Emissions of CO and NO for a porous medium burner adding the secondary air from the middle section were studied experimentally. The middle section is formed of a gap between the upstream section and downstream section of the porous foam ceramics in the burner with a middle hoop, into which the air can be poured from all around. The effects of equivalence ratios, flow rates of the mixture, and various fractions of secondary air on the emission of natural gas/air combustion were examined. The results show that a proper fraction of the secondary air could make the flame highly stable in the middle section within a wide range of flow rates, and have low emission of CO, specially for lower lean equivalence ratios. Values of NO emission for the flames in or around the middle zone could be perfectly low.