Data from surveys of 1977-1979 indicate that firewood usage tends to vary inversely with population density, resulting in an implied limit to the density of usage. Tests of wood stoves indicate that emissions of particulates vary inversely with heat demand, such that nighttime emissions at low combustion rates may be worse than those during maximum heat demand conditions. Finally, atmospheric dispersion rates are coupled to the driving forces of space heating so that nighttime emissions tend to have a disproportionately large impact on ambient air quality. All of these factors must be considered jointly in order to perform a meaningful assessment of the air quality impacts of increased residential wood fuel use; the results indicate that in flat terrain primary ambient standards are not threatened by residential wood combustion.