A series of medium-scale smoke experiments were conducted at the University of California, Berkeley. Representative fuels, such as wood, asphalt roofing shingles, and liquid hydrocarbons, were burned as medium-scale fuel packages in the open, with no restriction on the ventilation. For some of the fuels, the experiments were also conducted in a burn room under limited ventilation conditions. The effects of different combustion conditions resulting from differences in fuel composition, geometry, and ventilation were determined.
Smoke emission factors measured for burning wood under well-ventilated conditions were in the range of 0.1 to 0.3%, but under limited ventilation conditions they increased an order of magnitude to the 2 to 3% range. Under well-ventilated conditions, the smoke emission factors measured for asphalt were in the 12% range and those for No. 2 fuel oil were in the 11% range. Burning in the compartment also affected the emission factors and smoke characteristics of fuel oil.
The results of the medium-scale experiments presented in this paper show that the smoke emission factors are not only dependent on the properties of a given fuel, but also on the environmental conditions under which the fuel was burned. Specifically, the influence of ventilation rate, fuel mass loss rate, temperature, and residence time are important. Although more research is required before a standardized medium-scale fire test to measure smoke production can be developed, the need for such a test standard is clearly demonstrated by these results.