Smoke Management for Controlled Burns

What are the components of smoke from wildland burning?

All wildland fires produce smoke plumes that contain embers, particulates, nitrous oxides, and volatile organic compounds. In grassland prescribed fires, embers generally drop out rapidly, frequently within the burned area. Particulates and gasses, however, can cause air quality problems downwind if not managed.

Particulates are tiny bits of solids or liquids, and are designated as PM10 or PM2.5, which refers to the diameter of the particle as measured by its ability to pass through 10 microns or 2.5 microns filters, respectively. Because of their larger size, PM10 particles tend to drop out of the air more rapidly than PM2.5 particles.

Both types of particulate matter can cause breathing problems, especially for those with respiratory or circulatory diseases. PM2.5 is especially dangerous, as its small size allows it to be drawn deeply into the lungs. Both types of particulate matter are cleaned from the air by rain.

Nitrous oxides (NOx) and volatile organic compounds (VOC) are gasses released during combustion. Although they are not ozone, they combine in the presence of sunshine to form ozone. Ozone is not cleaned from the air by rainfall. It can disappear during the night, only to reform the following day. Ozone plumes hang together and are not dissipated by rain. Because of these characteristics, these plumes can travel hundreds of miles from the source.

What are the effects of smoke?

Ozone can also cause health problems for those with respiratory and cardiac diseases. Ozone and particulate matter can combine and cause an air quality problem called regional haze. This is an aesthetic as well as a health problem. Regional haze is most likely to form during low wind conditions and weather inversions.

Smoke combined with fog can create a visually impenetrable condition that is sometimes known as superfog. It tends to settle in low-lying areas such as valleys and stream corridors. Superfog is often associated with multiple fatal collisions, as motorists encounter the fog without warning and road conditions change from excellent visibility to near total darkness in a matter of seconds.

How can I reduce smoke from controlled burns?

When conducting prescribed burns, it’s important to be aware of problems that may result from the smoke you produce if you are near people who will be impacted by your smoke. If there are many prescribed fires burning at the same time in your area, the combined smoke plume from these fires can travel hundreds of miles and cause air quality problems in downwind areas. Burning on days when smoke dispersal is high will improve air quality both locally and downwind. Burning when fuels are dry will also increase combustion and reduce smoke production.

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