A modular oven structure includes a frame, a circulation fan at a top of the frame, a tunnel air inlet chamber, a tunnel air return chamber, a tunnel drying chamber between the tunnel air inlet and tunnel air return chambers, a tunnel air inlet plate including air apertures and between the tunnel air inlet and tunnel drying chambers, a tunnel air return plate including air apertures and between the tunnel air return and tunnel drying chambers, a fan air inlet chamber above the tunnel drying chamber, a fan air outlet chamber between the fan air inlet chamber and the top of the frame, a heater, a temperature control system, and a control device. The temperature control system includes one or more temperature sensors in the tunnel air inlet, tunnel air return, and/or tunnel drying chamber.