Considerable research has been carried out to estimate the chemical composition and the amount of trace gases and particulate matter emitted during short-duration flaming and smoldering combustion of fuels in the fire-prone forest and grassland ecosystems. For other forest ecosystems, where long-duration residual smoldering combustion (RSC) significantly reduces forest fuels, errors in estimating total emissions have likely existed due to the lack of information, both on the extent and chemical compounds of these emissions. This research, funded by the Joint Fire Sciences Program (JFSP), investigates the smoke emissions produced by RSC, which may persist for hours or even days after the passage of the flame front. This project is the first large scale study to determine the emissions of important trace gases from common RSC prone fuel components such as logs, stumps, and duff. Studies were conducted in Alaska and the Southeastern and Western Regions of the US. Based on these measurements, combustion efficiencies and emission factors for the important carbon-containing trace gases have been calculated. Modified Combustion Efficiency (MCE) in this study was found to be significantly lower than those previously reported for flaming and short-duration smoldering phases of a wildland fire. The lower MCE is primarily the result of increased CO emissions. Emission factors for CH4 were also found to be generally higher, but no empirical relationships were found between the emission factors of CH4 and the emission factors of CO or MCE. Emissions of non-methane hydrocarbons (NMHC) were not correlated with CO and CH4 emissions, and were found to be about equal or lower than NMHC emission factors for the flaming and short-duration smoldering phases. Since prior estimates of RSC emissions were based on short-duration smoldering data, this new information will provide a more accurate estimate of the total emissions released from a wildland fire.