they understand the type and use of the space, and the potential hazards which the system must protect against.
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Safety
The Standard referred to above details the safety measures that should be observed with total flooding systems, in both normally occupied and unoccupied areas, and the reader is advised to read and understand them in full. However, for occupied areas, these can be summarised as follows: In areas which are protected by total flooding systems and which are capable of being occupied, the following shall be provided:
a) Time delay devices
1) for applications where a discharge delay does not significantly increase the threat from fire to life or property, extinguishing systems shall incorporate a pre-discharge alarm with a time delay sufficient to allow personnel evacuation prior to discharge;
2) time delay devices shall be used only for personnel evacuation or to prepare the hazard area for discharge.
b) Automatic/manual switch, and lock-off devices where required in accordance with BS ISO 14520:2000 2, Part 1, Clause 5.2.
c) For safe use of systems in the UK, reference should be made to the HAG report 3.
Detection, actuation/operation and control systems
The detection, actuation/operation and control part of the protection system can be automatic with additional manual control, or manual operation only. The control system typically includes detecting circuits, releasing circuits (automatic and manual), interfacing circuits, alarm circuits and actuating devices, all with associated wiring.
The detection device must be suitable for early detection of fire through smoke as appropriate for the hazards present in the area being protected. To this end, it is important that both the designer and specialist
understand the use to which the space is being put so that appropriate equipment can be selected. A combination of ionisation chamber and optical-type smoke detectors should be used as ionisation-type detectors are most sensitive to flaming fires, and optical types respond best to some types of smouldering fires. The detectors should be arranged in an even pattern using equal numbers of both types of detector. Guidance is given in BS 6266 4 on the spacing of detectors required for areas containing electronic equipment, based on the floor area of the protected space, and also the number of air changes and air velocity in air conditioned areas. BS 6266 4 recommends that particular measures be adopted when dealing with electronic data processing type installations, such as reducing the area of each detector zone to give greater sensitivity, or taking into account the effects of air movement when locating detectors.
Additional fire detection can be provided by the use of aspirating-type smoke detectors. These have much greater sensitivity than either optical or ionisation detectors, and so can detect a fire at a much earlier stage. However, this high level of sensitivity brings its own problems as the systems can be susceptible to the effects of outside sources such as the quality of incoming air. If the air intake for the air conditioning or ventilation system is located near to a source of possible contamination, this may be sufficient to set off the aspirating detector. This can be addressed by adjusting the sensitivity of the system detector. These systems are usually employed for their early warning capabilities, but are not linked to the fire extinguishing system itself.
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It is a requirement of BS ISO 14520-1:2000 2 that the electrical supply to an electrically operated fire detection system is independent of the
general supply to the protected area. The Standard also states that an emergency secondary power supply must also be provided in case of failure of the primary supply (this is normally a battery).
For manual operation systems, the user control shall be located outside the protected area or, where this is not possible, adjacent to the main exit from the area. Such manual controls should also incorporate a safety device to restrict accidental discharge, or discharge during maintenance or testing.
A hold-off device can be used to suppress operation of the system, as recommended by BS 6266 4. It is normally located at the exit point from the room and requires a constant application of pressure for it to be effective.
Extinguishant concentration
The design concentration of extinguishant is related to the classification of fire to be protected against. For fire Classes A and B (as detailed in ISO 39415), BS ISO 14520-1:2000 2 states that the extinguishant concentration shall be equal to the design concentration plus a safety factor of 30%. Additional allowance may need to be made for other factors not covered by the safety factor. It goes on, however, to say that more suitable tests for use in areas with large quantities of plastics
materials, including computer rooms, are currently being developed for inclusion in the next update of the Standard . The methods for calculating the extinguishant concentration are detailed in Annexes B and C of
BS ISO 14520-1:2000 2. Discharge time
In order to extinguish the fire and restrict the formation of decomposition products due to the heat, the extinguishant must
discharge as quickly as possible. However, the discharge time is different for varying extinguishants but can be summarised as follows:
• Non-liquefied extinguishants (inert gas): The time required to
achieve 95% of the design concentration shall not exceed 60 seconds
• Liquefied extinguishants: The time required to achieve 95% of the
design concentration shall not exceed 10 seconds
However, the maximum flow rate, and hence pressure, occurs very soon after the start of the discharge as shown in Figure 2 and Figure 3 on Page 11.
Duration of protection/hold time
The appropriate extinguishant concentration needs to be achieved and then maintained for a sufficient period to ensure effective action. The period during which the concentration is maintained is known as the hold time, and is important in areas where a fire has the potential to become deep-seated, or the original cause persists, such as a faulty battery pack of an uninterruptible power supply unit. As a general rule, the hold time should be not less than 10 minutes and should be proven by
carrying out a door fan pressure test using the method described in BS ISO 14520-1:2000 2.
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With the exeption of nitrogen, extinguishants are heavier than air and, when discharged, produce a heavier-than-air mixture with the room air. As this mix leaks out, the interface formed between the mixture and the infiltrating air taking its place, descends. This is known as a descending interface. The system should be designed such that the extinguishing concentration is still achieved at the top of the highest piece of
equipment forming part of the hazard at the end of the hold time. The enclosure
In order to achieve acceptable extinguishant retention times as demonstrated by either a door-fan pressure test or full discharge test in a fire condition, it is essential that the enclosure is of tight construction. Details of the measures that need to be addressed are included in Section 4.11.
Pressure relief
With fire extinguishing agents there is a significant increase in pressure in the protected area on discharge that must be assessed and accommodated within the design if necessary. Annex E to BS ISO 14520-1:2000 2 explains the requirements of such devices in detail, and these are also discussed in Section 4.4 of this document. Pressure characteristics during discharge are shown in Figure 2 and Figure 3.
Figure 2: Discharge graph for non-liquefied extinguishants.
Figure 3: Discharge graph for liquefied extinguishants. Approximately
5seconds
Maximum time (95% of minimum design concentration) 60 seconds
Pressure
Approximately
5seconds
Maximum time (95% minimum design concentration) 10 seconds Positive pressure Negative pressure
