Thermal Imaging Fact Sheet
How Does Thermal Imaging Work ?
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.
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
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.
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?
Firefighter Safety – Thermal imagers enable fire officials to identify hazards, manage personnel accountability, identify emergency egress points and evaluate structural integrity.
Sizeup – Thermal imagers allow firefighters to find the source of the fire quickly, helping them save lives and limit property damage.
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.
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.
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.
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.
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.
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.
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
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.
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).