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Embers are raining down on Australia. More than two dozen people have died in fires that have already been burning for months. Nearly 2,000 homes have been damaged or destroyed, and the burning debris means thousands more are in danger of catching fire. NPR's Rebecca Hersher reports.
REBECCA HERSHER, BYLINE: If you were trying to create a wildfire nightmare on Earth, you'd probably start with something like the situation in Australia.
DANIEL GORHAM: So what we're seeing in Australia right now, we're covering a lot of area with a lot of flame.
HERSHER: Daniel Gorham studies how homes catch fire for the Insurance Institute for Business and Home Safety.
GORHAM: Big fires have big plumes, and these big plumes actually suck in air horizontally, just like a campfire would. But a big fire draws in air very quickly horizontally, and then it goes up into the plume vertically.
HERSHER: It's enough to sweep tons of fiery debris thousands of feet up into the atmosphere. So when you see a big, smoky cloud above a fire, imagine it's full of flaming junk - embers.
GORHAM: So embers range in size from small, little particles breaking off from a burning blade of grass to pine cones. And in cases where we have really large fires, embers the size of your hand or larger than that are easily lifted up and, in those cases, travel miles ahead.
HERSHER: Miles ahead of the actual flames - so homes far away from the fire itself are being pelted with flaming bark and leaves, which, honestly, people who study wildfires used to think was kind of a sideshow. The real danger to your house, they thought, was from the heat and intensity of a wall of flames arriving in your yard. But that was wrong. Ian Weir is an architect. He's also one of the authors of Australia's national building standards for fire.
IAN WEIR: So we understand that 90% of homes are lost through embers or firebrands.
HERSHER: When he says 90% percent of homes are lost to embers, he's referring to a very specific study from 2010 by Australia's national research agency. Before that, research in the U.S. had shown that embers were responsible for a lot, probably the majority, of homes that were destroyed in California fires. But the 2010 study in Australia found that embers appeared to be, basically, the way that homes there were catching fire. But how to fix the problem? For that, Weir in his building-code colleagues in Australia looked back to research from the U.S.
WEIR: And what we've learned actually from your National Institute of Standards and Technology - they've done some great research on exactly what is the dimension of the gaps at which point we start to lose houses. And they found that anything greater than two millimeters would enable the embers that would be sufficiently large to actually ignite wall cavities and furniture and so on.
HERSHER: So in the most recent set of building standards, which were adopted in Australia just last year, new homes that are being built in fire-prone areas are required to plug up gaps in window casings and door jams and roof fence. But Weir says sealing the gaps isn't enough. Australia's building standards are not sufficient to protect against the kind of massive, endless fires it's experiencing now. One of the big problems, he says, goes back to something Australians share with many Americans - a desire to live in the woods - or as he puts it...
WEIR: Retreat to the bush - and we like to build timber homes when we're in the bush. And now we've realized, well, you know, how do we retrofit that?
HERSHER: Building codes in both Australia and the U.S. generally only apply to new buildings, and retrofitting is very expensive. So all those older, flammable homes in the bush are sitting ducks.
Rebecca Hersher, NPR News.
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