Down to the wireless
28 May 2022
EVER SINCE the first wireless-based detection technologies were installed more than 20 years ago, manufacturers have been innovating to convince an often sceptical audience that such systems are at least comparable, and in some ways superior, to their hardwired cousins, as Derrick Hall duly observes.
Today, wireless technology is fast becoming ubiquitous, not just in its ‘traditional’ markets, but also in much wider fire safety applications where reliability is not simply a ‘nice to have’, but rather the difference between life and death. Why, though, have wireless systems taken so long to prove themselves, and what trends are now emerging to render wireless the ‘go-to’ preferred solution in many cases?
Historically, the Achilles heel for wireless was battery life and the risk of a detector failing simply because it had lost power, while there was no way of knowing until it was too late. This led to managers having to keep logs of all detectors on site and also knowing when their batteries needed to be replaced. It was an impractical, unreliable and expensive way of doing things and, not surprisingly, led to a large amount of negative publicity.
In more recent times, battery technology has improved to such an extent that battery life itself is no longer an issue. With batteries now able to last anything from between seven and ten years, and with today’s detectors designed to consume less energy, what was once a legitimate cause for concern has apparently disappeared.
A further perceived weakness was signal reliability. Some devices failed through poor installation and others because the signal wasn’t strong enough and/or could easily drop out, thereby leaving a system vulnerable to failure. Advances in technology, and in particular the evolution of new MESH networks, have solved this issue and dramatically improved system reliability.
Modern wireless networks have redundancy built into them and actively seek the strongest signal expander should the primary signal drop out or become compromised in any way. They will continue this cascade such that it provides the signal with anything up to ten different paths, making it more reliable than most hardwired systems, which may only have two.
Ease of installation
While the weaknesses of early wireless systems may have dissuaded some installers, many more were quick to embrace the benefits that wireless technology had to offer (and still does). Unlike hardwired systems, for example, a wireless system, by definition, has no wires and is therefore much quicker and easier to install. Given that a significant amount of the cost of a new fire safety system is tied up in the installation engineer’s time on site, this represents an important saving for the end user.
The simplicity of a wireless installation has taken on even greater significance over the past two years, and especially so since the start of the pandemic. Many installers have found themselves under increased pressure to minimise their time on site to ensure only essential interaction with staff and the minimum of disruption for the host business. In an age where skilled labour is expensive and in very short supply, it’s fair to state that being able to train a new employee to install a wireless system is far easier than the myriad complexities traditionally involved with a hardwired solution.
The greatest advantage of wireless systems, though, and one that has rocketed them to the top of the charts now that the reliability issues have been overcome, is in the flexibility they afford installers specifying for those projects where cost or practicality would have previously made specific technology prohibitive. Owners of historic buildings or heritage sites, for example, tend not to take kindly to engineers being keen on drilling through walls or ceilings that may have stood for a thousand years or more simply to run a cable to/from a power source. Installing wireless detectors negates that scenario.
A good case in point is Chester Cathedral. Brad Parker, founder of Charles Thomas Heritage Fire Protection, was tasked with specifying and upgrading the fire detection alarm system previously installed. The challenges were typical of a building that can trace its roots back to 1250 when work initially began on the site of a former Benedictine Abbey. Thick stone walls and lead-lined roofs meant that Parker had to think outside the box.
“With the latest MESH technology,” noted Parker, “rather than one expander, we can have three, four or even five redundancy paths and the signal connects itself automatically to the strongest expander to create the MESH.”
Parker’s colleague, operations manager Byronn Alty, asserted: “We went to what we would believe would be the ‘dead spots’ within the structure and the device started talking to the strongest radio signal expander within its area. Looking at the drawings, we thought it would communicate with expander one, and yet the device ends up talking to expander two.”
A further benefit to the MESH technology in use, and which feeds back into the ‘ease of installation’ point mentioned earlier, is that it’s simple ‘plug and play’. “Chester Cathedral has an outbuilding with an old bell tower so there needed to be a link between that and the main structure,” explained Alty. “This was a key design challenge for us. How would we realise radio? The new wireless MESH is ‘plug and play’ and it was great to see it working. Even having used it only the once, my confidence in terms of installing, programming and commissioning is now on a high. That tells you how easy it is to use.”
The growing sophistication of wireless systems is not limited to their use in heritage sites. They’re also increasingly being deployed in more modern settings, such as hotels, hospitals and care homes: environments where detection is only one part of the story and safe evacuation is a priority.
Within the fire evacuation space, wireless systems are increasingly playing their part in the two essential calculations that installers/engineers have to make: the Available Safe Egress Time (ASET) and the Required Safe Egress Time (RSET).
ASET refers to the amount of time that elapses after the fire has ignited, but before the presence of smoke, heat and poisonous gases creates what are considered ‘untenable’ conditions. In calculating the ASET, various factors have to be considered to ‘model’ how a fire will behave. These include the building materials and the by-products of those materials when they burn (for example, the gases they emit), as well as the geometry of the space where the fire started and any physical barriers that might temporarily arrest the fire’s progression through the location.
The RSET, on the other hand, refers to the duration of time required for the safe evacuation of the occupants of a building after the fire has been signalled. The RSET is calculated as the sum of three separate components: the alarm time, the pre-movement time and the movement time.
Alarm time (also referred to as the occupant notification time) is when occupants of the building are first made aware of the fire, typically via an automatic fire alarm system. Pre-movement time, which is also referred to as evacuation delay time, is the time it takes for an individual to start moving upon hearing an alarm. This takes into account many different factors, among them the delay in deciding whether the need to evacuate is genuine or not – a delay that can last anything from a few seconds to a handful of minutes depending on the type of building involved and the occupants within.
The third element, namely movement time, is the time it takes an occupant to move to a position of safety and accounts for flow rates through applicable exits (remembering that, in many larger buildings, evacuations are ‘phased’ and often conducted on a floor-by-floor basis in order to prevent vital exit ways from becoming blocked).
The ASET and the RSET calculations have taken on new poignancy in recent years, especially post-Grenfell, with a particular focus on the impact of building materials. As has been widely publicised, this has realised the adoption of ‘Waking Watch’ provision as an interim – albeit very expensive – safety measure until such time that any unsafe cladding issues have been resolved.
The Government is actively encouraging the installation of fire alarms in preference to ‘Waking Watch’, which is a move supported by the National Fire Chiefs Council’s chair Mark Hardingham who has been quoted as saying that building owners “should move to install fire alarms as quickly as possible” (and notably so in those instances where installed solutions can be upgraded to a BS 8629 system focused on evacuation once remediation work is completed). This is where new trends and developments in wireless technology can play a significant role.
Of course, new wireless detection technologies – whether optical, thermal or multi-criteria in nature – are now commonplace. Their reliability has improved significantly. Some sensors now feature double dust traps in order to prevent false alarms.
The bigger issue with any fire situation is not in detecting the fire, but rather in the safe evacuation of people and affording them sufficient time to do so. The most effective evacuation solutions are those that include a voice message, but voice alone has its limitations. This is true in applications within hospitals or care homes involving more vulnerable people and where there are invariably residents who have issues with sight or hearing. Visual alarm devices have evolved for those who may not be alerted by an audible device, while ‘white noise’ technology has also been developed for the partially sighted.
The latest trend is towards solutions that take advantage of the Doppler effect (ie a change in frequency of sound such as that realised with ambulance or fire engine sirens whereby sound waves are compressed ahead of a moving source).
Technologies are emerging that take safety to another level. It might be the case that, in a fast-moving fire, one particular exit may no longer be safe. An individual could be heading towards danger rather than away from it.
Again, this is where new thinking has led to ‘smart guiding’ technology that employs sound, light and voice command functionality to provide the ultimate clarity in terms of evacuation instructions. The sound/light and voice command functions all exist in a single device that’s also a detector. Importantly, the whole solution is wireless.
Specific fire safety technologies will dip in and out of fashion. Manufacturers will claim different capabilities for their system over another, while installers will continue to favour products with which they’re most familiar and balance ease of installation with delivering an effective and reliable solution that meets – and even exceeds – their customers’ needs.
For installers and end users who have yet to fully embrace exactly what today’s wireless technologies can really achieve, perhaps now is the time for them to make a detailed assessment.
Derrick Hall is Director of Sales at Kentec Electronics (www.kentec.co.uk)