ARI SHAPIRO, HOST:
For this next story, we want you to imagine the smell of wood burning on a campfire or a wood-burning stove or even a wildfire. That smell of wood smoke is well-known. The effects it has on our health and the environment are not. With wildfires happening more often, and the climate changing, researchers are trying to understand the science behind smoke. NPR's Nathan Rott spent some time with them.
NATHAN ROTT, BYLINE: It's the first thing you notice walking into the cavernous test room at the Missoula Fire Sciences Laboratory in Missoula, Mont.
It smells like fire in here.
JIM ROBERTS: Yep.
ROTT: Though not the kind of fire you'd want to smell.
Smells like dung fire.
ROBERTS: Yeah, that was yesterday's fire. Yeah. And this one is...
EDWARD O'DONNELL: This is subalpine fir.
ROTT: Jim Roberts and Edward O'Donnell will burn 18 different mixes of fuels - or biomass - in this room, each representative of a place where fires burn - a chaparral mix for southern California, Ponderosa pine duff for forests here in Montana, even building materials and that oh-so pungent llama dung because the latter is an important fuel for heating homes in places like Nepal. Different things produce different smoke when they burn, and these researchers want to know what those differences are.
O'DONNELL: We're burning.
ROTT: O'Donnell turns the knob and within seconds...
(SOUNDBITE OF FIRE CRACKLING)
ROTT: ...A pile of branches, needles and duff ignites, and smoke starts to fill the room.
(SOUNDBITE OF AIR VENTILATION)
ROTT: Outside of the room and away from the air pumps, Roberts meets with atmospheric chemist Bob Yokelson. Roberts is a research chemist with the National Oceanic and Atmospheric Administration. Yokelson is with the University of Montana. And together, they want to explain why this is so important. Yokelson starts.
BOB YOKELSON: There's three main things that affect the composition of the atmosphere. One is natural chemicals from plants.
ROTT: Think of the smell in a forest or a flower. Another is human-caused chemicals - exhaust from cars or industry.
YOKELSON: We call that anthropogenic. And then biomass burning - the fires on the planet.
ROTT: Or smoke. Yokelson says we know the least about smoke - what the chemicals from fires are doing to the ozone layer or atmosphere and...
YOKELSON: What are those particles doing to your lungs and what are they doing to the whole planet Earth.
ROTT: That information is relevant now more than ever. Wildfires are becoming more prevalent. They're burning longer and larger. And increasingly, the U.S. Forest Service is considering letting some of those fires burn when there are no structures or people threatened. Wildfire can be healthy for a forest, and by letting a small one burn, clearing out dead trees and brush, there's less fuel for the next one. To make that decision, though, Roberts says...
ROBERTS: You really need good science and chemical details about what that smoke does to the atmosphere.
ROTT: Because you wouldn't let a fire burn if you knew that the vegetation it was in and put up smoke and chemicals that were especially dangerous to humans or bad for the atmosphere, which brings us back to the research itself. The burning room is now opaque with smoke. Abigail Koss, a graduate student from the University of Colorado, tracks data coming in on a computer in an adjoining room.
ABIGAIL KOSS: So they lit the fire here.
ROTT: She's using a super sensitive spectrometer.
KOSS: This thing is like a robotic bloodhound almost...
ROTT: ...That can identify individual compounds in the smoke.
KOSS: The red line is formaldehyde, which you might be familiar with from high school biology.
ROTT: Yeah. It smells like pickling juice.
KOSS: Yeah, it's kind of gross.
ROTT: There's methanol and vanillin.
KOSS: You know all about vanillin from making cookies.
ROTT: Koss' experiment is only one of about 30 that is being done on the smoke. Together, they'll provide an unparalleled picture of what chemicals and particles are released by certain fires. And that information, Koss says, could soon help determine how or even if fires are fought around the country and the world. Nathan Rott, NPR News.
(SOUNDBITE OF SONG, "I DON'T WANT TO SET THE WORLD ON FIRE")
THE INK SPOTS: I don't want to set the world on fire.
[POST-BROADCAST CORRECTION: We incorrectly say that llama dung is an important fuel for heating homes in places such as Nepal. While dung is an important fuel around the world, in Nepal it mostly comes from yaks.] Transcript provided by NPR, Copyright NPR.