Emberometer Gauges Threat of Wildfire-Spreading Embers

The emberometer made short work of the initial experiments, some of which tested the device’s ability to track burning wooden sticks fastened to the end of a rotating metal arm, and to estimate the sizes of small plastic spheres the researchers dropped in front of the cameras, Bouvet said. With the simple tests behind them, the researchers’ next move was to find out if the device could put numbers to real embers.

In NIST’s National Fire Research Laboratory — a space where experiments involving intense flames can be carried out safely — the authors set up the emberometer downwind of a firebrand generator capable of producing showers of embers at a larger scale.

In less than a minute, the emberometer observed hundreds of embers zip by at speeds varying from tens to hundreds of centimeters per second. The tool tracked the moving particles and reproduced their forms in 3D, as before. The researchers checked the emberometer’s sizing work by collecting embers that had fallen into water-filled pans during the experiment and comparing the doused pieces of wood to their digital counterparts.

“The emberometer compares very well to what is directly being collected in the water pans,” said Bouvet. “I’m very confident for the tracking, and for the sizing we’re satisfied.”

Because of the amount and complexity of data captured by the emberometer, comparing different ember exposures could be a challenge, even if the data is accurate. The researchers’ solution is a visual aid called a firebrand rose, which summarizes the traits of an exposure by packaging information on the number and orientation of embers through space and time into one graph.

The potential benefits of the emberometer are multifold. Engineers could add depth to the shallow pool of data on real ember exposures by taking the tool outdoors and also use it to ensure that embers produced in the lab match field measurements.

Ultimately, ember exposures more true to life could lead to better research into ember-proof materials, potentially leading to better protection for structures during wildfires.

More outdoor research could make mitigation efforts more cost-effective as well, if researchers using emberometers tie ember threat levels to environmental conditions, such as the intensity of drought or wind. That data could inform new building codes and standards that offer fire safety professionals guidance on selecting a degree of protection appropriate for the surrounding conditions.

“We want to be able to look at the fuel type, topography and weather, and have an idea of how serious an ember exposure might be for a structure,” Bouvet said. “Building codes can use that information to advise you on how to harden your structure. If you’re somewhere in the middle of a grass field, it’s not going to be the same as if you’re surrounded by tall trees.”

The NIST team’s next step is to give its system a touch of artificial intelligence. Because the device only has four eyes, it cannot always make out every detail of an object’s shape. But with machine learning, the emberometer could fill in blind spots, improving its size reconstruction measurements.

Soon after, the researchers plan to test-drive the emberometer in the great outdoors, where it can face embers born out of real — albeit controlled — wildland fires. By learning lessons in the field, the team could further tighten its design, readying the emberometer for widespread use.