Fire Suppression design

Designing the fire detection, for a fire suppression system is similar to what would be required for a standard building fire alarm system.
When designing a fire suppression system, the type of detector to use used is as follows:
The selection of detectors of the fire alarm panel should be in accordance with the recommendations given in BS 5839-1 and, where applicable, BS 6266.
In some circumstances, fire detection considerations might dictate the
need for use of two different principles of detection (e.g. optical smoke
detectors and ionization chamber smoke detectors) to ensure the
earliest warning of fire and give the fire suppression system the maximum amount of time to extinguish the fire. In such circumstances, an even distribution of each type of detector should be provided throughout the protected
space. Where coincidence is used, normally it should be possible to
achieve coincidence from two detectors of the same operating
principle. In these cases, if, for example, two independent circuits are
used to achieve coincidence, there should normally be an approximately equal number of detectors of each principle connected to each of the independent circuits. For example, where four detectors are required to protect the space and these comprise two optical smoke detectors and two ionization chamber smoke detectors, there should be one optical smoke detector and one ionization chamber smoke detector on each circuit.
However, it is not always necessary to use two different principles of
fire detection. For example, given the type of fire anticipated and the
speed of detection required, it might be acceptable to use detectors of a single type.
See a video of a Fire suppression system in action.

Fire alarm design - Zones

Fire alarm design should take into account the recommendations applicable to fire detection zones that contain non-addressable automatic fire detectors. The following recommendations are applicable.
a) The floor area of a single fire alarm zone should not exceed 2 000 m2.
b) The search distance (the distance that has to be travelled by anyone responding to a fire alarm signal after entry to the zone in order for the location of the fire to be determined visually,should not
exceed 60 m.
Having entered the zone, the person responding to the alarm signal need not reach the seat of the fire within the recommended search distance; it is only necessary to become aware of the location of the fire.
In measuring search distance, the worst case, in which the fire is located at the furthest concealed area from any likely
point of entry to the zone, should be considered.
Automatic fire detectors within any enclosed stairwell, liftwell or other enclosed flue-like structure should be considered as a separate detection zone. Manual call points located at final exits to open air
from stairwells may be incorporated within these detection zones ,but may alternatively, be incorporated within the detection zone.

Fire Alarm Zones

In many buildings, the evacuation strategy will be very simple; on operation of any fire alarm manual call point, or detection of fire by  automatic fire detection, fire alarm sounders will operate throughout the building to indicate the need for evacuation of the entire building.
In larger, more complex buildings, the fire “Evacuate” signal may, in the first instance, be restricted in extent (e.g. to a single floor, a limited number of floors or a limited area of the building). In other areas, an fire “Alert” signal may be given to warn occupants of the fire alarm signal, without any requirement for those occupants to
evacuate.

In order to support such arrangements, it is necessary for the building to be divided into a number of individual alarm zones and for the installation of an addressable fire alarm system.  The operating state of fire alarm sounders in any alarm zone is independent of the operating state of fire alarm sounders in all other alarm zones. The fire alarm sounders control by the addressable fire alarm are thus grouped, so that, at any point in time, all alarm sounders within any given alarm
zone are in the same state (i.e. silent, giving an “Alert” signal or giving an “Evacuate” signal).
The need for sub-division of a building into discrete alarm zones may arise for a number of reasons,
including:
1.the use of phased evacuation.
2. to avoid unnecessary disruption when false alarms occur.
Any other circumstances in which a two stage alarm arrangement applies.
Since it will be the case that, when occupants of one alarm zone are required to evacuate, occupants of one or more alarm zones above, below or adjacent to that zone will be expected to remain in the building, every alarm zone needs to be separated from all other alarm zones by fire resisting construction. (In some complex
public buildings, such as shopping centres, alarm zones are designed to coincide with smoke control zones,
which are separated from each other by smoke curtains, rather than fire resisting construction. However, in this case, the audible signal is normally given by a voice message, rather than audible fire alarm devices.)
As the sub-division of a building into alarm zones implies that, in the early stages of a fire, occupants in
certain areas will not be expected to evacuate, the configuration of alarm zones might require approval by
the authority responsible for the enforcement of fire safety legislation in the building.

Fire alarm control panel – Fire Systems Ltd

Below is information for convention fire alarm panels used by Fire Systems Ltd.
Detection zone wiring
The detection zones from our convention fire alarm panel, provide a nominal 24V DC to power the conventional fire detection. The fire alarm wiring is monitored for open and short circuit fault conditions by removing the 6K8 end of line monitoring resistors that are supplied fitted to the fire alarm control panels’ terminals and placing them across the last device that is wired to the zone circuit.
Fire detection zone circuits must be wired as a single, radial circuit with no spurs or T junctions to enable the monitoring circuit to work correctly.
On T series fire alarm panels, polarised sounders must also be wired across the detection zone but in reverse polarity to that shown by the zone terminals. At least one sounder should be fitted to each fire detection zone. Each zone can be configured individually as a 2-wire type zone or a non 2-wire type zone using configuration options C1 to C8.
For non 2-wire fire alarm system that are required to comply with BS5839 Part 1: 2002 detector removal requirements, detector bases fitted with a Schottky diode should be used and the end of line resistor replaced with an LCMU active end of line monitoring device.

Radio linked fire alarm systems

Some of the recommendations, applicable to wired fire alarm systems, are unsuitable for, or cannot be applied to, radio fire alarm systems. These include, in particular, those relating to power supplies and fault monitoring.
Additional recommendations apply to radio-linked fire systems in order to address the integrity and performance of the radio communications link between components and the fire alarm control and indicating equipment.
In practice, no fire systems can have total reliability, but one of the objectives of good fire system design is to reduce the probability of the fire alarm system being inoperative in the area of a fire when the fire starts. It is useful that the advantages and disadvantages between the two technologies, hardwired and wireless fire alarms and radio linked systems, are different because this allows for a system to be installed that suits the site. Great care needs to be taken when assessing a site and choosing the technology to use, as neither the wireless fire alarm nor hardwired system is singularly suitable
for every site.
Components of a fire system interconnected by radio-links may include fire alarm devices, such as fire alarm
sounders, as well as detectors and manual call points. However, exercising the fire system with testing and evacuation drills in excess of those recommended by the manufacturer can reduce the life of the radio-linked fire alarm sounder batteries. Automatic silencing of radio-linked sounders on wireless fire alarm systems, is sometimes employed to overcome the potential for undue discharge of sounder batteries. However, sounders with this facility need to reactivate with any new fire or phased evacuation command. Such a facility ought not to impair the system’s ability to provide an adequate audible warning to the occupants of the building in the event of fire.
Other components of a radio fire alarm system may include radio relay units, which are installed remote from
the control and indicating equipment so as to extend the range of the system. Where such relay units are separate control and indicating panels, this is a form of networked system .
Radio communications may also be used to link a small number of detectors and other components to what is essentially a wired system. The recommendations of this standard apply equally to integral radio-linked systems of this nature.

Wireless fire alarm systems

Radio fire alarms, or also refer to as wireless fire alarms are becoming more popular as the technology improves.
A Radio fire alarm/Wireless fire alarm should comply with all recommendations BS EN 54-25.
In accordance with BS5839-1, clause 27 All fire alarm radio-linked components should be supplied from at least two independent power supplies. These can be either:
i) the normal mains supply plus a reserve battery (primary or continuously charged secondary); or
ii) a primary battery plus a second primary battery; or
iii) a primary battery plus a secondary battery.
Components, other than fire alarm control and indicating equipment, may utilize batteries to provide the normal power supply;
Wireless fire alarm/Radio fire alarm, that use power supplies incorporating one or more primary batteries should give 30 days warning of impending battery failure". This should be indicated as a low battery warning condition at the control and indicating equipment;
At the point at which the power supply(ies) to any radio-linked component can maintain the component in normal operation for no more than seven days, and, in addition, in the case of fire alarm
devices, 30 min in the alarm condition, a fault warning should be given at the control and indicating equipment;

Fire alarm spacing and siting of fire detectors

When designing a fire alarm, the heat and smoke detectors installed, depend on convection to transport hot gases and smoke from the fire to the detector.
When designing fire alarms, spacing and siting of these detectors needs to be based on the need to restrict the time taken for this
movement and to ensure that the products of combustion reach the fire detection in adequate concentration. In a building, the hottest gas and the greatest concentration of smoke will generally form at the highest parts of the enclosed areas, and it is here, therefore, that the fire detection need to be sited.
As the smoke and hot gases from a fire rise, they become diluted with clean, cool air, which is drawn into the plume. Hence, the size of fire required in order to operate heat or smoke detectors increases rapidly as the height of the ceiling above the fire increases. To some extent, this effect can be countered by the use of more sensitive detectors.
fire alarm system, incorporating optical beam detectors are less sensitive to the effects of ceiling height than are point-type detectors, since the increased size of plume will involve a greater proportion of the path length of the optical beam and help to alleviate the effects of reduced smoke density. In addition, the entrainment of air cools the gases. If the ceiling is high and the ambient temperature in the
uppermost areas within the protected space is high, the plume of smoke and hot gases may reach ambient temperature before reaching the ceiling. If the temperature of the surrounding air increases with height, (e.g. as a result of solar gain), it is possible for the air at the uppermost levels to be at a higher temperature than that of the plume. The plume will then spread out to form a smoke layer before it reaches the ceiling, as though there were an “invisible ceiling” at a specific height within the protected space. This is known as
stratification, and, at this stage of the fire growth, the smoke and hot gases will not operate ceiling mounted detectors, regardless of their sensitivity.

Fire alarm manual call points

Fire alarm manual call points need to be prominently sited, readily distinguishable from non-fire alarm call points and need to be distributed such that, from any point in the building, it is impossible to leave the storey or the building without passing a fire alarm manual call point.
When designing a fire alarm system, sufficient call points need to be provided to minimize, to a reasonable extent, the delay between discovery of a fire and the sounding of the fire alarm system. Where the fire hazard level is high and rapid fire development is
anticipated, this delay needs to be commensurately shorter.
Manual call points can, if present in unsupervised areas, be subject to malicious operation. For this reason,they are not normally provided in, for example, public common areas of shopping complexes and certain
public houses. In public car parks within a building, use of an emergency voice communication system could be considered instead of manual call points.

Fire alarm installation practices and workmanship

The nature and quality of the fire alarm installation work needs to be such as to maintain the integrity of the fire alarm system and minimize the duration and extent of disablement of the system during maintenance or modifications. Installation practices and workmanship need to conform to the requirements of BS 7671.
Penetration of construction (e.g. for the passage of cables, conduit, trunking or tray) need to be “fire stopped” to avoid the free passage of fire or smoke, regardless of whether the construction has a recognized degree of fire resistance.
Recommendations:
The following recommendations are applicable.
1) The entire electrical fire alarm system installation should conform to the requirements of BS 7671. In general, the recommendations of this standard supplement, but do not conflict with, these requirements. Where any such conflict is considered to exist, the recommendations of this standard should take precedence.
2) Cables which are directly fixed to surfaces should be neatly run and securely fixed at suitable intervals, in accordance with the recommendations of the cable manufacturer. Cables should not rely on suspended ceilings for their support.
3) The installer should ensure that all wiring complies with, at least, 26.2f) to 26.2o).
d) Joints in fire alarm cables, other than those contained within the enclosures of equipment, should be avoided
wherever practicable [see 26.2g)].
4) So far as is reasonably practicable, cable routes should be selected to follow the recommendations .
Care should be taken to ensure the electrical continuity of electromagnetic screens, including metallic
sheaths of cables.
5) Where new conduit, trunking or tray is installed, its capacity should be in accordance with the
recommendations given in BS 7671.
6) Where a cable passes through an external wall, it should be contained in a smooth-bore sleeve of metal
or other non-hygroscopic material sealed into the wall. This sleeve should slope downwards towards the outside and should be plugged with a suitable non-hardening waterproof compound to prevent the entry of rain, dust or vermin.
7) Where a fire alarm cable passes through an internal wall, a small clearance hole should be provided. If additional mechanical protection is necessary, a smooth-bore sleeve should be sealed into the wall.
8) Care should be taken to ensure that the ends of any sleeves are free from sharp edges which might
damage cables during installation.
9) When a cable passes through a floor, the considerations a
sleeve should extend as far above floor level as is required for protection of the cable it is to carry, but never less than 300 mm.
10) Where cables, conduits, trunking or tray pass through floors, walls, partitions or ceilings, the surrounding hole should be as small as reasonably practicable and made good with fire stopping
materials that ensure that the fire resistance of the construction is not materially reduced. Spaces through which fire or smoke could spread should not be left around the cable, conduit, trunking or tray.
11) If cables or conduits are installed in channels, ducts, trunking or shafts that pass through floors, walls, partitions or ceilings, barriers with the appropriate level of fire resistance should be provided
within the channels, etc. to prevent the spread of fire unless, in the case of ducts and shafts, the construction of the duct or shaft affords equivalent fire resistance to the structure penetrated; in the
latter case fire stopping need only be provided where cables pass into, or out of, the duct or shaft.

Grade of fire alarm system

Fire alarm System Grades relates to the engineering aspects of the fire detection and fire alarm system. Higher Grades of fire system design, tend to provide a greater level of control and monitoring of the system, or greater reliability and availability to perform correctly in the event of fire. The Grade of fire alarm system that needs to be installed depends on the nature of the property, the level of fire risk and the characteristics of the occupants.
Grade F -  fire alarm systems, comprising one or more battery-operated smoke alarms, are the least reliable in the long
term because of the need for battery replacement. For new dwellings, a Grade D system (in which the normal power supply for each smoke alarm is derived from the mains electricity supply and a standby supply is provided) or higher is justified.
However, because of their low cost and ease of installation, Grade F systems (comprising battery-powered
smoke alarms) may be considered for installation in existing dwellings. Their reliability can be improved by use of batteries that have a long anticipated life and that cannot be removed without the use of a tool.
Nevertheless, Grade F fire detection systems are not appropriate in dwellings in which the fire risk to occupants is high
nor where there cannot be a reasonable certainty that, when the dwelling is occupied, batteries will be replaced within a short time (typically no more than five days) of a battery fault warning indication.
Otherwise, a system in which the normal supply is derived from the mains needs to be used (e.g. a Grade D
system).
If, in an existing dwelling, a Grade F fire alarm system would be acceptable, it is acceptable to install a Grade E system
(comprising mains powered smoke alarms). However, if there are likely to be periodic interruptions to the
mains supply, whether due to the inability of the occupier to pay for supplies or due to unreliability of the
mains electricity supply, a Grade D system or higher (in which there is a standby supply) is then necessary.

Where there is a need for readily accessible control of the fire detection and fire alarm system, a Grade C
system or higher might be provided. Where the fire risk calls for a high standard of system monitoring and
availability, it might be appropriate to install a Grade B system. If the dwelling is very large, or is subdivided into a significant number of dwelling units, a Grade A system is likely to be appropriate.
If the purpose of the system is property protection, fire insurers might require a Grade A system. However, for smaller properties, a Grade B or Grade C system might be sufficient.

Recommendations to consider when designing a residential fire alarm system.

The following items below are applicable when designing a fire alarm system in accordance with BS5839-6.
Any requirements imposed by enforcing fire authorities, and any requirements imposed by property insurers, for a fire detection and fire alarm system for a dwelling should clearly state the Category of system required.
If any party, (for example a fire alarm company),is instructed to design a fire detection and fire alarm system for a dwelling (e.g. by means
of a purchase or tender specification), the instruction should include a clear reference to the Category of system required.

Should a fire alarm or a fire detection system be intended to protect both life and property, and specific recommendations for the two Categories of system differ, then the system should comply with the
recommendations for each of the Categories.

Fire alarm design – Category PD

When design a fire alarm to a category PD, the following should be considered.

A fire can start virtually anywhere in a dwelling, although the probability of fire varies significantly from
one room to another. The probability of a fire occurring is usually ascertained by carrying out an on site fire risk assessment, as required by the FSO.

If a fire alarm system is not fitted and the fire is not detected at an early stage, it can grow until it becomes difficult or impossible to extinguish. The highest level of property protection will therefore be given by a Category PD1 system (giving full coverage of all parts of the dwelling). In a large house of high value, or with contents of high value, such a fire system is generally the only Category acceptable to fire insurers. The fire alarm system will normally have a facility for automatic transmission of fire alarm signals to an alarm receiving
centre.
A lower level of fire protection, still giving a useful reduction in fire risk, can sometimes be obtained by the fire alarm installation of fire detectors only in those parts of the building in which there is significant potential for ignition. A Category PD2 system provides partial cover of this nature.

Fire alarm design category LD3 residential

A Category LD3 fire alarm system is intended only to protect circulation areas that would be used as escape routes, by
giving a warning if smoke is detected in these areas, so that occupants can escape before heat or smoke make
this impossible. Therefore, the fire detection is positioned on the escape routes.

A Category LD3 fire alarm system cannot be expected, with any degree of reliability, to protect people who might be involved with the fire at ignition or in its early stages. This Category of fire system might not therefore prevent the death or serious injury of occupants in the room where the fire originates; it is intended only to ensure escape for those not immediately involved. If no fire detector is installed in the room in which fire starts, the time available for evacuation of other areas once fire is detected in the circulation area might be
quite short.

In a large family house adapted to provide accommodation for several households in separate self-contained units (a house in multiple occupation), a fire in one dwelling unit can be a hazard to occupants of other units.
In this case, the fire detection and fire alarm system normally needs to extend across the boundaries between occupancies or be interconnected with systems in other occupancies. In practice, it is often appropriate for there to be a single integrated fire detection and fire alarm system that will alert all occupants before a fire
in any dwelling threatens the communal escape routes, and that will provide early warning of any fire that starts in these escape routes. This objective is additional to that of enabling occupants of the dwelling in which fire starts to escape before their escape routes become impassable owing to heat or smoke.

In the case of purpose-built flats or sheltered housing, the degree of compartmentation between occupancies is normally sufficient to ensure that fire is contained in the dwelling of origin for a prolonged period. During this time, other occupants can remain in reasonable safety within their own dwellings. Accordingly, this part
of BS 5839 does not provide recommendations for fire detection and fire alarm systems that incorporate detectors in the communal areas or ancillary accommodation (e.g. plant rooms) within purpose-built flats
or sheltered housing. If, however, the provision of detection in these areas is considered desirable, it is essential to refer to the guidance contained in BS 5588-1, and it is appropriate that such fire detection and fire alarm systems comply with the recommendations of BS 5839-1.

Hotel fined after fire alarm system failed

I was reading a article on the “In4fire.com” website.

The article read as follows: Apparently, Magistrates have ordered a hotel manager to pay fines and costs totalling £5,355 after a fire detection and fire alarm system failed to activate in a fire situation.

Nine residents were staying at the Plume of Feathers at Harley, near Shrewsbury, in the early hours of July 27 last year when the wife of the hotel manager opened the bedroom door to find smoke in the corridor, according to Shropshire Fire and Rescue.

She tried to raise the alarm by activating manual call points but the fire alarm failed to activate. Her husband and other members of staff had to knock on bedroom doors to wake guests.

Area manager John Das-Gupta said that although the premises were fitted with a full automatic fire detection and fire alarm system, no fire alarm maintenance was in place, and it had not been adequately tested by the manager. Because of this, the fire alarm failed to operate and raise the sleeping occupants.

Michael Martin pleaded guilty to one offence under the Regulatory Reform (Fire Safety) Order 2005 at Shrewsbury Magistrates Court on 17 September.

The story above highlights the importance of having the fire alarm and any other fire protection equipment service and maintained in accordance with the relative standards.

Fire Systems Ltd, provide fire alarm maintenance and many other maintenance services. For more information contact Fire Systems Ltd, on www.firesystems.co.uk

Fire alarm systems for the protection for life – Category LD2

All HMO’s need to be provided with an appropriate fire detection and fire alarm system. The system installed can be a wireless fire alarm or a wired type system. The greatest benefit to life safety in a residential fire alarm is given by a full-coverage system (Category LD1). Such a fire system will give the earliest practicable warning of fire to occupants, wherever ignition occurs.

However, a good level of fire protection can normally be obtained from a Category LD2 designed fire alarm system, in which detection
is only provided at points where the fire risk is high or where combustion products would present a significant hazard to life. A Category LD2 designed fire alarm system might, for instance, have detectors only in the circulation areas of the dwelling, the living room and the kitchen; other areas might be left without detector coverage.
The areas protected by a Category LD2 system include escape routes, i.e. those areas that would be protected
by a Category LD3 system.

Wireless fire alarm are a popular choice in today’s residential market, due to the obvious ease of installation and little or no damage to the decoration. Fire Systems Ltd, are a industry known specialist for the installation of wireless fire alarm systems.

Fire alarm categories Part 6

Fire detection and fire alarm systems are usually installed in dwellings to protect life. However, the level of protection afforded to occupants needs to be related to the fire risk. The level of risk is usually established by carrying out a fire risk assessment.

The appropriate level can therefore vary considerably. For the purposes of BS5839-6, fire alarm systems are classified as follows, according to the level of protection that they afford.
Category LD: a fire detection and fire alarm system intended for the protection of life.
The designation “LD” is used to distinguish these systems, which are intended only for dwellings, from Category L fire systems
as defined in BS 5839-1, which are intended for the protection of life in any type of building.
Category LD systems are subdivided into:
Category PD: a fire detection and fire alarm system intended for the protection of property.
The designation “PD ” is used to distinguish these systems, which are intended only for dwellings, from Category P systems
as defined in BS 5839-1, which are intended for the protection of property in any type of building.
Category PD systems are subdivided into:

A fire alarm system is rarely installed solely for the protection of property. Accordingly, Category PD systems will normally be designed to comply with the recommendations of this part of BS 5839 for a Category LD system,
thereby constituting a combined Category LD and Category PD system.
Because of the wide range of systems covered by the recommendations of this part of BS 5839, the
specification of requirements for a system by a purchaser, user, enforcing authority or insurer, or the description of a system by a designer or installer, by reference to this standard, without a reference to system Category, will have little meaning.

Fire alarm grades residential

The following recommendations are applicable.
1) Any requirements imposed by fire authorities, and any requirements imposed by property insurers, for a fire detection, wireless fire alarm or a standard wired fire alarm system for a dwelling should clearly state the Grade of system required.

2) If any party is instructed to design a fire detection,wireless fire alarm or standard wired fire alarm system for a dwelling (e.g. by means
of a purchase or tender specification), the instruction should include a clear reference to the Grade of fire system required.

3) The relevant system certificate should clearly state the Grade of fire system that has been designed or installed.

In the case of a Grade A fire alarm system, there will be a separate design certificate, which will indicate the Grade of fire system that has
been designed . In other Grades of system, a single certificate will normally be issued, indicating the Grade of system
that has been designed, installed and commissioned.

Small fire alarm companies are struggling to survive in UK

As many as 45 small fire alarm companies within the fire protection industry are in financial difficulty as the lingering effects of the credit crunch continue to squeeze at the lower end of the market, according to a market analysts. The report states that smaller fire alarm companies have not had the same facilities to ride out the recession as well as their larger counterparts.

“While the larger fire alarm companies have relied on their size, brands and better access to cash, smaller companies have been left high and dry.”

“We have given 45 small companies a ‘Danger’ rating. While conditions have improved of late, I fear a high proportion will fail. Whereas large companies can call on banks and parent companies or cut out loss making parts of their operations, smaller companies are increasingly running out of cash.”

Another point is how small companies are struggling to maintain their market share and being squeezed out of the market. “209 small companies are selling less fire alarm and fire protection equipment  than last year. Clearly they have seen demand for their products dip or worse still, a new fire alarm company, has emerged. With their finances already stretched, they have little left in their arsenal to fight back.”

So what next for these small companies?  “There are clearly too many small fire alarm companies chasing too little market. The inevitable consequence is another round of consolidation with large competitors buying small companies at a discount. Of the 489 companies with assets of less than £3 million, we have identified 186 companies as being vulnerable to takeover.”

Fire alarm design residential

When designing fire alarm systems for residential properties, the following should be considered.

In the case of fire detection grades, Grade D, Grade E and Grade F systems, where more than one smoke alarm is installed the
smoke alarms normally need to be interlinked. Any heat alarms also need to be interlinked with the smoke alarms.
Guidance documents supporting legislation, and written requirements produced by enforcing authorities, often specify only a minimum level of fire system engineering, rather than a particular form of system. These Grades are defined in such a way that a requirement for one Grade of fire alarm system can be satisfied (normally at
higher cost) by the installation of a higher Grade of system; for example, if the fire risk justified the installation of a Grade D system, it would be acceptable to install a fire alarm system of an Grade A, Grade B or Grade C category.
Because of the wide range of fire systems covered by the recommendations of this part of BS 5839, the specification of requirements for a system by a purchaser, user, enforcing authority or insurer, or the description of a system by a designer or installer, by reference to this standard, without a reference to system
Grade, will have little meaning.
Annex B provides further information on each Grade of system, including the advantages and disadvantages of each Grade.

Fire alarm Grades in BS5839-6

The Fire alarm Grades are defined as follows.
Grade A: A fire detection and fire alarm system, which incorporates a fire alarm control panel and indicating equipment conforming to BS EN 54-2, and power supply equipment conforming to BS EN 54-4, and which is designed and installed in accordance with all the
recommendations of sections 1 to 4 inclusive of BS 5839-1:2002, except those in the following clauses, for which the corresponding clauses of this part of BS 5839 should be substituted.

Grade B: A fire detection and fire alarm system comprising fire detectors (other than smoke alarms and heat alarms), fire alarm sounders, and control and indicating equipment that either
conforms to BS EN 54-2 (and power supply complying with BS EN 54-4) or to Annex C of this part of BS 5839.

Grade C: A system of fire detectors and alarm sounders (which may be combined in the form of smoke alarms) connected to a common power supply, comprising the normal mains and a standby supply, with central control equipment.

Grade D: A system providing fire detection in the form of one or more mains-powered smoke alarms, each with an integral standby supply. (The system may, in addition, incorporate one or more mains-powered heat alarms, each with an integral standby supply.)

Grade E: A system of one or more mains-powered smoke alarms with no standby supply. (The system may, in addition, incorporate one or more heat alarms, with or without standby supplies.)

Grade F: A system of one or more battery-powered smoke alarms. (The system may, in addition, also incorporate one or more battery-powered heat alarms.)

Wireless fire alarm systems using detectomat

Fire Systems Ltd, is an approved agent for the supply and installation of detectomat wireless fire alarm systems.
Detectomat, a German based fire alarm equipment manufacture, has had a business working relationship with Fire Systems Ltd, for over 5 years.
The RCP6 is detectomat’s wireless fire alarm system available on the UK market.
A unique Wire-Free, Radio Fire Alarm System or also know as a wireless fire alarm system, offering an alternative to the costs, potential damage and business disruption associated with installing Fire systems in existing buildings. An An an ideal solution solution for retrofit and refurbishment applications in small to medium sized enterprises (buildings, office buildings, guest houses, restaurants, nursery schools, garages/workshops, large houses and houses in multiple occupation).
Radio as a Fire System communication medium has been available for many years but at a high cost. Now, the unique RCP 6B wireless fire alarm system offers a cost-effective wire-free, Radio Fire Alarm solution as an alternative to hardwired Conventional and smaller Addressable applications. And as an added benefit the system utilises detectomat's unique range of Designer cover Smoke Alarms to complement traditional or modern contemporary interior designs.

Fire alarm Open and Closed Protocols

what does it all mean?

Here Fire Systems Ltd, explain the differences between open and closed protocol fire alarm systems and outline the advantages and disadvantages of each type of system and what this could mean for the customer.

The term ‘protocol’, when used with reference to electronic products, refers to the way in which the products communicate with each other.  Within the fire alarm industry, Protocols are often referred to as ‘open’, ’closed’, ‘digital’ and ‘analogue’. It is important to be sure what each term means when comparing different types of analogue fire alarm detection systems.

In the fire detection industry, analogue addressable fire systems use control panels and detectors which communicate with each other by means of a protocol. Some fire equipment manufacturers offer both panels and detectors. These companies have no obligation to disclose the nature of their protocol to anyone, since they offer all the elements needed to provide an analogue addressable fire alarm system. No equipment supplied by other manufacturers is expected to be compatible with such systems, so the protocol used is said to be ‘closed’.

A number of manufacturers of detectors make no control panels; they have built up partnerships with independent panel manufacturers and, in some cases, companies who offer special equipment such as aspirating fire detection systems. The detector manufacturer determines the protocols used by the detectors and publishes the information and technical data required by panel manufacturers in order to design panels that will drive the detectors. Since all details of the protocol must be disclosed, it is referred to as an ‘open’ protocol.

Closed protocols

Manufacturers of equipment using closed protocols claim that all elements of their equipment (detectors, panels, call points, interfaces, special detectors such as beam detectors) will work harmoniously with each other, since it is all designed and made by the same company. The implication is that a fire system comprising detectors and interfaces from one manufacturer and panels from another cannot work as well with each other.

Open protocol

The manufacturers of the components of a fire alarm system with an open protocol would reply that products from different manufacturers of fire equipment work just as well with each other. Indeed, there might even be an advantage in having different specialist manufacturers concentrating on their own skills.

Fire alarms – Air Sampling Systems

Fire alarm designers have many different types of fire detection at their disposal. When early smoke detection is critical, air sampling detectors, “High Sensitive Smoke detectors” is the preferred choice.

Air Sampling is one of the most sensitive forms of fire detection currently available. By detecting smoke at an very early stage and taking appropriate remedial action the damage caused by fire and smoke can often be avoided.

An air sampling system is in affect a sensitive smoke detector and is usually interfaced to a fire alarm system. And it is the fire alarm system that initiates a full alarm to the rest of the building.

The design, installation, commissioning and maintenance of these sensitive fire detection systems is a specialist task and should only be undertaken by suitably qualified and equipped engineers.

Fire Systems Ltd, have been installing and maintaining Air Sampling Systems since 1992. Our staff have a great deal of experience in this field. We work with and install systems from all the major manufacturers, by being independent and not tied to any one manufacturer, our advice is completely impartial

Air-sampling Smoke Detectors work by:

1. Continually drawing air into a pipe network attached to a detector unit.
2. Passing the air through a dual stage filter to remove dirt
3. Sending the clean air to a laser detection chamber for smoke detection.
4. Measuring the light scatter caused by any smoke
5. Processing the detector signal and presenting the smoke level graphically
6. Communicating the information to a fire alarm control panel, a software management system or a building management system.

Air-sampling smoke detectors provide the early warning of an imminent fire hazard. Why is this important? It buys time. Time to investigate a smoke alarm. Time to take action. Time to avoid the danger, damage and disruption caused by fire.

Fire Alarm monitoring – Fire systems Ltd

 

By having a monitored fire alarm system you are ensuring that your property is watched over 24 hours a day 7 days a week. Monitoring has a wide range of applications including commercial, industrial, government and residential.

Fire Systems Ltd provide a remote monitoring service around the clock. This includes the monitoring of fire alarms and building management systems. When an fire alarm is activated, the ARC operators will immediately notify the emergency services in the event of a fire.. Keyholders and building managers are also notified.

Dual Alarm Receiving Centre

The Fire Systems Alarm Receiving Centre is the most advanced ARC in the world, providing you with the reassurance of monitoring 24 hours a day, 365 days a year. It also provides very high levels of security, as your alarm signal is directed into two of our ARC's simultaneously each site backing up the other.

The Benefits of Monitoring

• Peace of mind knowing that your property is being looked after 24 hours a day 7 days a week
• Fully endorsed by UK's leading insurers
• If there is an fire alarm activation Fire Systems will alert the emergency services to attend
• Saving you money by reducing your signalling costs
• By using non dialling technology your telephone line will not be interrupted

Fire Alarms interfaced to Fire Suppression systems.

When it comes to protected critical assets, a fire suppression system is an obvious choice.

London based fire alarm company Fire Systems Ltd, offer the complete package in fire suppression systems.

Ask yourself the following questions:

• Is your computer room equipment covered by your insurance in the event of a fire?

• What would be the consequence to your business if a fire was allowed to take hold in your server / comms room?

• It is not only your expensive hardware at risk, but your integrated custom software, your irreplaceable data, and countless hours of development time.

• Fire Systems Ltd, offer a bespoke design and implementation service that will provide the best solution for any technical room environment.

Fire Suppression systems offer extra peace of mind where buildings contain valuable equipment such as computers, vital communication rooms, data storage or valuable archives.

If a fire is detected the gas is discharged throughout the protected space, extinguishing the fire and causing minimum damage to the contents of the room.

Clean agent systems provide electrical non-conductivity, minimal down time to users following a fire and leave no residue, ensuring no clean-up and immediate business continuity.

Fire suppression 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. The is reduces down time and disruption to a minimum, provided, of course that any fire damage is minimal.

The fire suppression system is part of the main building fire alarm system. The main building fire alarm will accept the signal from the fire suppression system via an interface, and will usually have an independent zone on the fire alarm.

Fire alarm design recommendations

When designing fire alarm system, beams and other Similar Ceiling obstructions need to be considered and taken in consideration.
Fire detection should be mounted at least 500mm away from walls
or ceiling obstructions greater than 250mm deep and at least
twice the depth of obstructions less than 250mm deep. They
should also be mounted at least 1m away from any forced air
inlet. Where the obstruction is greater than 10% of the height of an
area it should be considered as a wall. Similarly a floor mounted
obstruction (such as racking) should be considered a wall if it
comes to within 300mm of the height of the detector.

Fire alarm detection - Lift Shafts
Where fire alarm detection is required in vertical shafts, such as stairwells,a detector should be mounted at the top of the shaft and within 1.5m at each level.

Manual fire detection - Selection of fire alarm manual callpoints
The selection of manual call points is somewhat simpler. Surface
or flush types are selected depending on the environment and
whether the fire alarm system is being installed into an existing building (where surface call points are generally easier to install). IP65
types should be specified where there is risk of moisture ingress,
for example in external locations. Standard fire alarm call points use a
frangible glass element which is designed to break under light
pressure triggering the call point into an alarm condition.
The glass element is covered with a thick plastic film to protect the
operator against broken glass, however plastic resettable elements
and protective flaps can be used where there is the risk of
unwanted operation or in food preparation areas. Where hinged
covers are used these should be recorded as a design variation.
Call points can be supplied with LED indicators mounted onto the
front face to simplify the location of an operated call point.

Addressable fire alarm detection zones

When designing detection zones for a addressable fire alarm system, the following recommendations are applicable.
1) Zone indication should be given at the fire alarm control panel even if addressable text information is also available.
2) An addressable fire alarm should give a text display of the location of, at least, the first detector to respond to a fire is available at the control and indicating equipment, without manual intervention; and
3) the display, if necessary in conjunction with other information on, or adjacent to, the fire alarm, would enable fire-fighters, unfamiliar with the building, to proceed to the location of the fire.
NOTE For example, the fire alarm control panel may provide a text indication of room number, and a plan adjacent to the control and indicating equipment may show the location of the room.

Remote indication of fire detection that has operated.

There is a need for having remote indication of an activated fire detector, should the fire alarm activate. Any remote indicators should be clearly labelled to indicate their function. They should be sited and/or labelled in such as way as to assist in determining the location of the detectors that they serve.
Any fire alarm wiring between a detector and a remote indicator required for compliance with this part of BS 5839

Fire alarm zone design considerations

When designing a fire alarm system in accordance with the standards, the floor area of a single zone should not exceed 2 000 m2. However, in the case of a zone comprising mainly a single, open plan area (e.g. an uncompartmented warehouse), which should not exceed 10 000 m2 in area.

Additional recommendations applicable to detection zones that contain non-addressable automatic fire detectors.

The following recommendations are applicable.
a) The floor area of a single fire detection zone of a fire alarm should not exceed 2 000 m2.
b) The search distance (the distance that has to be travelled by anyone responding to a fire alarm signal after entry to the zone in order for the location of the fire to be determined visually, see 3.50) should not exceed 60 m.

Having entered the fire detection zone, the person responding to the alarm signal need not reach the seat of the fire within the
recommended search distance; it is only necessary to become aware of the location of the fire.

In measuring search distance, the worst case, in which the fire is located at the furthest concealed area from any likely
point of entry to the zone, should be considered (see Figure 2).
c) fire alarm automatic fire detectors within any enclosed stairwell, liftwell or other enclosed flue-like structure
should be considered as a separate #detection zone. Manual call points located at final exits to open air
from stairwells may be incorporated within these detection zones [but may, alternatively, be
incorporated within the detection zone described in 13.2.1a)].

Fire alarm in residential properties

Fire alarm systems or smoke alarms are an important feature when discussing fire safety within residential properties.

The majority of fires in the home start in the kitchen, with the main
source of ignition being cooking appliances. Other causes of fire
include clothes being hung over heaters to dry and the misuse of
cigarettes and candles.
Electrical wiring and equipment can also be the root cause of electrical fires. Loose connections in electrical equipment and parts of the electrical installation (such as at accessories) can produce arcing and/or heating of terminations and conductors which can lead to a fire. Incorrectly selected fuses or circuit-breakers can also lead to
overheated cables.
To reduce the risk of fire causing harm or even death to your tenant(s) you will need to ensure that there is a fire alarm system and emergency lighting system (where required) installed and that they are the correct type for the property. You will also need to ensure they are regularly tested and and a fire alarm maintenance contract is in place.
In the event of fire, time is critical, having a fire alarm system, with well designed fire detection, will give you the extra time.

it is crucial that your tenant(s) can find their way out of the property to a place of safety. This means having a planned escape route which is free from clutter and having enough lighting to ensure a safe escape.

Fire alarm Hush Buttons

It is common place to specified a Fire alarm with a “Hush Button” facility within HMO’s.

Around 80% of all UK fire deaths and injuries occur in dwellings. Nowhere is the risk greater than in houses of multiple occupation where a fire in one ‘dwelling’ can quickly spread to another.

Unfortunately, an increased risk of fire means an increased risk of fire alarm systems, that produce false alarms. Failure to reduce false alarms can lead to unnecessary building evacuations, irate tenants, system vandalism and true fire alarm signals being ignored.

Hush Button fire alarm solution tackles all of these issues head on.

Designed to work with a wide range of fire alarm system protocols, from the leading fire detection companies, Apollo XP95 or Hochiki ESP analogue addressable fire alarm systems, it meets and exceeds the requirements of BS 5839 part 6 (the code of practice for fire alarm systems in dwellings) by providing reliable, fully monitored fire detection, alarm and silencing facilities INSIDE each individual flat or apartment.

Recommendations for fire alarm detection zones

If the fire alarm manual call points are located on the landings of an enclosed stairway, the manual call point on each level, other than a final exit level from the stairway, should be incorporated within the
fire detection zone that serves the adjacent accommodation on that level. A fire alarm manual call point located within the stairwell at a final exit to open air may be incorporated within the fire detection zone serving the stairwell.

If the total floor area of the building is greater than 300 m2, each fire detection zone should be restricted to a single storey.

If the total floor area of the building is less than 300 m2 a zone may cover more than a single storey.

When designing a fire alarm, voids above or below the floor area of a room, these may be included within the same zone of the room, provided that the voids and the room constitute a single fire compartment.

Fire alarm detection zones

In order to direct those responding to a fire alarm activation, particularly the fire brigade, to the area of a fire, all buildings, other than very small buildings, need to be divided into detection zones.

The fire detection zones need to be of a size, small enough for a fire to be located quickly.
Even if the fire alarm system is addressable, detection zone indication needs to be provided, as this often provides a quicker, albeit less specific, indication of the location of a fire than typical addressable fire alarm text displays. Zone indicators also provide a simple “at a glance” overview of the extent of fire or smoke spread.
If the fire alarm is raised by a manual call point, as opposed to an automatic detector, fire detection zone indication might be misleading; on discovery of a fire a person might operate a manual call point that is a considerable distance from the fire incident. The benefits of zoning in a Category M system are, therefore, less significant.

If a fire alarm detector is concealed in a relatively inaccessible area (such as a floor or ceiling void), it is normally
desirable to provide a remote indication of its operation. In an addressable fire alarm system, the provision of an
individual remote indicator might not be necessary provided that the location of each fire detector is clearly indicated at the control and indicating equipment.

Why do I need Fire Alarm Monitoring?

A question a person would ask a fire alarm company, is “Why do I need fire alarm monitoring"

The reason could be explained by the following. The majority of fires start after normal working hours, and if your premises are unattended, vital minutes can pass before a ringing bell gets noticed, and even if it was heard, would you be confident a passer by would react
accordingly and call the appropriate services. With fire
alarm monitoring, as soon as the fire detection has detected the fire, a signal will be on its way to a central monitoring station within seconds enabling them to summon the required help immediately.

24 Hour Alarm Monitoring
By having a monitored fire alarm system you are ensuring
that your property is watched over 24 hours a day 7
days a week. Monitoring has a wide range of applications
including commercial, industrial, government and residential.
A fire alarm company such as Fire Systems Ltd provide a remote monitoring service around the clock. This includes the monitoring of fire
alarm systems and building management systems. When an
alarm is activated, the ARC operators will immediately
notify the emergency services in the event of a fire.. Keyholders
and building managers are also notified.

Fire Alarms

Automatic fire alarm systems provide the earliest possible warning of a fire situation, enabling the building to be safely evacuated if required and the fire tackled in a safe manner.

Fire Systems Ltd, design, supply, install, commission and maintain fire detection systems, fire alarm systems, and especially wireless fire alarm systems.

Business has a duty to provide and maintain effective systems to ensure legal compliance and the requirements of most insurers is met by our:

• Biannual or quarterly service of your fire alarm system in accordance with the Regulatory Reform (Fire Safety) Order 2005 and in compliance to BS 5839
• Our engineers trained to service a wide range of fire detection systems by various manufacturers, covering open and managed protocol fire alarm systems

Our experienced and highly skilled fire alarm engineers will work with you to support your business in the best possible way.

Why not visit our website for more information, on www.firesystems.co.uk

Fire alarm test and inspection

In the form of two six monthly fire alarm maintenance visits, the following work is to be carried out every year.

The switching mechanism of every fire alarm break glass call point should be tested, either by removal of a frangible element, insertion of a test key or operation of the device as it would be operated in the event of fire.

All automatic fire detection devices should be examined, as far as practicable, to ensure that they have not been damaged or painted. Then every fire alarm detector should be test-operated. The tests used need prove only that the detectors are connected to the fire system, are operational and are capable of responding to the phenomena they are designed to detect; they need not prove the sensitivity of the detector.

Smoke detectors should be operated by a method that confirms that smoke can enter the detector chamber and produce a fire alarm signal such as simulated smoke or suitable aerosols. Use of a test button or test magnet, does not satisfy this recommendation.

Every heat detector should be operated by means of a suitable heat source, unless operation of the detector in this manner would then necessitate replacement of part or all of the sensing element (e.g. as in fusible link point detectors or non-integrating line detectors).

All of the above, should be part of your fire alarm maintenance.

Fire alarm maintenance and routine testing

Fire alarm maintenance is a legal requirement under the Fire Safety Order 2006. Although your fire alarm system incorporates a high degree of monitoring so that faults are indicated automatically, it is still necessary for you to ensure that all fault indications that appear on the fire alarm panel are identified so that you can take appropriate action. The importance of regular testing being carried out is to ensure that there has not been any minor or major system failure, between the visits for the fire alarm maintenance. It also helps the site personnel to familiarise themselves with the operation of the fire alarm panel and testing of the fire detection.

The routine testing of the fire alarm system also provides an opportunity for all the occupants of the building to become familiar with the alarm and the signals that it produces. If your alarm has staged signal that give both an “Alert” and an “Evacuate” alarm, both signals should be operated when each test is carried out to ensure that the occupants are aware of the existence of both signals and their different meanings.

Fire alarm maintenance, should be carried out as a minimum, every six months.

Fire Alarm issue at Euston station

Issues have been raised as to  whether fire alarm and fire detection equipment was working properly when apparently, smoke was spotted coming from an escalator at Euston Underground station last month.

Tube union RMT claims that on 6 July, a major disaster was only averted by the actions of a member of staff spotting the smoke and raising the alarm. But Transport for London (TFL) which is responsible for London Underground, says that fire alarm systems were working but that the employee spotted the fire before the fire alarm had time to activate.

The station was evacuated and closed for around an hour while London Fire Brigade crews attended the incident. They discovered smoke coming from a cable inside an escalator panel.

At Oxford Circus station, In another incident last Friday, 15 fire fighters attended a small fire in a wall mounted air conditioning unit. The station was evacuated for a few minutes but damage was limited to a small amount of wiring within the unit.

RMT has concerns regarding the fire alarm and fire detection equipment and has put in writing, a request, that all fire alarm detection equipment at sub-surface stations be inspected within 72 hours.

Meanwhile, RMT members voted yesterday to take industrial action in response to proposed budget cuts to London Underground, and the union says that staff who spotted the fire are among 800 jobs that are threatened.

Referring to the Euston station fire, a London Underground spokesperson said: London Underground has carried out a full investigation and re-tested all fire alarm systems at the station, to ensure they are fully working.

“The fire alarm system would have been automatically activated within the standard time frame of two minutes, as is the case across the London Underground. However on this occasion, a member of staff raised the alarm within this time frame.

“London Fire Brigade gave permission to reopen most of the station within an hour. If they had any serious and ongoing concerns about our fire alarm, they would not have done so.”

The type of fire detection underneath the escalators is a fibre optic linear detection system.

fire safety and fire alarm breaches at CLG headquarters

We can today reveal that the London headquarters of Communities and Local Government – the government department that steers fire safety policy in England and Wales – has been served with an enforcement notice under the Regulatory Reform (Fire Safety) Order 2005.

In a damming review of the building’s fire safety, an inspector from the enforcing authority, states:  “The concepts of ‘responsible’ and ‘competent’ persons, and the duties placed upon those persons under the Order, appear not to be understood within CLG premises”.
The notice, served on 16 February on the then secretary of state for Communities and Local Government, John Denham, details numerous shortcomings in fire safety measures and management at CLG’s Eland House premises in Victoria. It lists alleged breaches of 13 of the 15 Articles of the Fire Safety Order that impose duties on the CLG, as the responsible person, including:

• Introducing a fire load in the atrium which was not considered in the building’s fire engineered design, by installing a cafeteria which, it is said, may lead to “uncontrolled fire spread throughout the building”
• An unsuitable and insufficient fire risk assessment
• Failing to nominate competent persons to help the responsible person discharge his duties
• Failure to adequately provide fire alarm maintenance for the fire alarm system, interconnections between fire alarm systems, and smoke vents throughout the building
• Lack of evidence of adequate training and provision of essential fire safety information to staff

In an apparent reference to other CLG premises, the inspector goes on to say: “At present there is a lack of national policy, guidance and ownership of fire safety management across the CLG estate.”

Details of the fire inspection and the enforcement notice have come to light under a Freedom of Information request made to CLG by an individual linked to the fire safety industry.
“Unacceptable” policy
Other deficiencies found include an “unacceptable” policy that no one should use portable fire extinguishers in the building; the inability of the building to support the phased fire alarm evacuation strategy; no adequate arrangements to ensure visitors and contractors are accounted for in an fire alarm evacuation; and shortcomings in the means of escape for the number of people likely to occupy the building.

Although Eland House is categorised as Crown premises, it is still subject to safety legislation including the Regulatory Reform (Fire Safety) Order, and enforcement procedures are similar to those of other premises. However, Crown Immunity means the responsible person cannot actually be prosecuted for offences.
The enforcement notice also reveals that the contracted facilities company, having some control of the premises, was sent a copy of the notice. However, it makes it clear that although the company is considered a ‘nominated competent person’, they had not been provided with sufficient means to carry out their duties.

We at Fire Systems Ltd, find this story extraordinary, as this is the governing body responsible for ensuring we all abide by the new legislation. And to add insult to injury, they are immune from prosecution.

They appear to have failed on so many basic items, such as fire alarm maintenance, fire alarm interconnection, supplying a expectable fire risk assessment.

The Benefits of Wireless Fire Alarm Systems

Radio or wireless fire alarm systems first became available in the early 1980’s. In these early days of radio, the early radio or wireless fire alarm systems began to gain a poor reputation for reliability, mainly related to the radio transmissions and battery life of the devices and poor fire alarm design.  However over time the technology involved in these fire systems has steadily advanced to where we are today.  Today’s Radio or Wireless Fire Alarm Systems are light years ahead of their early 80’s ancestors.  Interestingly the advance in technology with the radio fire alarm systems has occurred as a bi-product of major advances in technology in the computer, battery and mobile phone industries.  Radio Fire Alarm System designers and engineers have embraced and harnessed this new technology to create and manufacture a new generation of radio fire alarm systems that are much more sophisticated in terms of performance, fault monitoring and reliability.  These new systems are fully compliant to BS5839 and EN54 and are fully monitored.

One of the main benefits of A Radio Fire Alarm System is that they reduce the needs to install cabling to each individual device on the fire alarm system.  Modern radio fire alarm systems will only need cables to be installed to the control and signal booster panel positions to provide a mains supply.  This benefit of radio fire alarm systems means that have been ideally suited to listed type buildings.  It allows the installation of a fully functioning fire alarm system within the building while not ‘running’ cables where it is impractical to do so.  Examples of installations of this type are in Windsor Castle and The Ritz Hotel, both of which have radio fire alarm systems installed.  In some instances conservation bodies would also prohibit the installation of cables within protected buildings and radio fire alarm systems may be the only solution to allow the building to comply with current regulations and standards.

Fire alarm monitoring and reliability cont.

Note that duplication of fire alarm sounder circuits throughout a building is not generally necessary and can even fail to achieve the objective outlined in the previous blog. In this case, if fire damages one circuit, it is also likely to damage any other circuit in the same area. However, in a large building with multiple sounder circuits, each serving a different area of the building, the above objective is satisfied. In a smaller building, which could, otherwise, be served by a single sounder circuit, additional measures will be necessary to ensure that, if this single circuit fails during a fire, at least one sounder (e.g. on a second circuit) continues to operate.

However, in buildings designed to accommodate the general public in large numbers, typically within a single space, the threat to life in the event of a fire may be such that additional fire alarm device circuits,
over and above those described above, is justified; this then addresses the remote possibility of failure or impairment of a single circuit serving a large public space at the time of a fire. Frequently, such buildings are served by a voice alarm system interfaced to the fire alarm system. In the case of such fire systems, BS 5839-8 recommends additional loudspeaker circuits in large, un-compartmented public spaces of public buildings such as transport
terminals, shopping malls, places of entertainment, large department stores and leisure centres. The size of the un-compartmented public space above which additional loudspeaker circuits are recommended by BS 5839-8 is entirely arbitrary but, for consistency, if such a large public space is protected by audible fire alarm devices, duplicated and evenly distributed fire alarm device circuits need to be installed within the space; such duplication is, however, not necessary in other parts of the building.

A Fire alarm system design needs to be arranged to limit the extent of impairments, whether as a result of faults or work on the Fire alarm system. A fault (but not fire) signal needs to be given at the control and indicating equipment in the event of any failure in the critical signal path (see 3.13).
Care needs to be taken in the use of multi-core cable for the wiring of more than one circuit. It needs to be
assumed that any fault that affects a multi-core cable affects all conductors of the cable; this precludes the
use of multi-core cable for certain applications in which the failure of more than one circuit as a result of a
single fault is precluded by the recommendations of this standard.

Fire alarm monitoring of external circuits

12.Fire alarm Monitoring, integrity and reliability of circuits external to control equipment
12.1 Commentary
External circuits external to the fire alarm control equipment, need to be arranged such that the probability of faults that could prevent the fire system from giving a fire warning is minimized. Such faults will, however, occur occasionally. Work on the fire alarm system, for
the purpose of modification, repair or routine fire alarm maintenance, may also cause an impairment of the fire alarm system to operate as designed in the event of fire.

Measures are incorporated within this code of practice to limit the probability of impairments, whether as a result of faults or work on the fire system, and to limit the duration of any impairment. The wiring of all critical signal paths is protected against mechanical damage and damage by fire. Critical signal paths are monitored, so that faults will be identified quickly. Compliance with the recommendations for fire alarm maintenance arrangements ensures that any such fault is quickly repaired. The probability that a fault will exist at the
time of a fire is, therefore, considered to be extremely low. In the event of fire, fire damage to wiring during the period required for evacuation is unlikely to occur in view of the recommendations of this code of practice for the fire resistance of cables.
As a result of the above considerations, duplication of, or redundancy in, external circuits is not normally necessary. However, in the case of circuits serving fire alarm devices, special measures need to be taken to ensure that, during, or following, evacuation, damage to any wiring, with resultant loss of the evacuation signal, does not imply to occupants of the building that it is safe to remain in, or re-occupy, the building.
This can be achieved by ensuring that, in the event of a short circuit developing on any fire alarm device circuit during a fire (e.g. at a cable termination), a minimum of one audible fire alarm device continues to
sound as a reminder that the system has not been silenced or reset. Normally, this sounder is located close to the control and indicating equipment, as this equipment will be sited in a suitable area (e.g. a reception area, security control room or main entrance foyer) at which the reminder needs to be given.