A goal of fire management in wilderness is to allow fire to play its natural ecological role without intervention. Unfortunately, most unplanned ignitions in wilderness are suppressed, in part because of the risk they might pose to values outside of the wilderness. We capitalize on recent advances in fire risk analysis to demonstrate a risk-based approach for revealing where unplanned ignitions in wilderness pose little risk to nonwilderness values and therefore where fire can be managed for its longer term ecological benefits. Using a large wilderness area as a case study, we conduct an exposure analysis and quantify the potential for unplanned ignitions inside the wilderness area to spread outside the wilderness boundary onto adjacent lands. Results show that, in general, ignitions that occur inside a large core area of the wilderness have very low likelihoods of escaping the wilderness boundary, especially early and late in the fire season. These "windows" may thus represent opportunities for allowing natural fire to occur. We discuss our approach in the broader context of spatial fire risk management and planning across public lands.