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Signal Processing and the Structural Fire Safety Field

The National Fire Protection Association (NFPA) has tabulated the results from the 2017 National Fire Experience Survey with the conclusion that more than 1.3 million fires occurred last year, which caused 3,400 civilian deaths and $23 billion loss in property. While the number of fires reported are down by 2 percent since 2016, fire remains a particularly dangerous threat for which we must be vigilant.

The amount of structure fires has been decreasing in trend over the last 40 years, but they are still a prevalent danger. In 2017 it estimated there were 379,000 residential structure fires, the majority of which occurred in one- and two-family homes.  Fire is one of the most severe environmental hazards for a building, making structure fire safety vital to its the design and maintenance. There is a need for significant research in the structural fire safety field, in particular the development of sensor technology that can lead to a better understanding of the behavior of materials and structures in a fire.

Signals through the Flames

Researchers at NIST have teamed up with the University of Colorado Boulder to investigate the use of frequency-modulated continuous-wave (FMCW) Laser Detection and Ranging (LADAR) to precisely image entities concealed behind the flames, tracking the deformation of these objects. Their goal is to research fire’s effects on buildings and determine the need for further research, technology, and regulation that would increase structure performance in a fire.

The sub-millimeter precision required for a system to effectively record distortion of objects within a fire, while operating at the necessary speed to catch the event and remaining a reasonable distance away from the fire, is a feat that before now has not been achieved. FMCW LADAR, however, has sufficient speed and precision to actually quantify the deformation and movement of objects in fires at large standoff distances. It incorporates heterodyne detection, a detection method which was initially created for the field of microwaves and is not sensitive to the presence of radiation from the fire.

The Effects of the Flame on the Sensor

An important consideration in this research is the effects of the fire on the sensor and its ability to properly measure what is called the 3D point cloud. This 3D point cloud is obtained when the LADAR beam is swept across the object, through the flames, using a fast-steering mirror. The flame can affect the system’s capability for obtaining the 3D point cloud by deflecting the beam, increasing variation of range measurements due to gas refractive index changes, and scattering or attenuating laser light via the resulting soot.

Surprisingly, researchers have found that these effects were negligible at the size of flame investigated. Though they found that there can be an increase in ranging uncertainty due to beam deflections, even in the presence of acetylene flame which produces a lot of soot, the range precision can be as small as 30 µm. It is clear that FMCW LADAR shows a lot of promise for future research into the structural fire safety field. As we begin to see more through the flames, perhaps our vision for safer buildings can become a reality.

When it comes to loss of life and property from fire, any loss is too much. It becomes increasingly important, especially in light of recent wildfire-related tragedies, to continue to research the effects of fire on structures in order to identify where improvements can be made.  Sensor development and signal processing developments are being fully exploited in so many other industries, why not use this technology to help make more resilient structures? Fire season is now a year-round reality and architects will need to adapt in their design and construction accordingly.

Here at Rock West, we realize that before you can truly solve a problem, you have to understand it completely. We are committed to helping our clients utilize sensor and data processing capabilities to both identify and resolve difficulties. The world is a constantly changing place, let us use our expertise to help you adapt as well.

Sources:

  1. https://www.nfpa.org/News-and-Research/Publications/NFPA-Journal/2018/September-October-2018/Features/2017-US-Fire-Loss-Report
  2. https://www.osapublishing.org/optica/abstract.cfm?uri=optica-5-8-988