OPEN-PATH FOURIER-TRANSFORM INFRARED STUDIES OF LARGE-SCALE LABORATORY BIOMASS FIRES

A series of nine large-scale, open fires was conducted in the Intermou ntain Fire Sciences Laboratory (IFSL) controlled-environment combustio n facility. The fuels were pure pine needles or sagebrush or mixed fue ls simulating forest-floor, ground fires; crown fires, broadcast burns ; and slash pile burns. Mid-infrared spectra of the smoke were recorde d throughout each fire by open path Fourier transform infrared (FTIR) spectroscopy at 0.12 cm(-1) resolution over a 3 m cross-stack pathleng th and analyzed to provide pseudocontinuous, simultaneous concentratio ns of up to 16 compounds. Simultaneous measurements were made of fuel mass loss, stack gas temperature, and total mass flow up the stack. Th e products detected are classified by the type of process that dominat es in producing them. Carbon dioxide is the dominant emission of (and primarily produced by) flaming combustion, from which we also measure nitric oxide, nitrogen dioxide, sulfur dioxide, and most of the water vapor from combustion and fuel moisture. Carbon monoxide is the domina nt emission formed primarily by smoldering combustion from which we al so measure carbon dioxide, methane, ammonia, and ethane. A significant fraction of the total emissions is unoxidized pyrolysis products; exa mples are methanol, formaldehyde, acetic and formic acid, ethene (ethy lene), ethyne (acetylene), and hydrogen cyanide. Relatively few previo us data exist for many of these compounds and they are likely to have an important but as yet poorly understood role in plume chemistry. Lar ge differences in emissions occur from different fire and fuel types, and the observed temporal behavior of the emissions is found to depend strongly on the fuel bed and product type.