To supply its customers with sophisticated, reliable and deception-proof fire detectors, Siemens Building Technologies Division operates a number of fire rooms at its headquarters in Zug, Switzerland. Because of new construction on the HQ campus, a new fire lab was placed in operation at the beginning of this year. Fire tests are conducted in a large and a small fire room under various ambient conditions. Grouped around the large fire room are a number of highly specialized laboratories where research related to individual fire criteria such as smoke, heat, gas and optics is performed. Other facilities, such as the MegaFoot lab for testing large, networked systems, complement the physical labs.
500 m³ fire room
The core of the laboratory cluster is the large fire room, a massive concrete space of impressive exterior dimensions: 12 meters long, 8 meters wide and 8 meters high, it offers 500 cubic meters of usable capacity. Its white-tiled walls are more reminiscent of an operating room, and it has very specific requirements. Filtered air is piped in and out, for example, so fire tests can be conducted under uniform ambient conditions. With the door closed, and depending on how the ventilation dampers are set, the room is completely sealed. “When we test a smoldering fire in the center of the room, we must be able to measure it reproducibly within a three-meter circle on the ceiling," explains Urs Schmid, the fire lab director. “Different surface temperatures would cause undesired airflows in the fire room. That is why the walls, floor and ceiling are controlled for differences of less than 0.1°C. Embedded water lines totaling over 2,300 meters in length ensure a uniform temperature. Heat, smoke particles, combustion gases and flames should spread reproducibly without disruptive airflows in the room, and especially at the ceiling, to allow reliable and differentiated measurement of individual phenomena. “Reproducible physical combustion phenomena are essential for the development of a fire detector’s design and sensors,” explains Schmid.
Besides ease of temperature regulation of the room’s shell, the water lines have another benefit. After a high-energy test fire, the room can be cooled quickly to its starting temperature, which allows not only more accurate measurements but also faster speeds.
Manifold reasons for fire tests
Tests must be fast-paced to keep up with the high demand. A completely new detector naturally requires multiple rounds of testing during its development. Even a new detection algorithm, a new sensor element or a different type of plastic for the optics chamber must be thoroughly tested. A change in supplier requires extensive testing as well. Building Technologies not only conducts qualification tests of new detectors in the fire lab, changes to existing detectors are also reviewed.
Siemens tests its new fire detectors in the large fire room according to the specifications defined in the applicable standards. A variety of materials – wood, plastics, liquids, textiles, cables and paper – are burned or smoldered in a number of different processes. These tests help with the development of the products, their design as well as the algorithms that detect and report a fire or differentiate deceptive phenomena. Not only does Siemens need to precisely detect hazards such as gas, heat, smoke and flames as early as possible over a certain period of time, but also accurately differentiate them in total and in combination as well as calculate them intelligently. Deceptive phenomena such as dust, steam, welding emissions, dry-ice fog and engine exhaust need to be correctly identified by the detector and differentiated from fire alarm criteria. That is why deceptive phenomena tests are conducted in addition to the test fires required by the standards using the materials mentioned.
Testing well beyond what is required by the standards
“The requirements defined in the standards are not sufficient for us,” underscores Urs Schmid, “because we assume full responsibility for the quality and functionality of the products we make and sell. A standard does not assume any responsibility.” Therefore, the large fire room is augmented by a smaller 30 m3 room where fire tests can be carried out at starting temperatures from -30°C to +70°C. Only with such extreme tests, which are not required by any standard, can Siemens ensure that its detectors will function reliably and as expected at all times.
Moreover, the fire detectors are subjected to extremely rigorous types of tests. In addition to the usual long-term climate stress tests at high temperature and humidity, mechanical tests are also performed. A vibration test that shakes the detector over all three axes for a longer period of time, for example, examines how it responds and if it is able to consistently maintain proper functionality. Additionally, more severe vibration tests are conducted on detectors to be used in aircraft or on ships. Impact and shock resistance are tested in a pneumatic machine as well as using a sledgehammer.
Other highly specialized laboratories, each focused on an individual fire characteristic, augment the two fire rooms.
Further development and testing on fire detector sensors is done in the optics laboratory. The radiation characteristic, wavelength, scattering angle and polarization are the main factors that determine detection properties. Alarm devices such as strobe lights are also tested here for light intensity and emission. The signaling range is subject to the requirements defined in the applicable standards.
Smoke and aerosol laboratories
Smoke is the most important field of testing. This also applies to the investigation of deceptive phenomena. The fire lab has multiple combined smoke and heat ducts, smoke boxes and a dust duct. Besides testing the precise response values, differentiated signal analysis of deceptive phenomena such as steam, exhaust gas and dust is also performed. The climatic chambers also located in this area are used to prepare materials for use in fire tests in the fire room, such as conditioning wood and fuses to the specified moisture content.
The gas laboratory with its exhaust fume hood most resembles a traditional laboratory. Standardized as well as R&D test using gases are conducted in compliance with current safety guidelines. Combustion gas cocktails of up to 16 different gases can be prepared to efficiently qualify new types of sensors.
The gas laboratory infrastructure is used almost daily to support ongoing production. Samples from comfort sensors (for humidity, volatile organic compounds and CO2), and CO sensors used in multi-criteria fire detectors, are regularly measured with laboratory accuracy.
A real-time gas sampling system with FTIR (Fourier transform infrared spectroscopy) to collect combustion gases from actual fires enables simultaneous measurements in the large fire lab, combined with other detection principles.
The MegaFoot lab was established to meet the requirements of major customers. It is used to test the behavior of large, networked installations of up to 64 fire control panels, such as those used in universities, hospitals or large company campuses. These systems centrally monitor and manage fire safety in many different buildings, which are often quite far apart. The installation allows the configuration of different network topologies with up to 40,000 simulated fire detectors. This makes it possible to test the communication between the fire control panels and the management stations. Right now, for example, the MegaFoot lab is configured to test the fire safety system of a power plant, and in three weeks the same facility will simulate the security system of the metro in a large city.
Realism is key
“We conduct several thousand tests in our fire lab every year,” explains Urs Schmid. “Many of them are specified by the numerous standards. We repeat some tests several times because the various standards (EN, UL, GB, etc.) require different test conditions. However, we do run additional tests of our own to allow us to take full responsibility for our products, as I mentioned earlier.” The focus is not only on different flammable materials and detector types but also on realism. Will a fire detector be used in a tunnel, a data center or a kitchen where the chef is preparing a flambé? These scenarios produce completely different physical signals that can be reliably reproduced and verified only in real-world tests that comply with the standards. “Nothing comes closer to reality than our fire laboratories,” says Schmid. “And there is no better proof than our detectors, which function as expected – robustly, reliably and immune to deceptive phenomena – day after day all over the world.”
For further information on the Building Technologies Division, please see www.siemens.com/buildingtechnologies
For further information on fire safety from Siemens, please see www.siemens.com/firesafety