Direct-fired recuperative thermal oxidizer cleans manufacturing exhaust streams that contain organic hydrocarbon contaminants. The oxidizer processes 21,000 scfm of exhaust and uses primary and secondary heat recovery subsystems to recapture heat energy for reuse. Primary recovery subsystem preheats the inlet airstream before it goes to the combustion chamber, resulting in energy savings. The secondary heat recovery system mixes a controlled portion of the clean, hot, oxidized exhaust air with room air to supply energy to a process oven. The remaining exhaust air is used to fire a wasteheat boiler that produces steam.