From Summary and Conclusions: '1. There are several different types of forest fires, each with distinct sets of emission characteristics. Emission factors for combustion products vary widely with fire behavior and fuel conditions. Whenever possible they should be expressed as ranges instead of single average values. 2. Over 90 percent of the mass of combustion products from forest fires are CO2 and water vapor. The major impact of forest fires on air quality come from minor and trace constituents. These are usually categorized under the conglomerate classes - hydrocarbons and particulate matter. 3. Within the hydrocarbon class, the low-molecular-weight gaseous species consist primarily of methane, ethylene, and acetylene. Several hundred organic vapor components are also emitted in lesser amounts. Included are many oxygenated classes, i.e. organic acids, aldehydes, and furans. many higher molecular weight, aliphatic, and aromatic hydrocarbons are also emitted. 4. Forest smoke particulate matter has a very high organic character. The benzene soluble organic (BSO) fraction is between 40 and 75 percent as compared to ambient air which averages 8 percent. 5. Included in the BSO fraction is polycyclic organic matter. In a series of laboratory studies, emission factors for benzo(a)pyrene ranged from 240 ng/g to 3,500 ng/g in backing fires and 38 ng/g to 100 ng/g for heading fires. Actual amounts formed depend on fire conditions and the residence time of combustible gases in the combustion zone. 6. Average physical size of particulate matter in forest fire smoke is approximately 0.1 micron. Between 90 and 95 percent of the mass of all particulate matter is below 1 micron. 7. The recent literature reports on forest fire particulate matter have been critically reviewed and found to vary by a factor of 100. Estimates range from 0.5 x 106 tons/yr to 54 x 106 tons/yr. 8. New national emission factors for forest fires have been proposed to replace the currently used value of 17 lbs/ton. The new values proposed are as follows: Wildfires 150 lbs/ton of fuel consumed Prescribed fires 50 lbs/ton of fuel consumed 9. Annual forest fire particulate matter production by geographic region and season is presented, and total particulate matter production from forest fires in the United States is estimated to be 3,930,000 tons/yr total.