How fire scientists see through flames

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Researchers have figured out how to see through flames: it just takes blue LED theater lights, a camera filter, and a research facility where you can light test buildings on fire.

The scientists tasked with understanding how fire destroys structures and devours our possessions need to watch these things burn — in the laboratory, that is. This research is key for keeping people safe, but it’s not easy: there’s soot, there’s smoke, and there are the flames to contend with. The smoke and soot are easier to deal with: researchers can use less smoky fuels like natural gas when they test how things hold up to fire. Now, research published in the journal Fire Technology gives scientists a way to see through the flames, too — by shining blue light on them.


Photo by the National Fire Research Laboratory/NIST

In the past, fire researchers have had to settle for taking measurements before and after burning a test building, says Matthew Hoehler, a researcher at the National Institute of Standards and Technology and a co-author on the study. Then, they’d model the different ways the inferno could have progressed — but they didn’t know for certain what actually happened. “You might see in the end that part of the building has collapsed, but it’s much more useful to know how exactly that collapse came to be,” he says.

The problem is that most tools and sensors don’t work when they are on fire. And even from a distance, cameras don’t really work, either: the flames drown out the rest of the image. “We can’t see inside the fire because everything looks red,” Hoehler says. You can use a camera filter that subtracts out all the red wavelengths of light — which helps, but it’s not enough to get a clear view. “Your images just look blue and very dark, because it’s only picking up the reflected light,” Hoehler says. “So to bump up that signal, we add a lot more light” Specifically, blue light.


Graphic created by N. Hanacek/NIST based on a concept by M. Hoehler/NIST

Blue lights have been used before to get a clearer view of red-hot materials. But this is the first time someone has used this strategy to see through actual flames, Hoehler says: “And it turned out to work.” Now, researchers are using this technique to figure out how building materials char and warp as they burn. But Hoehler cautions — people shouldn’t try this at home. Apart from the whole fire part, the intense blue lights might also be dangerous to the eyes.

“We want to improve safety in fire, and we want to reduce the loss of life in fire,” Hoehler says. And this new technique, he says, “I think it’s been an eye-opener.”



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