Our communities draw strength and inspiration from national treasures, and here, Aston Bowles describes the special approaches involved in keeping heritage sites and their occupants safe from fire
WHERE ACTIVE fire protection is concerned, the fabric and contents of heritage buildings present distinctive and complex challenges. The buildings are frequently made of easily combustible materials, their layout and infrastructure can be confusing or difficult for users in evacuation, and the detection methods required to protect the sites can be demanding.
Add to this the fact that heritage buildings may house residents and often receive many visitors, that installing protection systems in them can be difficult and that the industry faces a unique challenge. Fortunately, the flexibility and performance required to meet this challenge are offered by some modern fire systems.
The Regulatory Reform (Fire Safety) Order 2005 stipulates that all reasonable steps must be taken to keep buildings safe and protect the people using them. A comprehensive fire risk assessment needs to be carried out and, in the case of heritage buildings, this needs to be supplemented normally with a more in depth fire safety management plan. This should cover important aspects such as active and passive protection measures – both those that are in place and those required – mitigation of identified risks, staff training, maintenance and review periods.
At the heart of the system will be a fire panel – single or multi loop, standalone or networked – and the choice available is wide, but not simple. The installation costs are likely to dwarf equipment prices, so finding a system that is easily installed and has flexible cabling and a range of communication options should be the priority.
Each heritage site is unique and such sites are therefore likely to be connected to alarm receiving centres (ARCs), or are often in remote locations with difficult access. If a low quality, unreliable or unsuitable system is installed, the downstream costs of fault finding, repair and maintenance can be significant.
Another important consideration when choosing panels for heritage sites is the degree to which they allow you to subdivide and manage different building areas. The fire system should offer many, easily programmed cause and effect options to accommodate the wide range of room sizes, layouts and uses frequently found in such buildings.
A common panel challenge in this context is to ensure that the system is made as unobtrusive as possible, without compromising performance. By using repeater panels, the larger more obvious primary fire panel can be hidden from view in an office or service room.
More aesthetically pleasing and easily disguised repeater panels are now available, such as the Advanced TouchControl touchscreen, on which images and public information can be displayed when not in fire mode. An alternative approach is to create bespoke cabinets and housings for panels, which can be tailored to fit seamlessly into almost any decorative scheme or space that is hard to access.
Many factors can impact the performance of the fire system, and these are often exacerbated in heritage buildings. Unusual room geometry, large windows, archways, draughty fireplaces and high, irregular, suspended or decorative ceilings can create detection challenges.
The performance of a fire system can be influenced by many factors including unusual room dimensions, outsized apertures, arcades, draughty fireplaces and high, irregular, suspended or moulded ceilings. Making sure that smoke or relevant signals reach detectors is the primary consideration. Given the unpredictable nature of fires and the different materials that are involved in heritage constructions, detector choice and system programming are critical in a heritage building.
Multiple detection methods can be specified and each country will have its own guidance that should be used. In the UK, the Bible for detector placement is BS 5839, which provides
in depth direction on the standards for the various detection types in unique spaces.
Types of detector
Optical smoke detectors remain the default choice, while heat detectors are commonly employed in utility spaces, such as kitchens, where cooking smoke and steam are likely sources of false alarms. Multisensor detectors bring together heat and smoke detection in one unit and have widespread uses, including on some systems helping to ensure that a fire incident is valid by checking the smoke and heat signals independently. The sensing technology and processing power of point detectors increases every year, and the latest detectors offer real performance and sensitivity gains. Not all smoke detectors are the same.
Because the floors and ceilings in heritage buildings are commonly made from wood or stone, fitting cable based systems to permitted regulatory standards can be complex and expensive. Wireless detectors are simpler to fit and less obtrusive. They still require wireless receiver modules, which are wired into the panel loops, but the detectors themselves require no cabling and include many sensing and indication options.
Some ranges also come in decorative finishes that allow them to blend in with the materials in a heritage site, such as wood or stone.
Aspirating detectors are an increasingly widespread method of fire detection. They work by continually sampling the air through a network of pipes that connect to a central, highly sensitive detector and, although the associated pipework can be bulky or unsightly, they are a viable option when installed in secondary spaces such as basements and lofts. They can even be run inside sealed display cabinets where necessary, to protect high value items.
Smoke dissipates differently in taller spaces, so point detectors (under BS 5839) are inappropriate for rooms above 10.5m. Here, beam detectors are an invaluable tool. These are quick to install and very effective. The only downside is the need for a reflector on the other side of the room or space, so they are vulnerable to movements in older buildings, although some newer versions can self align.
An additional technology is video and charge coupled device (CCD) driven flame detectors. While in most cases flames will be detected after smoke, these devices are useful where visible flame fires are more likely to occur and some can also show live video of the space in question for confirmation purposes.
A final detector type is linear heat cable. This can be run through any area to provide rapid warning of a fire. Tiny variations in temperature cause the current in the cables to short, notifying the fire panel of a fire. In some systems, this location can be precisely identified.
Case study - Lincoln Castle
WITHIN THE treasury at Lincoln Castle, which is home to a priceless copy of the Magna Carta, an Advanced AmiPro fire panel has been combined with an ExGo suppression control panel and fire suppression gas to protect the vault. In addition, a wireless reflective beam smoke detector from Hochiki has been installed, with an automatic realignment feature.
Automatic door controls now isolate the space, preventing any fire from spreading and ensuring that the gas is concentrated correctly. In order to minimise the amount of cabling required and limit any disturbance to the fabric of the building, hybrid wireless fire detection products have been installed; while in the vault itself, all components have been specified to blend into the decorative scheme.
As the contents of heritage sites are often more valuable than the structures themselves, best practice states that important areas, such as gallery spaces, state rooms and archive stores, should be afforded a higher level of detection, using single or multiple detector types so that incidents can be verified rapidly. Rapid detection is the priority and extinguishing via sprinklers, water mist or, in high priority areas, suppressant gas or foam should be considered. The case study (see previous page) is a brief example of the tailored approaches and special considerations required in heritage premises.
The primary task of any fire system is to save lives, but longer, more complex, escape routes are a major challenge in heritage properties, especially those converted into hotels or apartments. Speed is of the essence in such sites, and panels and networks should be chosen for this consideration.
Cause and effect programming can verify that the alert is genuine and then control the evacuation of the building. Automated paging systems use vibrations to ensure that residents with hearing impairment are alerted and modern emergency lighting systems can help ensure safe evacuation.
Fire panels in heritage buildings are often linked to alarm receiving centres (ARCs), many of which may now require human validation of a fire incident. Modern panels have a variety of ways to achieve this, from verification times and investigation delays to outputs, either automatically or with the help of responsible people or trained occupants.
Rather than use general or local alarms, radio paging systems can alert staff as soon as the incident occurs, and sometimes even before a detector reaches threshold. Using the nearest fire panel, trained personnel can then determine the location of the incident and validate it before overseeing an orderly evacuation or resetting the panel if no fire is present.
Also, a new generation of touchscreen graphical panels and repeaters is assisting evacuation and firefighting in complicated sites, and they can display maps or plans of buildings with zone status.
Heritage buildings will always present extra challenges in terms of fire detection and alarm, but innovations in fire system technology have led to major developments in this area that benefit occupants, owners and fire professionals. A system that has been well thought out can protect any heritage site, as well as the people and artefacts it contains, enabling speedy evacuation and ensuring that fires are controlled and extinguished as rapidly as possible.
Aston Bowles is head of marketing at Advanced Fire Systems Limited. For more information, view page 5