Faunal injury and mortality in wildland fires is a concern for wildlife and fire management although little work has been done on the mechanisms by which exposures cause their effects. In this paper, we use an integral plume model, field measurements, and models of carbon monoxide and heat effects to explore risk to tree-roosting bats during prescribed fires in mixed-oak forests of southeastern Ohio and eastern Kentucky. Tree-roosting bats are of interest primarily because of the need to mitigate risks for the endangered Indiana bat (Myotis sodalis), our focal species. Blood carboxyhemoglobin concentrations predicted from carbon monoxide data supplemented by model output only approached critical levels just above flames in the most intense fires. By contrast, an ear-heating model driven by plume model output suggested that injury to the bat's thermally thin ears would occur up to heights similar to those of foliage necrosis, an effect for which predictive relationships exist. Risks of heat injury increase with fireline intensity and decrease with both roost height and ambient wind. Although more information is needed on bat arousal from torpor and behavior during fires, strategies for reducing the risk of heat injury emerge from consideration of the underlying causal processes.