Maximising fire system effectiveness in historic buildings
Historic buildings pose a complex challenge for those tasked with protecting them from fire. The threat and consequences of fire in any building are serious. However, in the case of historic sites, the loss of irreplaceable artefacts of high monetary and historic value is permanent and costly to our heritage.
Added to this, these buildings frequently have permanent staff and attract high numbers of visitors, so life safety must be of paramount importance.
Finding the optimum balance between the protection of people and property and preservation of the aesthetics and authenticity of the building is contentious and will always require compromise.
Complying with regulations
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. An in-depth fire risk assessment needs to be carried out and, in the case of historic buildings, normally needs to be supplemented with a more in-depth fire safety management plan. This should cover important factors such as active and passive protection measures – both in place and required – mitigation of identified risks, staff training and maintenance as well as review periods.
Choosing the right system
At the heart of the system will be a fire panel – single or multi-loop, standalone or networked – 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 with flexible cabling and a range of communication options should be the priority.
The unique nature of heritage sites means they are likely to be connected to 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 historic 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 heritage buildings.
A common panel challenge 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 aesthetic 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 hard –to-access space.
Many factors can impact the performance of the fire system, and these are often exacerbated in historic buildings. Unusual room geometry, large windows, archways, draughty fireplaces and high, irregular, suspended or decorative ceilings can create detection challenges.
BS5839 is the bible for detector placement and gives detailed guidance on the standards for different detection types in unusual spaces.
Particular care must be taken to ensure that smoke can reach detectors, and that it is not shielded from them. It is also important to place detectors in such a way that smoke does not stratify beneath the detecting element or otherwise delay or stop the efficient detection of smoke. If we add in the nature of the fires that different materials will create and the likely speed of spread of fire in an old building, detection choice and system programming become critical.
There are many different detection methods suitable for historic buildings and it’s common to find many of them across a single system. Modern point detectors are hugely reliable and the most common type is still the optical smoke detector, with heat detectors employed in spaces such as kitchens where steam and cooking smoke are often present. Multi-sensor detectors combine heat and smoke detection in a single unit, helping to ensure that a fire incident is real and avoiding false alarm incidents.
Because the floors and ceilings in older buildings tend to be wooden, fitting cable systems to approved modern standards can be a huge logistical challenge, as these usually require suspended steel trays. A much less invasive option involves using wireless detectors. The wireless receiver modules still need to be wired to the panel network, but the detectors themselves can be placed much more discreetly and they are available in virtually all the most common variants – smoke, heat, ionisation and multi sensors.
Wireless solutions not only mean lower visual and physical impact, they are also faster to install and so can help to keep costs down. Thanks to two-way communication with the panel, battery replacement and fault reporting can be worked into the on-going maintenance schedule, which is particularly useful where a scaffold is required to reach specific components.
Where early warning is crucial, such as a gallery space or archive store, aspirating detectors offer a highly effective solution. These continually sample the air, several times a second, and can be set at various sensitivity levels. Although the associated pipework can be bulky and hard to conceal, they are still a viable option when located in less prominent spaces such as cellars, service areas and attics.
As smoke and heat detectors are unsuitable for ceiling heights over 10.5 metres, due to the way smoke dissipates in taller spaces, beam detectors can be used in larger rooms, such as great halls or chapels. These are simple to install and can function wirelessly. The need for a reflector on the other side of the room can make them sensitive to movement, particularly in timber-framed buildings, although some newer beams do self-align, minimising the effects of building movement.
Another option is video and CCD driven flame detectors, a technology that has developed rapidly in recent years. Although flames will often, although not always, be detected after smoke, these are useful devices where quickly visible flame fires are more likely.
A final detector type for sensitive installations is linear-heat or heat-sensing cable. This can be run through any area to provide early warning of a fire. Minute changes in temperature cause the conducting cables to short, thus identifying the location of the heat source and alerting the fire system. In London, the reconstructed Globe Theatre was able to get around a 400-year-old ban on thatched roofing using this system. The cables run through the thatch and connect directly to the fire panels, giving early indication of any incident.
Another key to effective fire safety is to ensure that critical and high risk areas, such as kitchens, boiler rooms or gallery spaces, are specified for a higher level of detection, using single or multiple detector types, so that incidents are confirmed as quickly as possible and action can be taken without any delay.
Fires can spread very quickly in historic buildings, so measures to allow quick extinguishing via sprinklers, water mist or, for high priority areas, suppressant gas or foam should be considered.
The intelligent zoning of fire systems can be combined with automatic fire doors to isolate the fire and extinguish it, or at least keep it under control until the fire service arrives. This solution was used in the treasury at Lincoln Castle, home of a priceless copy of the Magna Carta, where an Advanced fire panel has been combined with an extinguishant control panel and fire suppression gas to protect the vault. Automatic door controls isolate the space, preventing the fire from spreading and ensuring that the gas is concentrated in the necessary area.
Escape routes longer than normally permitted are a frequent problem in historic properties, especially where they have a residential use, e.g. as hotels or apartments. Solutions are available, through cause and effect, to control the staged evacuation of the building, verify that the alert is genuine and, if necessary, signpost a safe escape route using intelligent emergency lighting systems. Automated paging systems are also useful in buildings of this type, and pagers with flashing lights or a vibrating function can ensure that occupants with visual or hearing impairment are made aware of a fire incident.
In all modern fire situations, human intervention is crucial to avoid false alarm incidents and oversee a successful evacuation. Given the added complications of historic sites, the role of onsite personnel can be even more vital and good communication can make all the difference in averting disaster. Remote paging systems, such as the one used in London’s Royal Albert Hall, can alert staff as soon as an incident occurs, giving them the chance to access the system on their handheld device or go to the nearest panel.
Once aware, staff can access the nearest fire panel or repeater to determine the nature and validity of the incident, before conducting an orderly evacuation as efficiently as possible. Where relevant, such as in the kitchen area of a residential unit, it’s also possible to build in a short (30 second) delay for staff or trained residents to confirm the alert is genuine. This is just one example of how cause and effect programming can be useful.
Fire systems in historic buildings are often connected to an alarm receiving centre (ARC) to ensure the fire service is on site as soon as possible. Some require human confirmation of a fire and cloud monitoring means that key information can be accessed from any location using a PC or handheld device, which is particularly beneficial in locations where staff may be away from the source of the alert.
All staff should be trained to operate and monitor the fire system, with regular update sessions and fire drills to ensure the effectiveness of the procedures put in place. This is even more important in historic buildings, where evacuation routes are likely to be longer and more complex than in more modern premises. The monitoring and evacuation process can be further aided by custom interfaces, such as a 3D plan or map on a touchscreen panel, to help staff pinpoint and verify the fire incident.
Historic buildings have always presented a challenge for effective fire monitoring, detection and evaluation, but as with all fire systems, continual developments in the technology available have driven major improvements in this area.
A well-planned system can safeguard any historic site, as well as the people and treasures it contains, facilitating rapid evacuation and ensuring that fires are contained and extinguished as rapidly as possible.
For more information, go to www.advancedco.com