Effect of temperature and humidity on total hydrocarbon emissions from Douglas-fir lumber

A small laboratory kiln was modified to measure total hydrocarbon emissions as Douglas-fir lumber was dried. A total hydrocarbon analyzer based on the flame ionization detection principle was used to measure concentration as propane equivalents and the exhaust flow rate after water was condensed from the gas was measured with an electronic mass flow meter. The methodology was similar to EPA Method 25A. The quantity of emissions increased with temperature in the range of 160?F (71?C) to 200?F (93?C). A 10?F (5.5?C) change in the wet-bulb depression among charges had no effect on the quantity of emissions. Emissions also increased with initial moisture content (MC) of the wood. The typical emission level reported as propane was 0.79 grams of hydrocarbon per kilogram of ovendry wood when wood was dried from green to 12 percent MC. This corresponds to approximately 1.47 pounds of hydrocarbon per 1,000 board feet.

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