Clients are increasingly demanding the installation of radio fire detection and alarm systems. We outline some of the advantages and disadvantages of such sysyems.
A wire-free fire detection system utilises secure, licence-free, radio communications to interconnect the sensors (smoke detectors, manual break-glass callpoints, etc) with the fire alarm control panel. The sensors are typically self-powered with built in energy packs. A simple concept, but one that brings many advantages through the elimination of expensive fire-rated cable.

The use of wireless signalling has been around for over 30-years, with the majority of the early products coming in from the US or the Far East. The integrity of radio fire systems has improved considerably over the years, in part due to the involvement of UK manufacturers with backgrounds in high security radio applications.

In 1988 the revised BS 5839 – ‘Fire detection and alarm systems for buildings’ – was published and included the acceptance of radio as a means of signalling fire alarm systems.

The Radio Communications

Agency tightly controls the radio frequencies available for use in the UK and only agrees their operation after they have been tested and proved to meet the relevant standards. This means any radio equipment used on a particular site must carry the appropriate approval, and that there should be no mutual interference between any of the systems.

Part of the Radio Licensing Authorities remit is to ensure that each of the major services has its own separate allocation from within the frequency spectrum. For instance, each of the following applications are segregated to prevent interference:

  • tv broadcasting
  • Emergency services;
  • mobile telephones;
  • private mobile radio;
  • airport ground support;
  • radio microphones;
  • car alarms (key fobs).

This segregation together with the secure dual-frequency signalling that modern radio alarm systems use, ensures that false alarms due to radio interference cannot occur.

Modern radio fire systems are analogue addressable and provide all the features you would expect from any fire detection system, including networking (radio based), repeater panels, paging and cause and effect programming. The devices used are often based on industry standard sensors, sounders and callpoints and are aesthetically pleasing with built-in aerials that are hidden from view. Many radio systems also incorporate industry-leading products such as multi-sensor fire detectors and combined sounders and fire detectors in one unit.

Where can you use radio systems?

There are few instances where radio fire alarm systems cannot be used, however, in practice radio fire systems can be installed in almost any commercial and industrial application. There are however, a number of applications where radio systems can provide significant advantages.

A hotel or residential home can be refurbished with a new radio fire detection system without effecting room occupancy and services. A bedroom can be fitted with a fire detector and sounder in less than 10 minutes.

Environments such as building sites and entertainment events that require temporary protection are suitable applications for the flexibility of radio systems. The detection devices can be easily changed as the environment changes and the systems can be either rented for short-term applications or purchased and moved to the next site upon completion. Radio can also be an ideal solution for many commercial installations where full protection is required in the interim, but the final installation would form part of the tenant’s fit out package.

Historic buildings or existing buildings with high grade/expensive finishes requiring refurbishment can have a radio system installed without disturbing the décor.

Buildings with asbestos materials that would be uneconomical to remove can be easily protected without disturbance. Devices such as smoke detectors can be fitted to ceilings without the need for drilling.

Radio systems are also suited to open-plan buildings without suspended ceilings and benefit from the reduction of visible exposed services and wireways. The protection of open plan offices can be easily moved as the environment changes without the need to move or re-run cabling.

Developments or sites with multiple buildings requiring central control can be fitted with a radio system thereby removing the need to interlink buildings with cabling. This eliminates expensive external infrastructure works.

Medium and large developments can benefit from a reduced programme through the reduced labour time associated with radio alarm systems. A typical radio smoke detector takes just 10 minutes to install.

Radio systems can be easily interfaced to existing or obsolete wired systems, which require expansion or upgrading.

Advantages and disadvantages

Radio systems can be much easier, quicker and cheaper to install. Independent research

conducted by cost consultants Davis Langdon & Everest concluded that on many typically sized commercial installations, radio alarm systems were cost competitive with hard-wired systems. On large installations they were cheaper due to the significantly reduced labour costs. On refurbishment projects, particularly in historic and listed buildings the advantages are more significant.

There is also much greater flexibility in positioning of devices. This flexibility allows for the design and installation to be detailed late in the program, thus eliminating the cost and time involved with late client changes. Additional devices such as smoke sensors and callpoints can be incorporated, removed or repositioned with minimal disruption.

The system can also be easily modified and expanded in the future even when the building is occupied.

Wire-free systems also eliminate disruptive and damaging installation works. A typical radio device such as a smoke detector can be installed in less than 10 minutes, this reduces the disruption of services and normal activities during refurbishment to occupied buildings. This also has a cost advantage in applications such as hotels, dealing rooms and residential homes where building occupancy would be largely unaffected.

Since no cables or wireways are required, damage to the fabric of the building is significantly reduced, which is an important consideration in historic buildings.

A further advantage is that multiple building protection avoids infrastructure costs. Multiple buildings can be linked without the use of interconnecting cable thus avoiding expensive external infrastructure works. The cost to dig up ground, install underground ducts and refill could have a major impact on a project. Even overhead cables could have a similar impact.

Radio links will operate without impairment during a fire unlike wired fire alarm systems which rely on expensive fire-rated cable to ensure continued safe operation during a fire. Radio systems eliminate this need as the signalling is unaffected by fire.

Radio systems can also provide more secure installation. Assuming a thorough radio survey has been undertaken and the system has been installed correctly the risk of damage or corruption to the signalling path is eliminated. There are no cables to break or short out. Radio systems are tolerant to hostile environments as is born out by the type of installations that currently exist including MOD bases, airports and air traffic control centres.

As with most things however there are disadvantages to radio systems. The costs of devices and control panels are higher compared to typical wired-systems due to the additional radio electronics and local power requirements. However, the equipment cost cannot be taken in isolation and total project costs need to be considered in the light of the reduced installation costs. Typical cost breakdowns are shown in figure 1. The reduced labour cost typically offsets the higher equipment cost.

Power is also required for devices, this can be locally powered either from a power supply or batteries. Modern radio devices have built-in battery power packs, which typically give each device a five-year life under normal operating conditions before they need replacement. Normal operating conditions include regular system tests, including sounders, as specified in the standards. Typical battery packs use lithium batteries but the latest devices now incorporate alkaline batteries which further reduces replacement costs and addresses the environmental issues of using lithium batteries.

The health of each battery pack is monitored by the system and a low battery warning is raised well in advance, often allowing battery replacement to be undertaken during normal maintenance.

Clearly there is an additional on-going maintenance cost with radio systems but with the lower costs associated with alkaline batteries and the need to perform cable integrity checks are eliminated there is little difference between radio and wired systems. The alkaline batteries used can be replaced with off-the-shelf batteries bought from the high street and do not require the purchase of specialised modules from the supplier.

Radio survey

Before any design or installation is undertaken it is essential that a trained qualified engineer should carry out a radio survey. The survey will determine the most appropriate radio receiver, transmitters, type and location of aerials and positioning of devices. This is an essential exercise, and it is important that this process is performed with the utmost care to provide reliable trouble-free operation.

The future for radio systems

Radio systems are now becoming increasingly significant not just in fire detection but also in high security applications and voice evacuation. The integrity, reliability and flexibility of radio fire systems have been incorporated in products that can solve a diverse range of security applications. All the advantages of a wire-free environment are just as relevant for security as they are for fire systems.

One other area in which radio is making a significant impact is that of voice alarm and evacuation systems. Radio systems can now provide building-wide voice evacuation including public address facilities without the need for cable.

These systems can easily be interfaced with radio fire and security systems to provide site-wide fully integrated wire-free protection systems.

Imperial College the engineering university at South Kensington, London became recipients of radio fire and voice evacuation systems in providing total protection to their new Flowers and existing biochemistry and chemistry science research buildings. Installed during 2000-2001 the installations were natural choices due to the nature of the buildings internal construction.

The Flowers building lent itself for wire-free protection because all services are totally exposed – there are no ceilings. The building however was to house some extremely sensitive equipment in the form electron microscopes, nuclear magnetic resonance and x-ray machines as well as super computers carrying out some ground breaking research. The architect was keen to reduce the cable clutter inherent with an exposed services scheme and a wire-free system was a natural choice. To prove that the system would work reliably in such an environment, the client and design team were subjected to numerous demonstrations and test. With the new build two radio surveys had to be carried out, the first prior to construction where the surrounding buildings were checked for any possible external influence interfering with the new building, and the second with the building construction complete and the major services installed.

The radio network consists of three controllers communicating over 350 devices, and has been a complete success.

The biochemistry and chemistry buildings are existing, adjoining 1960s constructed research facilities occupying some 16000 m2 of space. The criteria for these buildings were the fact they needed to replace an out of date fire alarm system prone to numerous false alarms that was disruptive to many of the research work being undertaken.

Since it would have been difficult to replace the system without disrupting the research work, the removal of ceilings and drilling holes into walls as well as removing the existing cables was considered impractical. Since work to the Flowers building was in progress, the wire free solution was the practical and most economic choice.

The radio network consists of five controllers communicating over 625 detection devices and 276 voice speakers. The installation was achieved in a sixth of the time programmed for a wired system with the minimum of disruption to research works being carried out. The success of these installations at Imperial college has set the trend for the total upgrade to the whole campus fire alarm refurbishment programme.

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