This feature explores the potentially significant impact of poor system survivability, why survivability should be a shared responsibility and the factors that need to be taken into consideration to ensure it.
The term ‘survivability’, when used in the context of fire and life safety systems, relates to the ability of the entire fire detection and alarm system (FDAS) to perform properly and remain fully operational while under attack by fire.
Some fire detection and alarm systems only need to initiate an alarm if a suspected fire is found, but when systems require a phased or complex evacuation, the FDAS needs to be able to continue working while the fire is taking place as this will ensure that the fire management authorities can establish the location of the fire and monitor its spread. This information is essential to ensure a safe and controlled evacuation. If a FDAS is badly designed, it could fail relatively quickly. Premature failure of a FDAS could be catastrophic as vital information will not be provided to the fire and rescue services.
Failure in one area due to poor survivability could result in the system being unable to activate audible and visual alarms to warn people of the imminent danger. In the case of a phased evacuation, the system might be incapable of further evacuating another alarm zone area where the fire is spreading to. For example, if all the detection control panels are located in one area and there is a fire in that area, the entire system would be wiped out in a matter of seconds.
The need for an industry-wide collaborative approach
Although a number of industry standards relating to survivability already exist, each has a specific focus and there is no single piece of regulation which stipulates the need for the overall survivability of a FDAS.
FDAS survivability should be a shared responsibility and achieving survivability – and greater awareness of its importance – will require an industry-wide collaborative approach. There are several standards that touch on survivability – including BS7975, BS8629, BS 5839 and BS 8519 – but the real-life understanding of the implications of these standards varies considerably and there is no clear industry performance specification for FDAS survivability.
How the standards are actually achieved comes down to the design, installation and system commissioning process. And this is the root of the problem. Many different factors determine the survivability of a FDAS and unless it has been designed with survivability in mind from the outset – and each individual element of the system is capable of surviving for the length of time required by the building and its evacuation strategy – the risk of system failure is high. Engineers have to understand the fire risks associated with the whole system to ensure continued fire/evacuation strategy and system design compliance.
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The need for education around building use and survival times
The foundations for improving the survivability of fire detection and alarm systems are already there thanks to the existing regulations. However, rather than introducing more regulation, the emphasis now needs to shift onto education and raising awareness across the sector of why survivability is such an essential consideration when designing FDASs.
There is a lack of industry understanding about the length of time systems should be able to survive for. Specifiers need to fully understand the intended use of the building and its detailed fire/evacuation strategy. The survival time of fire alarm/firefighting systems must also be specified.
It is often assumed that the different elements of the FDAS only need to survive for 30 minutes before they can fail, but this is not long enough in complex buildings such as large residential buildings, offices, shopping malls, airports and hospitals. Complex buildings must be actively assessed as a single, coherent system of interdependent components. In these types of buildings, the design and the connectivity of a FDAS and the building’s evacuation system must last much longer than 30 minutes.
BS 8519 takes into account the need for different survival times of fire-resistant cables and recognises three fire survival times according to the specific life safety or firefighting application:
- Category 1 – 30-minute fire survival time
- Category 2 – 60-minute fire survival time
- Category 3 – 120-minute fire survival time
If these category times are specified for cables on a project, for example, then the design of the whole FDAS must follow the same survival time criteria to ensure the entire system is capable of lasting that long. This requires careful consideration of which fire detection and alarm equipment to use, where to locate the equipment and where the equipment is controlled from so that it does not fail early and therefore negatively impact on the required fire survival time of the cables.
While design expertise is required for complex buildings to ensure adequate system operation and fire survivability, specifiers need to fully understand the intended use of the building and its detailed fire/evacuation strategy, engineers must understand the fire risk experienced by the whole system to ensure continued fire/evacuation strategy and system design compliance, and those responsible for procurement need to manage expectations of survivability performance.
An intrinsic approach is required to having an overall survivability time that those responsible for each element of the system should adhere to. Survivability should be a prerequisite of all complex systems, and each building needs to be assessed on a case-by-case basis. As an industry we have a shared responsibility to better understand how to deliver survivability of fire and life protecting systems during an emergency.
Adhering to Dame Judith Hackitt’s ‘golden thread’ approach
Designing fire and life safety systems to be survivable from the outset is very much in keeping with the recommendations and principles outlined by Dame Judith Hackitt in her 2018 ‘Building a Safer Future’ report which was published in the wake of the Grenfell Tower disaster. In her report, Hackitt recommends the introduction of a ‘golden thread’ approach which applies to ‘both the information that allows you to understand a building and the steps needed to keep both the building and people safe, now and in the future’.
The guidance is aimed at supporting those responsible for the design, construction and management of buildings, and Hackitt’s recommendation is for safety to be taken into account at every stage in a building’s lifecycle. We cannot risk another tragedy like Grenfell and by raising awareness of the importance of FDAS survivability and other engagement activities with our customers and industry contacts, GFE believes we are applying Hackitt’s golden thread approach to system survivability. Our aim is to help building owners to better understand their buildings and give them confidence that system survivability has been built in from the outset.
The role of advanced technology in ensuring system survivability
One way in which GFE is leading the way in system survivability is our inbuilt mesh network. We have developed our Chameleon multi-master, multi-path, peer-to-peer network, which is a fundamental departure from previous fire alarm control panel (FACP) networking arrangements in that it creates an extremely resilient infrastructure for the management and interaction between multiple FACPs in a single system. Every FACP connects directly, dynamically and non-hierarchically to all the other FACPs in the network. As a result, it contributes to extremely high resilience, particularly in complex buildings where higher levels of system survivability (BS 8519 Categories 2, 3 and above) are required for life safety and firefighting applications, including circuit integrity during a fire.
A fully closed loop and multi-path solution, the Chameleon network addresses and overcomes the limitations associated with traditional RS485 multi-drop topology. When RS485 multi-drop topology is used, there is no redundancy in the network, which means that in the event of a short circuit in the cables, for whatever reason, all interaction and communication between the different FACPs would cease because the information can only travel from node to node in a linear manner, to the left or to the right. In comparison, however, the Chameleon multi-master, multi-path, peer-to-peer network has point-to-point communication across the entire network.
Each time an event occurs, the FACP forwards that event through all network communications ports, effectively broadcasting the event across the entire network. Each node then records the event on its local event log, which has the capacity for up to 10,000 entries. Each FACP is capable of sending messages to and receiving messages from other FACPs, ensuring high network redundancy because all FACPs are interconnected. In the event of one or more FACP links going down, all the other FACPs will participate in the relay of information, so the entire network will continue working while work is undertaken to resolve the individual incident or issue with the FACP/FACPs.
Finally, as each segment of the Chameleon network is galvanically isolated from all the others, the network also has superior immunity to electrical interference, further enhancing overall FDAS survivability.
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What needs to happen now?
Unfortunately, the siloed approach taken by the sector to date has resulted in the survivability of FDASs not being given the focus it needs. So, first of all, we need to help raise awareness of the regulations that are already in place. We also need greater transparency about survivability times in performance specifications. This will ensure that survivability is achieved and will help to create a level playing field where everyone understands, expects and quotes to an agreed specification.
As a sector, we should be pushing for FDASs to be designed for survivability from the outset rather than as an afterthought. However, we also need those responsible for specifying, procuring, installing and using fire and life safety systems to have a better understanding of system survivability. Those involved at each stage in the process – from the design and specification through to the installation – should accept shared responsibility for system survivability.
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About the Author
Business Innovation Manager – EMEA at Apollo Fire Detectors.
