Fire protection and the environment
It would be easy to assume that there is little connection between providing effective fire protection and safeguarding the environment, but that assumption would be very wrong as Don Scott, Fire Engineering Consultant with Siemens Building Technologies Fire Safety, explains.
Think first of all about fires. They almost always involve the burning of carbon-based substances such as wood, plastic, paper or fuels. It’s not surprising therefore, that the burning process produces carbon dioxide, one of the best known of the greenhouse gases. And big fires, such as a major building fire, produce very large quantities of carbon dioxide.
It’s clear, therefore, that fires are inherently damaging to the environment, which is a very good reason (alongside the imperatives of protecting life and property) for implementing effective fire detection and protection measures. After all, if a small fire can be detected and extinguished before it has time to grow, its impact, in terms of both direct damage and environmental damage, will be minimised.
To achieve effective fire protection, sensitive detectors that react quickly to fires must be used. That’s an easy statement to make but one that’s not quite so easy to put into practice, especially when environmental concerns are taken into account. One reason is that many popular types of smoke detector rely for their operation on the inclusion of a tiny radioactive source – Americium 241 to be precise.
In many circumstances, detectors of this type are capable of doing a good job, but there are growing concerns about that radioactive source. Americium 241 is currently classified as relatively safe but no one will be too surprised if that changes in future, as it did, for example, with asbestos. If this should happen, companies that have installed this type of detector may find themselves faced with an urgent, costly and inconvenient replacement programme.
Then there’s the question of disposal of the detectors at the end of their working lives. Americium 241 has a half-life of 432 years so after, say, twenty years of service, the potency of the source in a detector will have diminished by a negligible amount. Disposal of scrap detectors will, therefore, inevitably have a negative impact on the environment. Not only that, disposal is an expensive task that can only be handled by specialists. The detectors may be cheap to buy, but they’re going to be expensive to get rid of!
For these very good reasons, most businesses and public authorities no longer allow detectors of this type to be used for new installations, although they are still widely sold in DIY outlets for use by homeowners. But if these detectors are no longer acceptable for use in business and public buildings, what is the alternative?
Let’s not beat about the bush – fire detectors that don’t use a radioactive source have been available for decades. Many use some form of optical detection that relies on the scattering of a light beam from a transmitter onto a receiver due to the entry of smoke into the sensing chamber. So far so good, but these simple detectors have a significant failing: if they are sensitive enough to react quickly to a fire, they will also be prone to producing false alarms.
These false alarms might be triggered by, for example, steam from an electric kettle or a shower, or by the tiny amount of smoke produced by a cigarette or the use of a frying pan or a toaster. Of course, the fire protection industry has worked hard to address this problem not least by introducing multi-criteria detectors. These typically look not only for smoke but also for a rapid rise in temperature before they trigger an alarm.
These devices are much better at discriminating against false alarms than the simple single-sensor detectors, but they’re still far from perfect. If confirmation of this is required, it’s worth noting that the ratio of false alarms to real fires in the UK is currently around 18:1, so there’s still plenty of room for improvement. False alarms are clearly a big problem for the Fire Brigade, as they tie up skilled personnel and fire engines that may be needed to deal with real fires, but what’s the environmental connection?
To answer this question, first consider what happens when the Fire Brigade receives a false alarm. In most cases, one or more fire engines will be despatched and the exhaust fumes created during their unnecessary journeys will undoubtedly have an impact on the environment. This may seem an insignificant effect, but remember that ratio – 18 false alarms and, therefore, 18 wasted journeys for every real fire.
In many cases, there’s worse to come. In industry, for example, a false fire alarm may lead to process lines being shutdown and a large amount of energy, not to mention effort, is likely to be needed to restart them. And all of that energy is being expended unnecessarily simply because a detector generated a false alarm.
Fortunately, the most recent developments in fire detection technology are providing an effective solution to the conundrum of achieving fast responding sensitive fire detection with almost complete freedom from false alarms. In some ways, the new detectors are a development of the older multi-criteria types, in that they incorporate several sensors.
These sensors might, for example, look at not only the light transmission properties of any smoke or vapour that enters the detector, but also at how much light it scatters back toward the source. Typically the new detectors will also incorporate heat sensors that monitor temperature and rate of change of temperature. But it’s what they do with the information provided by these sensors that makes them so different from their predecessors.
The new detectors take full advantage of modern microprocessor technology – they incorporate chips that only a few years ago would have been more powerful than the average desktop computer. This means that they have the ability to use very sophisticated algorithms to evaluate the information provided by the sensors and also to compensate automatically for slow environmental changes such as the gradual build up of dirt on the detector over its working life.
In effect, the new detectors automatically and continuously perform risk assessments on the fire situation. They can, therefore, do things that would be impossible for less sophisticated units, like delaying initial reaction to a small waste bin fire on the basis that it will probably self extinguish, but providing an instant reaction if that same fire suddenly becomes more serious. In this way, these detectors can combine high sensitivity and fast response to real fires with almost complete freedom from false alarms.
In fact, so confident is Siemens, the pioneer of this new generation of detectors, in the performance of its Sinteso range that it offers its unique GAFA (guarantee against false alarms). This says that, if a properly installed and maintained Sinteso detector produces a false alarm that results in attendance by the Fire Brigade, Siemens will offer financial compensation.
As we established earlier in this article, fires have a large and detrimental impact on the environment, as do false alarms. The solution to both problems is reliable, effective detectors that do not rely on radioactivity for their operation. Such detectors are now readily available, and must surely be the preferred choice for all new projects, in order not only to protect life and property, but also to safeguard the environment.