An experimental study of the effects of secondary air jets-injected perpendicular to the flame axis on the combustion of heavy fuel oil was investigated in a cylindrical refractory lined furnace of 500 kW. The design used here directed the secondary air jets at the end of the first stage combustion, thus maximizing the air jet energy and avoiding the unnecessary mixing of air with burned gases in the furnace adopted in low NOx burners. The performance of the new burner design was evaluated by quantifying the exhaust concentration levels of CO, and NOx. The experimental results demonstrated that NOx was reduced as much as 70% and practically 100% removal efficiency for CO.