Outdoor wood boilers, known technically as hydronic heaters, can be found across much of rural America. They are popular among the wood burning community because they provide a way to heat with wood while keeping dirt and ash out of the home. Although air quality problems can arise with outdoor wood boilers, most of these problems can be minimized or avoided if the best management practices outlined in this factsheet are followed. These practices will decrease the amount of firewood utilized thereby increasing the economic advantage of wood energy and minimizing its environmental impact.