Systems and methods for treating wood and wood products, including a structure defining a wood treating zone, an air heating zone, a heated air supply zone, and a cooled air return zone. Heating units feed conduits defining one or more heat transfer surfaces and an indirect heat exchange substructure. The heated air supply zone includes left and right heated air plenums, and the cooled air return zone includes a return duct, all internal of the wood treating zone. A movable cart moves spaced apart, stacked wood products into and out of the wood heating zone. The cart and wood thereon fit closely within but do not touch the wood treating zone. An air blower internal of the heated air supply zone and in fluid communication with the air heating zone and the heated air supply zone recirculates air. An exhaust blower vents some of the cooled air.