How Does Thermal Imaging Work ?
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All objects have a certain temperature and emit waves of thermal energy
called infrared radiation. The hotter an object, the more energy waves
are emitted. A thermal imaging device translates these energy waves into
a view-able image to display a black and white “picture” of a scene. On
the screen of a thermal imager, hottest objects show as white, coolest
objects show as black, and features of other objects show as varying shades
of gray. The “thermal picture” enables firefighters to see through smoke,
find fires, identify victims, etc.
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Thermal imagers cannot see through walls, glass or other solid objects,
but they can detect heat that has transferred to the surface of an object.
The user can observe as little as a .05 ° C difference in surface temperature.
For example, from the outside of a container full of liquid, the thermal
imager operator can often see a line where the liquid ends and the dead
air space begins. Using this technology, firefighters can see heat signatures
as small as that of footprints or handprints.
Thermal Imaging Studies
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In February 1999 issue of Fire-Rescue Magazine, the editor sited a nationwide
study of the effectiveness of thermal imagers, carried out in 60 test burns
around the country. Without a thermal imager: 1) 60 percent of the time,
firefighters were unable to locate the victim and 2) more than 30 percent
of the time, firefighters couldn’t find their way out of the burning house.
With a thermal imager, 1) 99 percent of the time, firefighters were able
to locate the victim, and 2) 100 percent of the time, firefighters found
their way out of the burning house. The time required to satisfactorily
complete a search with a thermal imager dropped by 75 percent.
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The August/September 2001 issue of Advanced Rescue Technology included
an article about a thermal imaging study conducted by the Johnson City
Fire Bureau in Johnson City, Tennessee. Their research found that a victim
search without a thermal imager took eight minutes, 38 seconds. With a
thermal imager, the same victim search took three minutes, 30 seconds.
Use of the thermal imager resulted in an increase of nearly 60 percent
in search efficiency.
What are Some Ways Firefighters Use Thermal Imaging ?
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Firefighter Safety – Thermal imagers enable fire officials to identify
hazards, manage personnel accountability, identify emergency egress
points and evaluate structural integrity.
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Sizeup – Thermal imagers allow firefighters to find the source of the
fire quickly, helping them save lives and limit property damage.
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Fire Attack – Thermal imagers help incident commanders intelligently
allocate resources at a fire and to quickly get water on the fire, not
just on the smoke.
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Search and Rescue – Without thermal imagers, firefighters crawl through
burning buildings, groping in blinding smoke for unconscious victims. With
thermal imagers, firefighters can scan a room in seconds.
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Ventilation – Firefighters can safely identify areas of extreme heat,
so they can be ventilated, reducing the chances of backdraft or flashover.
Windows and doors can also be quickly identified in zero visibility, allowing
firefighters to quickly vent a structure as they move through it.
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Overhaul – After the fire has been put out, firefighters can scan the
fireground in seconds to locate hot spots that might re-ignite. Using a
thermal imager, overhaul can be done in 75% less time.
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Training – Using transmitter systems, incident commanders can observe
in real time and videotape at the scene. Videotapes can be used for review
and teaching later.
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HazMat – Firefighters can identify sources and movement of contaminants
and determine liquid levels in containers. This helps them
to manage hazardous materials spills and other incidents more effectively.
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Wildland Firefighting – Using thermal imagers, firefighters can quickly
scan large areas for hot spots, aiding them in getting the fire under control
quickly.
Development of Thermal Imaging
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Three types of technology are used in today’s thermal imagers: BST technology,
and ASI and Vox Microbolometer technology. Both technologies were developed
at the same time under a classified military program, aiming to enable
soldiers to better visualize the battlefield.
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The current technologies provide vastly improved performance over earlier
generation devices. Due to reduced size and lowered cost, these newer devices
have become available for use in a range of applications, including police
suspect searches, medical burn evaluations and a variety of applications
within the fire industry (see above).
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