Smoke Management

Smoke can contribute to regional haze and may be considered an annoyance by recreationists and residents in scenic areas. Smoke is a nuisance when it irritates the eyes and mucous membranes of the nose and throat, or when it deposits soot on homes. Smoke exacerbates health problems for those with respiratory difficulty or other illnesses. Smoke is a safety hazard when it impedes visibility of drivers of motor vehicles. Problem smoke is chronic in the South because of three factors:

1. A lot of smoke is produced by wildfires and prescribed fires.
2. A lot of people live in interfaces between forests and urban areas.
3. Southern meteorology produces air masses that entrap smoke close to the ground at night.

Of the South’s 200 million acres of forest, 4 to 6 million acres burn annually. The area burned is the most in any region of the country. Prescribed burning is used to manage fuel loads and reduce the risk of catastrophic wildfire. The long growing season and warm, humid climate create conditions for rapid buildup of live and dead fuels, which contribute to greater smoke production when burned.

The southern forests are criss-crossed by a dense road network, even in predominantly rural areas. Population density is increasing in many areas of the South with an expanding interface between forests and dwellings. The population living within or near southern forests is greater than in other parts of the country where prescribed fire is widely used. In addition, many people travel through the South who are unaware of smoke and fog hazards.

Climate and weather contribute to problem smoke in several ways. First, prescribed burning is conducted when soil and litter are moist in order to avoid damaging tree roots. Fires in moist fuels burn less efficiently and smolder longer than fires in dry fuels, increasing smoke production. In addition, inefficient combustion produces less heat to carry smoke aloft, so smoke stays close to the ground. Second, shallow valley inversions can develop in the winter, trapping smoke near the ground. Weak drainage winds can carry smoke more than 10 miles, far enough to reach roadways in most areas.

See the following sections to learn more about the constituents of smoke, and what those conducting prescribed fire should do to reduce the impacts of smoke, or visit the section on smoke management in the Encyclopedia of Southern Fire Science.

• Components of smoke
• Mitigating smoke effects