SIEMENS

The pieces of wood on the hot metal plate are beginning to smoke, first in thin plumes, which become thicker and thicker. After three or four minutes, a column of white smoke has formed directly above the glowing wood chips.
The air in the rest of the room is clear, however — and this is how dangerous smoldering fires generally begin. The moment of truth is therefore at hand for a test involving eight different kinds of smoke detectors installed on the ceiling of the room. When will each sound an alarm? "Most major blazes begin as smoldering fires," says Markus Späni, head of Siemens Building Technologies' (BT) Fire Lab, which is located in Zug, Switzerland. "Such fires initially produce little smoke. What's more, temperatures don't rise much either." The Fire Lab is where the fire detection systems developed and tested by BT researchers and engineers are actually demonstrated.
While the wood chips continue to smoke away on the 500 °C hot plate, curves depicted on a monitor reveal which of the detectors have recognized the danger. Several of the optical detectors from Siemens have already sounded an alarm. But an ionization smoke detector — for many years the detector of choice — has yet to notice anything.
Ionization detectors use a weak radiation source to ionize the air, thus making it conductive. Air conductivity decreases if the ions collide with smoke particles, causing the detector to sound an alarm if it measures the lower current. "This system works great when there's a blazing fire — but when a substance is simply smoldering, the number of smoke particles is so low that the detector won't notice them until some time after an optical unit does," Späni explains.
On the other hand, the signals produced by the optical detectors that appear on the monitor clearly indicate the danger posed by the thin smoke at a very early stage. Detectors utilized in Siemens' new Sinteso S-Line fire protection system are particularly fast and reliable, as they are equipped with two optical sensors — rather than one, as was previously the case — and because they have two temperature sensors.
"There are no other detectors like these at the moment," says Späni. The units operate according to the principle of optical forward and back scatter. Inside each unit's housing is a kind of labyrinth with many plastic walls. The labyrinth steers the scattered light onto precise pathways. If no smoke is present, the light will hit the walls of the labyrinth, where it will be completely absorbed. If, however, the light rays encounter smoke particles, the light will be scattered and some of the rays will hit photoelectric cells integrated into the unit.
Smoldering fires produce light-colored smoke containing large particles that can be better detected through a forward scatter than a back scatter system. The exact opposite is true of open fires, which generate smaller dark particles. Here, back scatter produces a stronger signal than forward scatter. A processor in the detector analyzes all this data, calculates what type of fire is most likely occurring, and then sounds an applicable alarm.

Recognizing Harmless Smoke. The detector's ability to distinguish between types of smoke is made possible by advanced signal analysis (ASA) technology developed by Siemens. ASA software enables the processor in the detector to convert the signals recorded by the photoelectric cell and temperature sensors into mathematical values.
Specially-developed algorithms then compare the signal values with predefined value levels, and the resulting analysis allows the system to differentiate between a real fire for which an alarm needs to be triggered, and harmless steam from cooking or even smoke from welding.
"Every detector equipped with ASA technology can be precisely calibrated for the environment in which it is to be used," Späni explains. A good example of the importance of such a feature is offered by industrial applications, where harmless smoke or steam is frequently formed, and generally causes conventional detectors to trigger an alarm. "That's not the case with multi-sensor detectors equipped with ASA software," says Späni. "They recognize that smoke from welding can not be a blaze because the typical intervals of the welding process mean that the resulting smoke doesn't form continually."
To ensure such functionality, the parameter sets in the detector must be precisely aligned with the types of fires expected at a given facility, as well as with data on the activities that could trigger a false alarm. A unique feature here is the device's ability to issue alarms in stages. If the measured sensor signals do not allow for a definitive conclusion, the system nevertheless reports to the control center that a dangerous situation may be in the process of developing. "In the case of a full-fledged alarm, the system automatically contacts the fire department," says Späni.

Safer Skyscrapers. Multi-sensor detectors can do even more, however, as they are equipped with an electrochemical cell that enables them to register the presence of carbon monoxide (CO), which is invisible and odorless, and therefore especially dangerous. Just a few lung fulls of CO can kill, and carbon monoxide poisoning is the number one cause of death in fires.
Thanks to CO multi-sensor detectors and other technical features, Siemens is moving into a new dimension in fire protection for hotels, skyscrapers, and shopping malls. In fact, such facilities can no longer be safely operated without such state-of-the-art technology. As a consequence, new smoke detectors have to be integrated into high-performance safety systems. To this end, Siemens developed its Sinteso fire detection center systems, which are modularly designed and equipped with standard interfaces. These systems can be expanded at any time to accommodate new building wings or the modernization of older equipment.
The systems independently monitor all detection devices and evaluate their data. Several systems can be networked and operated either locally or via a control center. The systems also have a unique emergency backup feature, which, even in the event of a complete failure of the main processor, enable them to register and trigger any alarms initiated by a detector, notify the fire department, and take measures to ensure the evacuation of a building. This makes it possible to utilize Sinteso even in large areas such as airports and shopping centers. Europe's largest shopping mall — Westfield London — is monitored by a Sinteso system, for example.
Sinteso's modular design enables control centers to be continually updated with the latest technology, including a combination of video and fire detection systems. Video images can be very helpful in a fire — but up until recently video surveillance and smoke detection system functions were not aligned with one another. Put simply, this has meant that cameras have not been programmed to automatically record images from the area where an alarm has been sounded. With this in mind, Siemens has developed a combined system that automatically transmits live images from the areas affected by a fire, so that such images can be analyzed both immediately and later. Such images can provide valuable information on the causes of a fire as well as the real-time situation that firemen and rescue services personnel will confront at the scene.

Nitrogen-Water Mixture. Fires are usually extinguished by sprinkler systems. The idea is to cool flammable objects and prevent a blaze from spreading quickly. "This technique is not, however, suitable for facilities such as archives, museums, and libraries because water damages or destroys their valuable papers, books, and paintings," says Dr. Thomas Mann, head of the Extinguisher Competence Center at Siemens BT in Zug.
In order to avoid such consequences, an alternative method is to smother a blaze by filling the area in question with a non-flammable gas, which displaces the oxygen in the room. When the oxygen component in the air falls below a certain level, the flames automatically die out. A number of fire extinguishing systems based on natural gases function along these lines.
Siemens has come up with a solution that combines gas and water while keeping each at a minimum. And thanks to its natural constituents, the system is environmentally friendly and safe for humans. Known as the Sinorix H2O Gas extinguishing system, it uses nitrogen to lower oxygen concentrations, while at the same time emitting a mist that reduces the ambient temperature to below the flash point for objects in the room. Both extinguishing agents flow through the same pipe network and nozzles, whereby the nitrogen propels the water in a manner that ensures a consistent and moderate flow. It takes only a small amount of water to substantially cool down overheated devices or surfaces, thereby offering further protection in addition to the gas' flame-retardant effect. In addition, the mist reduces the danger of re-ignition.
If the greatest possible extinguishing effectiveness is to be achieved, the nitrogen-water mixture must be precisely aligned with the specific properties of, and the expected fire risks in, the area in question. Siemens has therefore developed a program that precisely calculates the dimensions required for the pipes and spray nozzles for diverse application areas, as well as the distances involved and the time it will take to spray specific rooms. Both the extinguishing device and the calculation program have been evaluated by the German Property Insurance Association (VdS). The result: Sinorix H2O Gas is the only combined gas-water indoor extinguishing system to be approved to date. Sinorix H2O Gas was also presented with the Security Innovation Award at the 2008 Security trade fair in Essen, Germany.
Such outstanding references played a key role in convincing safety officials at the Danish Royal Library in Copenhagen to choose Sinorix for its fire protection needs — and the protection of its valuable books and documents. "They brought some valuable historical books with them and we demonstrated how a Sinorix extinguishing procedure causes no permanent damage to them," Mann reports. In fact, the dampness of the books was so minimal that they didn't even have to be dried off.