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Wildfire terminology, explained

Wildfire smoke rises from the landscape.
Wikimedia Commons
Wildfire smoke as seen from the International Space Station.

The heart of wildfire season is right around the corner. Each year when we provide you with information about wildfires in our region, we use terminology such as containment percentages, or we let you know when crews are “mopping up” a fire.

To help us get a better sense of what those and other fire-related terms really mean, KLCC’s Love Cross invited Kevin Reese, the Fire Staff Officer for Northwest Oregon Interagency Fire Management, to break them down for us.

She started by asking him to first break down what it means when there are warnings for “fire weather.”

Kevin Reese: Weather is the most dynamic influencer of fire behavior. And the primary concerns that we watch are wind and relative humidity. There are a couple other variables to that, but at its base function, wind is the driver of fire spread and then relative humidity and the reduction of moisture in the atmosphere and in live foliage to increase the chance of combustion or the rate that it does combust.

Love Cross: And when crews are on a fire, we hear the terms fuel break or fire break. Can you break that down for us?

Reese: Fuel break is a pre-made strategic reduction in fuel usually along roads, usually along ridges waterways where it's a natural feature that can strategically slow down or stop fire and then we will reduce fuel loading, cutting brush, removing dead and down material, sometimes removing trees if necessary to reduce the amount of fuel that fire can burn through. Just strengthening that strategic feature. Sometimes firebreak can be the fuel break like I said or sometimes firebreak can be a suppression line or a containment line and that can be much smaller if it's hand line, maybe that's a 10 to 15 ft socket, removing all of the vegetation within that 10 ft 15 ft swath and then a scrape or digging down to mineral soil through the duff and sticks and vegetation. And that's usually 1 foot wide, 2 feet wide, depending sometimes a little bit larger based on equipment.

Cross: And then as crews gain ground on fires, we hear about containment- us here in the media report percentages of containment. How is that determined? And what does it really mean?

Reese: Containment is the physical containment line that is secured around the fire. So, you'll hear a lot of times “The Smokey Bear fire is 60% contained.” So, that means that they have 60% of that fire contained either with handline, either with dozer line, whether they fired up around it and that's secure black. Black being burned fuel that's no longer posing a threat for fire spread and they feel secure- they being the instant commander or the incident management team feels secure about that section of line. Now, sometimes they might have more line around it. They might have a line completely around, but they're not calling it that because the line hasn't been secured. It hasn't been mopped-up where crews, engines, resources are in spraying water, stirring up hot spots, putting all of the still burning embers and small little flame pockets out so that the likelihood of that escaping over the line is decreased after it's secured, mopped-up 100, 200, 300 feet in, to lessen that chance.

Cross: And I think you just broke down what mop up means, but that is one of the other terms that we do use as fires are kind of on the downward slide, “mop-up.”

Reese: Mop-up is really the securing of the lines. So, the initial part of our suppression is getting a hose lay in or getting handline in if equipment is available, using equipment to put in direct lines going as close to the fire as we can and, and trying to get that fuel and vegetation reduced adjacent to the fire, getting a line that's down to mineral soil so that the fire won't burn across it and trying to get around it. The next step is securing that line and, and mop-up is our primary way to do that. And that's just making sure that, that there's no more heat adjacent to that control line.

Love Cross joined KLCC in 2017. She began her public radio career as a graduate student, serving as Morning Edition Host for Boise State Public Radio in the late 1990s. She earned her undergraduate degree in Rhetoric and Communication from University of California at Davis, and her Master’s Degree from Boise State University. In addition to her work in public radio, Love teaches college-level courses in Communication and Sociology.