"It can pick up reflections from a fire off the walls, so it can directly survey a multiple-room enclosure for fire from a single location. This gives it a very fast response time compared to a smoke detector, which doesn't go off until smoke has traveled to it -- a delay that can be several minutes." Because the new detector is very sensitive, Gore says, it may first be used in large warehouses, but it also will benefit the home.
Gore and Yudaya Sivathanu, a Purdue research scientist, developed the new detector with the help of a two-year research grant from the Center for Fire Research at the National Institute of Standards and Technology (NIST).
Because the new device uses fiber optics to detect radiation from a fire, optical fibers could easily be run from a central detection unit to each room in a multistory building, Gore says, providing "blanket" coverage.
The prototype detector is bulky, but Sivathanu has established a small business, En'Urga Inc., at Purdue's Business and Technology Center to develop the detector for industrial and commercial use within the next three to five years. Sivathanu presented information on the new detector Aug. 15 at the Second International Conference on Fire Research and Engineering in Gaithersburg, Md.
The device, which detects the characteristic light given off by an uncontrolled flame, could be hooked into a telephone or personal computer to automatically notify the fire department and give off audio safety instructions when a fire starts, Gore says.
"I believe that in the next few years, the home PC will control the home security and safety systems and that a fiber optic communication network will carry such signals in addition to voice and data. This detector could be easily integrated into such a communications network."
The wavelengths of light that the detector picks up are in the near infrared -- in other words, heat. "The idea of using heat to detect fires is not new, but we have applied a unique discrimination algorithm to the process to eliminate false alarms," says Gore, whose previous research on different types of flames helped NIST researchers in their analysis of oil well fires in Kuwait.
Over the past two years, as they were developing the detector, Sivathanu, Gore and their graduate students examined the near-infrared radiation given off by several "standard" types of fires. These type of fires cover a wide range of combustible materials.
"We have analyzed flames based on the way the intensity of the light fluctuates as they burn," Gore explains. "For example, we may see a peak in intensity every tenth of a second, and then the pattern is repeated. That type of fluctuation frequency is characteristic of an uncontrolled fire."
Once a flame has been detected, a sophisticated computer program analyzes the fluctuations in its near-infrared intensity -- its so-called infrared signature -- and determines whether to sound an alarm. While infrared signature analysis has been used by the military in a variety of ways, using it for fire detection is a new application.
"We have 'taught' the detector not to respond to common household flames such as candles, gas stoves and cigarette lighters," Sivathanu says. "It also does not respond to fluctuations from hot plates, solar radiation or fluorescent light, which are different than those from uncontrolled flame.
"We also installed a corrective filter when we learned that the detector went off when someone waved their hand quickly in front of a hot plate placed in direct view of the detector. We still have a problem with the alarm going off from a fireplace, which is an uncontrolled flame, but we are developing ways that may make the device 'blind' to certain spots in the room. Conventional smoke detectors also go off from smoke from fireplaces."
Another bug to be worked out of the new detector is its difficulty in picking up smoldering fires, an area where smoke detectors also are slow to respond because of the time it takes for the smoke to reach the detector.
"The intensities obtained for smoldering fires are too low for our detector to successfully discriminate them from background noise," Gore says. "However, new, more sensitive infrared technologies are now available that might boost this capability in our detector."
Sivathanu and Gore have received a new, three-year grant from NIST for research that will focus on detecting the far-infrared radiation emitted from a fire, the type of radiation associated with smoldering.
Sources: Jay Gore, (765) 494-1452; e-mail, firstname.lastname@example.org
Yudaya Sivathanu, (765) 494-9364; e-mail, email@example.com
Writer: Amanda Siegfried, (765) 494-4709; e-mail, firstname.lastname@example.org
Purdue News Service: (765) 494-2096; e-mail, email@example.com
CAPTION FOR PHOTO GORE.DETECTOR
Yudaya Sivathanu, a Purdue research scientist (right) and graduate student Andrew Lloyd are part of a team tha has developed a new type of fire detector that may one day be hooked up to a home personal computer or telephone to automatically notify the fire department when a fire is detected. The device uses fiber optics to detect the characteristic infrared radiation signature of an uncontrolled flame. (Purdue News Service Photo by Vincent Walter.)
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Jay Gore, Purdue professor of mechanical engineering (foreground) and his doctoral student Xian-Chua Zhou use a sophisticated laser technique called particle imaging velocimetry to investigate how air flows into a fire. These data are being used to better estimate how much carbon monoxide and other toxic products are emitted from a fire, information that could affect building ventilation codes and help firefighters better estimate how much of the poisonous gases are present in areas such as corridors. To measure the velocity of the air flow into the flame, the researchers artificially seed a special flame chamber with particles. When a flame is lit, the particles travel with the air into the flame. A laser, pulsing once every 150 microseconds, shines on the flame and reflects off the particles and into a camera, which records an image of the particles with each pulse. By carefully measuring the tiny distance a particle moves between laser pulses, the researchers can determine the velocity of the particle, and hence the speed of the air flow. (Purdue News Service Photos by Vincent Walter.)
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